Heidelberg Joint Astronomical Colloquium
Upcoming events
Chemical Enrichments in the Milky Way and Its Accreted Dwarf Galaxies
Dr Tadafumi Matsuno (Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The Universe began with a simple chemical composition of hydrogen, helium, and a small amount of lithium. Since then, this composition has evolved thanks to nucleosynthesis events. Low-mass stars serve as fossil records of these chemical enrichments, as their surface composition remains largely unchanged throughout their long lifetimes. In this talk, I aim to demonstrate how stellar chemical abundances can enhance our understanding of stellar populations in the Milky Way and the origin of elements. I will focus on the stellar halo of the Milky Way, where we can observe stellar populations that formed outside the Milky Way and those that formed in the early Universe. I will first review recent progress in this field, particularly on the discoveries of spatial and kinematic substructures from Gaia data. Next, I will discuss the astrophysical implications derived from the chemical abundances of stars in these substructures, including insights into the host of a 33 solar-mass black hole, disrupted globular clusters, and the Milky Way's galaxy accretion history. I will emphasize that high-precision chemical abundance measurements are crucial in obtaining these insights. Finally, while characterizing stellar populations through chemical abundance relies on our knowledge of nucleosynthesis, I will illustrate that observational constraints on chemical enrichment histories of stellar populations provide valuable constraints on the origin of elements. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Tadafumi Matsuno (Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
The Universe began with a simple chemical composition of hydrogen, helium, and a small amount of lithium. Since then, this composition has evolved thanks to nucleosynthesis events. Low-mass stars serve as fossil records of these chemical enrichments, as their surface composition remains largely unchanged throughout their long lifetimes. In this talk, I aim to demonstrate how stellar chemical abundances can enhance our understanding of stellar populations in the Milky Way and the origin of elements. I will focus on the stellar halo of the Milky Way, where we can observe stellar populations that formed outside the Milky Way and those that formed in the early Universe. I will first review recent progress in this field, particularly on the discoveries of spatial and kinematic substructures from Gaia data. Next, I will discuss the astrophysical implications derived from the chemical abundances of stars in these substructures, including insights into the host of a 33 solar-mass black hole, disrupted globular clusters, and the Milky Way's galaxy accretion history. I will emphasize that high-precision chemical abundance measurements are crucial in obtaining these insights. Finally, while characterizing stellar populations through chemical abundance relies on our knowledge of nucleosynthesis, I will illustrate that observational constraints on chemical enrichment histories of stellar populations provide valuable constraints on the origin of elements. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Title to be announced
Dr Daniela Huppenkothen (Netherlands Institute for Space Research, Leiden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Dr Daniela Huppenkothen (Netherlands Institute for Space Research, Leiden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
The atmospheres of discs and planets
Professor Barbara Ercolano (University Observatory, Ludwig-Maximilians University Munich.)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The gaseous atmospheres of extrasolar planets and those of their birth environments, the protoplanetary discs, may hold the key to understanding the observed diversity of these distant worlds and might provide important insights on fundamental questions, including habitability. In this talk I will review the results of recent efforts to connect the protoplanetary disc evolution, driven by their central star, to the formation of planets. Special attention will be given to outflows and what can be/ has been learnt from them. Some of the unanswered questions, rely on the understanding of the chemical composition of atmospheric gas, particularly with regards to important species like (polycyclic aromatic) hydrocarbons, that control the thermodynamics in the far ultra-violet regime and play an important role in the coupling of the atmospheric gas to magnetic fields. The same molecules may play a very important role in the evolution of planetary atmospheres. Current and future efforts to constrain their abundances in discs and planets will also be reviewed. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Ercolano will be available for meetings by arrangement with her host, Kees Dullemond (dullemond@uni-heidelberg.de).
Professor Barbara Ercolano (University Observatory, Ludwig-Maximilians University Munich.)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The gaseous atmospheres of extrasolar planets and those of their birth environments, the protoplanetary discs, may hold the key to understanding the observed diversity of these distant worlds and might provide important insights on fundamental questions, including habitability. In this talk I will review the results of recent efforts to connect the protoplanetary disc evolution, driven by their central star, to the formation of planets. Special attention will be given to outflows and what can be/ has been learnt from them. Some of the unanswered questions, rely on the understanding of the chemical composition of atmospheric gas, particularly with regards to important species like (polycyclic aromatic) hydrocarbons, that control the thermodynamics in the far ultra-violet regime and play an important role in the coupling of the atmospheric gas to magnetic fields. The same molecules may play a very important role in the evolution of planetary atmospheres. Current and future efforts to constrain their abundances in discs and planets will also be reviewed. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Ercolano will be available for meetings by arrangement with her host, Kees Dullemond (dullemond@uni-heidelberg.de).
The beating hearts of galaxies: supermassive black hole feedback probed by X-ray spectroscopy
Dr Aurora Simionescu (Leiden Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Dr Aurora Simionescu (Leiden Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Title to be announced
Professor Ilse De Looze (University of Ghent)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Professor Ilse De Looze (University of Ghent)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
The Universe in multi-color: Astronomy at the dawn of intensity mapping and AI
Dr Caroline Heneka (Institute of Theoretical Physics, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Dr Caroline Heneka (Institute of Theoretical Physics, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Title to be announced
Dr Sylvia Ekstroem (University of Geneva)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Dr Sylvia Ekstroem (University of Geneva)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Planet Migration in Dusty Protoplanetary Disks
Professor Martin Pessah (Niels Bohr Institute, Copenhagen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Fast inward migration of planetary cores embedded in gaseous disks is a common problem in the current planet formation paradigm. Even though dust is ubiquitous in protoplanetary disks, its dynamical role in the migration history of planetary embryos has not been considered until recently. In this talk, I will show that a planetesimal embedded in a dusty disk leads to an asymmetric dust-density distribution that can exert a net torque under conditions relevant to planetary embryos up to several Earth masses. Building on the results or a large suite of numerical simulations for measuring this dust torque under a wide range of conditions, I will present the first study showing that dust torques can have a significant impact on the migration and formation history of planetary embryos. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Prof. Pessah will be available for meetings by arrangement with his host, Maria Bergemann (bergemann@mpia.de).
Professor Martin Pessah (Niels Bohr Institute, Copenhagen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Fast inward migration of planetary cores embedded in gaseous disks is a common problem in the current planet formation paradigm. Even though dust is ubiquitous in protoplanetary disks, its dynamical role in the migration history of planetary embryos has not been considered until recently. In this talk, I will show that a planetesimal embedded in a dusty disk leads to an asymmetric dust-density distribution that can exert a net torque under conditions relevant to planetary embryos up to several Earth masses. Building on the results or a large suite of numerical simulations for measuring this dust torque under a wide range of conditions, I will present the first study showing that dust torques can have a significant impact on the migration and formation history of planetary embryos. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Prof. Pessah will be available for meetings by arrangement with his host, Maria Bergemann (bergemann@mpia.de).
From cosmic web to molecular clouds: the multiple scales of galaxy evolution
Professor Amelie Saintonge (Max Planck Institut for Radioastronomy and University College London)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The interstellar medium plays a central role in the galaxy evolution process; it is the reservoir that fuels galaxy growth via star formation, the repository of material formed by these stars, and a sensitive tracer of internal and external processes that affect entire galaxies (e.g. accretion and feedback). In this overview talk, I will discuss how observations of the interstellar medium are shedding light on the vast range of physics and scales at play in the star formation and galaxy evolution processes, using results from recent observing campaigns with (sub)mm/radio facilities (IRAM, ALMA, JCMT, APEX) as well as large optical spectroscopic surveys (DESI). By connecting these observations with theory and simulations, a picture emerges where galaxy evolution is driven by gas availability on galactic- and molecular cloud-scales and the efficiency of the star formation process out of this gas, depending on local conditions in the interstellar medium. These results highlight the multi-scale nature of star formation and galaxy evolution, and help draw a path forward to understand mass assembly in the Universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Saintonge will be available for meetings by arrangement with her host, Dominika Wylezalek (dominika.wylezalek@uni-heidelberg.de).
Professor Amelie Saintonge (Max Planck Institut for Radioastronomy and University College London)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The interstellar medium plays a central role in the galaxy evolution process; it is the reservoir that fuels galaxy growth via star formation, the repository of material formed by these stars, and a sensitive tracer of internal and external processes that affect entire galaxies (e.g. accretion and feedback). In this overview talk, I will discuss how observations of the interstellar medium are shedding light on the vast range of physics and scales at play in the star formation and galaxy evolution processes, using results from recent observing campaigns with (sub)mm/radio facilities (IRAM, ALMA, JCMT, APEX) as well as large optical spectroscopic surveys (DESI). By connecting these observations with theory and simulations, a picture emerges where galaxy evolution is driven by gas availability on galactic- and molecular cloud-scales and the efficiency of the star formation process out of this gas, depending on local conditions in the interstellar medium. These results highlight the multi-scale nature of star formation and galaxy evolution, and help draw a path forward to understand mass assembly in the Universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Saintonge will be available for meetings by arrangement with her host, Dominika Wylezalek (dominika.wylezalek@uni-heidelberg.de).
Past events
2024-11-19
16:30
16:30
The JASMINE mission
Professor Daisuke Kawata (University College London)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE) is a selected ISAS/JAXA science space mission. JASMINE has two main science goals. One is Galactic archaeology with a Galactic Centre survey, which aims to reveal the Milky Way’s central core (Rgc<~200 pc) structure and formation history from Gaia-level (?25 ?as) astrometry in the near-infrared (NIR) Hw-band (1.0–1.6?m). The other is an exoplanet survey, which aims to discover transiting Earth-like exoplanets in the habitable zone from NIR time-series photometry of M dwarfs when the Galactic Centre is not accessible. JASMINE will be the first dedicated NIR astrometry space mission and provide precise astrometric information on the stars in the Galactic Centre, taking advantage of the significantly lower extinction in the NIR. The precise astrometry is obtained by taking many short-exposure images. Hence, the JASMINE Galactic Centre survey data will be valuable for studies of exoplanet transits, asteroseismology, variable stars, and microlensing studies, including discovery of (intermediate-mass) black holes. We introduce the mission and review the science prospects of JASMINE. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Kawata will be available for meetings by arrangement with his host, Michael Biermann (biermann@ari.uni-heidelberg.de).
Professor Daisuke Kawata (University College London)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE) is a selected ISAS/JAXA science space mission. JASMINE has two main science goals. One is Galactic archaeology with a Galactic Centre survey, which aims to reveal the Milky Way’s central core (Rgc<~200 pc) structure and formation history from Gaia-level (?25 ?as) astrometry in the near-infrared (NIR) Hw-band (1.0–1.6?m). The other is an exoplanet survey, which aims to discover transiting Earth-like exoplanets in the habitable zone from NIR time-series photometry of M dwarfs when the Galactic Centre is not accessible. JASMINE will be the first dedicated NIR astrometry space mission and provide precise astrometric information on the stars in the Galactic Centre, taking advantage of the significantly lower extinction in the NIR. The precise astrometry is obtained by taking many short-exposure images. Hence, the JASMINE Galactic Centre survey data will be valuable for studies of exoplanet transits, asteroseismology, variable stars, and microlensing studies, including discovery of (intermediate-mass) black holes. We introduce the mission and review the science prospects of JASMINE. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Kawata will be available for meetings by arrangement with his host, Michael Biermann (biermann@ari.uni-heidelberg.de).
2024-11-12
16:30
16:30
StarDance: the non-canonical evolution of stars in clusters
Professor Elena Pancino (University of Florence)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Thanks to their ubiquity, brightness, and the fact that they are made of stars with similar properties, star clusters have been used as astrophysical laboratories or test particles in an impressive range of research domains. However, we still do not understand fundamental details of their formation and evolution. In spite of recent technological progress, a list of unsolved problems and apparently isolated mysteries has been accumulating over time, some standing since decades. Among them, the existence of multiple stellar populations in globular clusters, with different chemistry, has challenged generations of researchers. They are not the result of classical galactic chemical evolution, mostly mediated by supernovae, and they jeopardize the use of clusters as simple stellar population templates for extragalactic studies. Given the mounting problems faced by the most favored scenarios to explain multiple populations, it is now time to revisit the foundations of our current thinking. New results show that: (i) the peculiarities in the chemistry of multiple populations are not limited to the oldest globular clusters; (ii) they can be transient in the evolution of individual cluster stars; and most importantly (iii) binary interactions and fast stellar rotation cannot be neglected in the study of star clusters and do have the capability to produce the observed chemistry. The StarDance hypothesis assumes that multiple stellar populations and five other non-canonical stellar populations (extreme horizontal branch stars and hot sub-dwarfs; extended main sequence turn-offs; red stragglers and sub-subgiants; lithium-rich stars; and blue stragglers) are caused by the interplay between stellar rotation and binary interactions, that are greatly enhanced in the special environment of star cluster, with spectacular results. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Pancino will be available for meetings by arrangement with her host, Michela Mapelli (mapelli@uni-heidelberg.de).
Professor Elena Pancino (University of Florence)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Thanks to their ubiquity, brightness, and the fact that they are made of stars with similar properties, star clusters have been used as astrophysical laboratories or test particles in an impressive range of research domains. However, we still do not understand fundamental details of their formation and evolution. In spite of recent technological progress, a list of unsolved problems and apparently isolated mysteries has been accumulating over time, some standing since decades. Among them, the existence of multiple stellar populations in globular clusters, with different chemistry, has challenged generations of researchers. They are not the result of classical galactic chemical evolution, mostly mediated by supernovae, and they jeopardize the use of clusters as simple stellar population templates for extragalactic studies. Given the mounting problems faced by the most favored scenarios to explain multiple populations, it is now time to revisit the foundations of our current thinking. New results show that: (i) the peculiarities in the chemistry of multiple populations are not limited to the oldest globular clusters; (ii) they can be transient in the evolution of individual cluster stars; and most importantly (iii) binary interactions and fast stellar rotation cannot be neglected in the study of star clusters and do have the capability to produce the observed chemistry. The StarDance hypothesis assumes that multiple stellar populations and five other non-canonical stellar populations (extreme horizontal branch stars and hot sub-dwarfs; extended main sequence turn-offs; red stragglers and sub-subgiants; lithium-rich stars; and blue stragglers) are caused by the interplay between stellar rotation and binary interactions, that are greatly enhanced in the special environment of star cluster, with spectacular results. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Pancino will be available for meetings by arrangement with her host, Michela Mapelli (mapelli@uni-heidelberg.de).
2024-11-05
16:30
16:30
The Nature of "Little Red Dots"
Professor Jenny Greene (Princeton University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
One of the most surprising results from JWST has been the discovery of a large population of compact red sources at z>4, with very red rest-frame optical colors, blue UV slopes, and broad Balmer lines. The compact sizes and luminous broad lines strongly suggest that these objects are powered by accreting supermassive black holes, but their lack of evidence for X-ray emission or hot dust in the mid-infrared calls that conclusion into question. Regardless, their high number densities (~2-5% of the galaxy population) makes them an important new contribution to the high-redshift galaxy census. I will discuss our ongoing efforts to understand the nature of this population, and what they may teach us about the growth of black holes and/or galaxies. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Morabito will be available for meetings by arrangement with her host, Nadine Neumayer (neumayer@mpia.de).
Professor Jenny Greene (Princeton University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
One of the most surprising results from JWST has been the discovery of a large population of compact red sources at z>4, with very red rest-frame optical colors, blue UV slopes, and broad Balmer lines. The compact sizes and luminous broad lines strongly suggest that these objects are powered by accreting supermassive black holes, but their lack of evidence for X-ray emission or hot dust in the mid-infrared calls that conclusion into question. Regardless, their high number densities (~2-5% of the galaxy population) makes them an important new contribution to the high-redshift galaxy census. I will discuss our ongoing efforts to understand the nature of this population, and what they may teach us about the growth of black holes and/or galaxies. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Morabito will be available for meetings by arrangement with her host, Nadine Neumayer (neumayer@mpia.de).
2024-10-29
16:30
16:30
Radio stars and exoplanets: Discovering the space weather of other worlds
Dr Joseph Callingham (Astron/Leiden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
One key question that astronomy is attempting to answer is whether there are habitable planets around stars other than our Sun. While we have entered an era where identifying nearby exoplanets has become standard, discerning whether the environmental conditions dictated by the host stars are suitable for life has proved far more elusive. The detection o low-frequency radio emission from an M dwarf or an exoplanet provides a direct probe of extrasolar space weather and the planet's magnetic field - information crucial for assessing the potential habitability of the planet. In this talk, I will outline my radio survey of stellar systems, with a focus on our recent detection of strong, highly circularly polarised low-frequency radio emission associated with nearby stars - the expected signpost of star-exoplanet interactions. I will discuss how our survey represents the most comprehensive observations of stellar systems at low frequencies, and the implications of this new population in understanding the magnetosphere of M dwarfs and exoplanetary magnetic fields. I will conclude with our progress in determining the expected periodicity of the radio emission from star-planet interactions and search for stellar coronal mass ejections. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr. Callingham will be available for meetings by arrangement with his host, Richard Tuffs (Richard.Tuffs@mpi-hd.mpg.de).
Dr Joseph Callingham (Astron/Leiden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
One key question that astronomy is attempting to answer is whether there are habitable planets around stars other than our Sun. While we have entered an era where identifying nearby exoplanets has become standard, discerning whether the environmental conditions dictated by the host stars are suitable for life has proved far more elusive. The detection o low-frequency radio emission from an M dwarf or an exoplanet provides a direct probe of extrasolar space weather and the planet's magnetic field - information crucial for assessing the potential habitability of the planet. In this talk, I will outline my radio survey of stellar systems, with a focus on our recent detection of strong, highly circularly polarised low-frequency radio emission associated with nearby stars - the expected signpost of star-exoplanet interactions. I will discuss how our survey represents the most comprehensive observations of stellar systems at low frequencies, and the implications of this new population in understanding the magnetosphere of M dwarfs and exoplanetary magnetic fields. I will conclude with our progress in determining the expected periodicity of the radio emission from star-planet interactions and search for stellar coronal mass ejections. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr. Callingham will be available for meetings by arrangement with his host, Richard Tuffs (Richard.Tuffs@mpi-hd.mpg.de).
2024-10-22
16:30
16:30
The highest resolution at the lowest frequencies: what LOFAR can tell us about active galactic nuclei
Professor Leah Morabito (Durham University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The International LOFAR Telescope (ILT) has baselines up to 2,000 km, making it capable of achieving sub-arcsecond resolution at frequencies below 200 MHz. This makes it an incredible instrument for studying active galactic nuclei (AGN), both in terms of unique statistical studies and detailed studies of individual sources. However, high resolution imaging at low frequencies is technically and logistically challenging: the ILT's phased-array design, the ionosphere, the lack of suitable calibrator information, and existing software tools all conspire to make it difficult to achieve the highest possible resolution at MHz frequencies. Over the past few years, we have built on our growing understanding of these challenges to design a suitable calibration strategy, which is now implemented in a publicly available pipeline. In the past year this has enabled us to more than double the number of scientific papers published using sub-arcsecond imaging < 200 MHz, including cutting edge work to image the entire 5 square degree field of view of the ILT at sub-arcsecond resolution. I will provide an overview of how we overcome these challenges and then focus on examples of our breakthrough successes and recent science results. I will focus particularly on how we can use this unique combination of resolution, frequency, and field of view to diagnose the radio emission in galaxies and understand the radio emission mechanisms in radio quiet AGN, which is a major open question. I will finish by providing an overview on current and future plans, including a Northen sky survey which will have higher resolution than any previous wide-area radio survey. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Morabito will be available for meetings by arrangement with her host, Eduardo Banados (banados@mpia.de).
Professor Leah Morabito (Durham University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
The International LOFAR Telescope (ILT) has baselines up to 2,000 km, making it capable of achieving sub-arcsecond resolution at frequencies below 200 MHz. This makes it an incredible instrument for studying active galactic nuclei (AGN), both in terms of unique statistical studies and detailed studies of individual sources. However, high resolution imaging at low frequencies is technically and logistically challenging: the ILT's phased-array design, the ionosphere, the lack of suitable calibrator information, and existing software tools all conspire to make it difficult to achieve the highest possible resolution at MHz frequencies. Over the past few years, we have built on our growing understanding of these challenges to design a suitable calibration strategy, which is now implemented in a publicly available pipeline. In the past year this has enabled us to more than double the number of scientific papers published using sub-arcsecond imaging < 200 MHz, including cutting edge work to image the entire 5 square degree field of view of the ILT at sub-arcsecond resolution. I will provide an overview of how we overcome these challenges and then focus on examples of our breakthrough successes and recent science results. I will focus particularly on how we can use this unique combination of resolution, frequency, and field of view to diagnose the radio emission in galaxies and understand the radio emission mechanisms in radio quiet AGN, which is a major open question. I will finish by providing an overview on current and future plans, including a Northen sky survey which will have higher resolution than any previous wide-area radio survey. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Morabito will be available for meetings by arrangement with her host, Eduardo Banados (banados@mpia.de).
2024-07-23
16:30
16:30
Tracing Star Formation Across Scales: A Case Study in the Solar Neighborhood
Professor Catherine Zucker (Center for Astrophysics, Harvard & Smithsonian)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The processes regulating star formation in galaxies act across many orders of magnitude in spatial scale. Thus, a key challenge in understanding star formation is bridging the small-scale physics within molecular clouds and the large-scale structure of spiral galaxies. Fully constraining the physics of star formation across these scales requires constraints on both the 3D spatial structure and dynamical state of the interstellar medium (ISM), the combination of which has been an essentially unknown quantity in the field of star formation research. In this talk, I will discuss ongoing efforts to construct high-dimensional models of the ISM in the solar neighborhood by combining data science and visualization techniques with wide-field photometric, astrometric, and spectroscopic surveys. On kiloparsec scales, I will discuss how "3D dust mapping" has enabled constraints on the global distribution of molecular clouds, revealing new links between clouds long thought to be isolated and challenging fundamental assumptions about the shape and position of a nearby spiral arm. On parsec scales, I will show how combining 3D dust mapping with the 3D space motions of young stars can explain the origin of local star formation as being driven by the expansion of the Local Bubble, the nearest superbubble to the Sun. Finally, on au-scales, I will discuss the implications that the Sun’s trajectory through the ISM has for the properties of the heliosphere and the geological record here on Earth. I will conclude by previewing the opportunities enabled by future infrared surveys, including SDSS-V and Roman, which together will pave the way for a unified understanding of the multi-scale physical processes shaping star formation in diverse environments across the Milky Way’s disk. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor Zucker will be available for meetings by arrangement with her host, Ralf Klessen (klessen@uni-heidelberg.de)
Professor Catherine Zucker (Center for Astrophysics, Harvard & Smithsonian)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
The processes regulating star formation in galaxies act across many orders of magnitude in spatial scale. Thus, a key challenge in understanding star formation is bridging the small-scale physics within molecular clouds and the large-scale structure of spiral galaxies. Fully constraining the physics of star formation across these scales requires constraints on both the 3D spatial structure and dynamical state of the interstellar medium (ISM), the combination of which has been an essentially unknown quantity in the field of star formation research. In this talk, I will discuss ongoing efforts to construct high-dimensional models of the ISM in the solar neighborhood by combining data science and visualization techniques with wide-field photometric, astrometric, and spectroscopic surveys. On kiloparsec scales, I will discuss how "3D dust mapping" has enabled constraints on the global distribution of molecular clouds, revealing new links between clouds long thought to be isolated and challenging fundamental assumptions about the shape and position of a nearby spiral arm. On parsec scales, I will show how combining 3D dust mapping with the 3D space motions of young stars can explain the origin of local star formation as being driven by the expansion of the Local Bubble, the nearest superbubble to the Sun. Finally, on au-scales, I will discuss the implications that the Sun’s trajectory through the ISM has for the properties of the heliosphere and the geological record here on Earth. I will conclude by previewing the opportunities enabled by future infrared surveys, including SDSS-V and Roman, which together will pave the way for a unified understanding of the multi-scale physical processes shaping star formation in diverse environments across the Milky Way’s disk. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor Zucker will be available for meetings by arrangement with her host, Ralf Klessen (klessen@uni-heidelberg.de)
2024-07-16
16:30
16:30
Local Galaxies as Cosmic Bridges
Dr Claus Leitherer (Space Telescope Science Institute, Baltimore)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Hot massive stars are observed both individually in the Galaxy and in its nearest neighbors, as well as in the integrated light of galaxies at cosmic dawn. In this talk I focus on massive stars and populations in galaxies at distance of a few to hundreds of Mpc. These “Local” galaxies are at a sweet spot where detailed studies of stellar properties are still feasible but at the same time global galaxy properties are available as well. Local galaxies can therefore serve as bridges between stellar astrophysics and observational cosmology. I will discuss our ongoing research on these galaxies and present new results on the stellar properties, chemical abundances and evolution, galactic outflows and escaping ionizing radiation into the intergalactic medium. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr. Leitherer will be available for meetings by arrangement with his host, Andreas Sander (andreas.sander@uni-heidelberg.de).
Dr Claus Leitherer (Space Telescope Science Institute, Baltimore)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Hot massive stars are observed both individually in the Galaxy and in its nearest neighbors, as well as in the integrated light of galaxies at cosmic dawn. In this talk I focus on massive stars and populations in galaxies at distance of a few to hundreds of Mpc. These “Local” galaxies are at a sweet spot where detailed studies of stellar properties are still feasible but at the same time global galaxy properties are available as well. Local galaxies can therefore serve as bridges between stellar astrophysics and observational cosmology. I will discuss our ongoing research on these galaxies and present new results on the stellar properties, chemical abundances and evolution, galactic outflows and escaping ionizing radiation into the intergalactic medium. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr. Leitherer will be available for meetings by arrangement with his host, Andreas Sander (andreas.sander@uni-heidelberg.de).
2024-07-09
16:30
16:30
Gravitational-wave Paleontology: a new frontier to study the Formation, Lives, and Deaths of Massive Stars Across Cosmic Time
Dr. Floor Broekgaarden (Columbia University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
We are on the precipice of the Big Data gravitational-wave era. Pairs of stellar-mass black holes and neutron stars across our vast universe occasionally merge, unleashing bursts of gravitational waves that can now be detected here on Earth. Over the next few years, the population of detected mergers will rapidly increase from about a hundred today to millions of detections per year as new observing runs and next-generation detectors provide data with ever-increasing precision and to larger distances, pushing the reach of gravitational-wave astronomy to the edge of the observable universe! Most excitingly, this wealth of data will provide an unprecedented probe of the physics of black holes and neutron stars, and of the evolution of the binary massive stars that once formed them. This could open the new frontier of ‘gravitational-wave paleontology’: studying massive stars and binary evolution from their ‘remnant’ compact object mergers, with the goal of answering some of the biggest open questions in astrophysics today: How do these gravitational-wave sources form? What can we learn from them about the formation, lives, and explosive deaths of massive stars across cosmic time? How do these sources help to enrich the universe with heavy metals? In this talk, I will outline the main bottleneck in this field: the “Progenitor Uncertainty Challenge”. I will discuss how my research group is leading efforts to identify, quantify, and eventually overcome this challenge with the aim to open the new frontier of gravitational-wave paleontology and make unprecedented discoveries about massive stars across cosmic time from gravitational waves, as well as from other upcoming multi-wavelength and multi-messenger observations. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Dr Broekgaarden will be available for meetings by arrangement with her host, Michela Mapelli (mapelli@uni-heidelberg.de)
Dr. Floor Broekgaarden (Columbia University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
We are on the precipice of the Big Data gravitational-wave era. Pairs of stellar-mass black holes and neutron stars across our vast universe occasionally merge, unleashing bursts of gravitational waves that can now be detected here on Earth. Over the next few years, the population of detected mergers will rapidly increase from about a hundred today to millions of detections per year as new observing runs and next-generation detectors provide data with ever-increasing precision and to larger distances, pushing the reach of gravitational-wave astronomy to the edge of the observable universe! Most excitingly, this wealth of data will provide an unprecedented probe of the physics of black holes and neutron stars, and of the evolution of the binary massive stars that once formed them. This could open the new frontier of ‘gravitational-wave paleontology’: studying massive stars and binary evolution from their ‘remnant’ compact object mergers, with the goal of answering some of the biggest open questions in astrophysics today: How do these gravitational-wave sources form? What can we learn from them about the formation, lives, and explosive deaths of massive stars across cosmic time? How do these sources help to enrich the universe with heavy metals? In this talk, I will outline the main bottleneck in this field: the “Progenitor Uncertainty Challenge”. I will discuss how my research group is leading efforts to identify, quantify, and eventually overcome this challenge with the aim to open the new frontier of gravitational-wave paleontology and make unprecedented discoveries about massive stars across cosmic time from gravitational waves, as well as from other upcoming multi-wavelength and multi-messenger observations. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Dr Broekgaarden will be available for meetings by arrangement with her host, Michela Mapelli (mapelli@uni-heidelberg.de)
2024-07-02
16:30
16:30
Peering Inside Giants: How Solar System information and JWST Data Transforms Our Understanding of Exoplanet Interiors
Professor Yamila Miguel (Leiden Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
We are at a unique time to study giant exoplanets. With more than 5000 exoplanets found and facilities like the James Webb Space Telescope that provide unprecedented data on their atmospheres, we moved from an era of discovery to an era of exoplanet characterisation. At the same time, precise measurements from missions like Juno and Cassini to Jupiter and Saturn, lead to a different way of looking at giant planet interior structures, with inhomogeneous interiors that have not been used in exoplanet modelling before. This is an exceptional time to combine the detailed information on the solar system's giant planets with the large amount of data from exoplanets to get a better understanding of planetary physics and a better comprehension of planet formation and evolution. In this talk, I will present the last advancements in our knowledge of the giants in the solar system provided by Juno and Cassini missions. Furthemore, I will introduce the first retrieval for exoplanet interiors using next-generation models that are grounded in data from Jupiter and Saturn. These models not only shed light on bulk metallicities but also provide information on core masses and the internal distribution of metals. Using as input planetary masses, radii, atmospheric data provided by JWST and Love numbers (when available), we demonstrate how this integrated methodology leads to the derivation of more realistic interior structures, opening the door to a new generation of interior models for giant exoplanets. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Miguel will be available for meetings by arrangement with her host Dr Lorena Acuna (acuna@mpia.de).
Professor Yamila Miguel (Leiden Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
We are at a unique time to study giant exoplanets. With more than 5000 exoplanets found and facilities like the James Webb Space Telescope that provide unprecedented data on their atmospheres, we moved from an era of discovery to an era of exoplanet characterisation. At the same time, precise measurements from missions like Juno and Cassini to Jupiter and Saturn, lead to a different way of looking at giant planet interior structures, with inhomogeneous interiors that have not been used in exoplanet modelling before. This is an exceptional time to combine the detailed information on the solar system's giant planets with the large amount of data from exoplanets to get a better understanding of planetary physics and a better comprehension of planet formation and evolution. In this talk, I will present the last advancements in our knowledge of the giants in the solar system provided by Juno and Cassini missions. Furthemore, I will introduce the first retrieval for exoplanet interiors using next-generation models that are grounded in data from Jupiter and Saturn. These models not only shed light on bulk metallicities but also provide information on core masses and the internal distribution of metals. Using as input planetary masses, radii, atmospheric data provided by JWST and Love numbers (when available), we demonstrate how this integrated methodology leads to the derivation of more realistic interior structures, opening the door to a new generation of interior models for giant exoplanets. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Prof. Miguel will be available for meetings by arrangement with her host Dr Lorena Acuna (acuna@mpia.de).
2024-06-25
16:30
16:30
Re-discovering the Milky Way: a journey through data and simulations
Dr. Sergey Khoperskov (Leibniz-Institut für Astrophysik Potsdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Understanding galaxy formation and evolution stands as a fundamental objective in modern scientific research. However, a comprehensive observational and theoretical framework that can account for the vast range of properties observed in galaxies throughout the Universe remains elusive. In this context, the Milky Way is special, as it provides the unique opportunity to investigate complex galaxy assembly processes by studying its resolved stellar populations. Nowadays, knowledge about all Galactic components, from the halo to the disc(s) and bulge, is undergoing a profound revolution thanks to the ESA’s astrometric mission Gaia. Gaia has provided detailed measurements of stellar positions, motions, and parallax for over a billion stars, offering a comprehensive map of our galaxy. Complementing this, spectroscopic data from surveys such as APOGEE, GALAH, GES, and others provide us with stellar parameters, chemical abundances, ages and velocities. These are vital for understanding the mutual interconnection between different Galactic components. In this talk, I aim to demonstrate what we have learned about the Milky Way using the synergy between large observational data sets, various modeling techniques and state-of-the-art galaxy formation simulations. This integrated approach has led to an in-depth understanding of the disc mass assembly history, the impact of the bar and spiral arms, the formation and present-day structure of the bulge, and the build-up of the Milky Way's stellar halo. Finally, I will discuss how our detailed knowledge about the Milky Way can be used to fill the gaps in our picture of galactic evolution in general. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr Khoperskov will be available for meetings by arrangement with his host Dr Guiglion Guillaume (guiglion@mpia.de).
Dr. Sergey Khoperskov (Leibniz-Institut für Astrophysik Potsdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Understanding galaxy formation and evolution stands as a fundamental objective in modern scientific research. However, a comprehensive observational and theoretical framework that can account for the vast range of properties observed in galaxies throughout the Universe remains elusive. In this context, the Milky Way is special, as it provides the unique opportunity to investigate complex galaxy assembly processes by studying its resolved stellar populations. Nowadays, knowledge about all Galactic components, from the halo to the disc(s) and bulge, is undergoing a profound revolution thanks to the ESA’s astrometric mission Gaia. Gaia has provided detailed measurements of stellar positions, motions, and parallax for over a billion stars, offering a comprehensive map of our galaxy. Complementing this, spectroscopic data from surveys such as APOGEE, GALAH, GES, and others provide us with stellar parameters, chemical abundances, ages and velocities. These are vital for understanding the mutual interconnection between different Galactic components. In this talk, I aim to demonstrate what we have learned about the Milky Way using the synergy between large observational data sets, various modeling techniques and state-of-the-art galaxy formation simulations. This integrated approach has led to an in-depth understanding of the disc mass assembly history, the impact of the bar and spiral arms, the formation and present-day structure of the bulge, and the build-up of the Milky Way's stellar halo. Finally, I will discuss how our detailed knowledge about the Milky Way can be used to fill the gaps in our picture of galactic evolution in general. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr Khoperskov will be available for meetings by arrangement with his host Dr Guiglion Guillaume (guiglion@mpia.de).
2024-06-18
16:30
16:30
An Emerging Consensus on White Dwarf Supernovae
Dr. Robert Fisher (University of Massachusetts/Dartmouth & visiting scientist at Heidelberg Institut fuer Theoretische Studien)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Type Ia supernovae (SNe Ia) are thought to be white dwarf stars composed primarily of carbon and oxygen which undergo explosive nuclear burning. SNe Ia are important across many astrophysical domains, serving as standardizable candles for cosmology, sources of cosmic rays, turbulence, and enriched isotopes for the interstellar medium, and endpoints of binary evolution. An isolated white dwarf is inherently stable. Therefore, virtually all explanations for the SN Ia explosion invoke accretion from (or collision with) a companion star. However, the nature of the companion star and the explosion mechanism has remained unclear. The most frequently discussed possibilities are the explosion of a near-Chandrasekhar mass white dwarf accreting from a non-degenerate companion in the single-degenerate channel, or another white dwarf in the double-degenerate channel. I will discuss how a consensus picture for the outcome of these two channels is slowly beginning to emerge, based upon decades of effort from observers and theorists. A new generation of observations from JWST, Nancy Roman, and XRISM will test this picture, both in the observations of UVOIR SNe Ia transients and in the X-ray in their galactic remnants. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr. Robert Fisher (University of Massachusetts/Dartmouth & visiting scientist at Heidelberg Institut fuer Theoretische Studien)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Type Ia supernovae (SNe Ia) are thought to be white dwarf stars composed primarily of carbon and oxygen which undergo explosive nuclear burning. SNe Ia are important across many astrophysical domains, serving as standardizable candles for cosmology, sources of cosmic rays, turbulence, and enriched isotopes for the interstellar medium, and endpoints of binary evolution. An isolated white dwarf is inherently stable. Therefore, virtually all explanations for the SN Ia explosion invoke accretion from (or collision with) a companion star. However, the nature of the companion star and the explosion mechanism has remained unclear. The most frequently discussed possibilities are the explosion of a near-Chandrasekhar mass white dwarf accreting from a non-degenerate companion in the single-degenerate channel, or another white dwarf in the double-degenerate channel. I will discuss how a consensus picture for the outcome of these two channels is slowly beginning to emerge, based upon decades of effort from observers and theorists. A new generation of observations from JWST, Nancy Roman, and XRISM will test this picture, both in the observations of UVOIR SNe Ia transients and in the X-ray in their galactic remnants. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2024-06-11
16:30
16:30
Title to be announced
Professor Leah Morabito (University of Durham)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Abstract to be announced. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor Morabito will be available for meetings by arrangement with her host Dr Eduardo Banados (banados@mpia.de).
Professor Leah Morabito (University of Durham)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Abstract to be announced. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor Morabito will be available for meetings by arrangement with her host Dr Eduardo Banados (banados@mpia.de).
2024-06-11
16:30
16:30
Radiation from shocked plasma around single and binary massive stars
Dr Jonathan Mackey (Dubin Institute for Advanced Studies)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Strong winds from massive stars generate shockwaves in the interstellar medium (ISM) and in wind-wind interactions in binary systems. The shocked plasma is often bright enough to detect from radio to gamma-rays, from which we may gain insights into stellar winds, thermal and non-thermal radiation mechanisms, hydrodynamic instabilities, particle acceleration, and stellar feedback to the ISM. I will show some results on emission from parsec-scale bow shocks driven by massive stars such as Zeta Ophiuchi and BD+43 3654, especially focussing on the boundary layer where wind and ISM are dynamically mixed. Colliding winds in binary systems also produce two-shock structures, but on AU scales with consequently more intense radiation. Surprisingly, we found that inverse-Compton (IC) cooling of the thermal plasma can play a key role in thermodynamics and dynamical stability of the shocked gas. I show results applied to the archetypal colliding-wind binary WR140 in the Cygnus region, for which IC cooling can explain a strong dip in the X-ray lightcurve around periastron. I will show some ongoing work studying the magnetic field configuration in colliding winds, and its dynamical impact. Finally I will discuss our work in the multi-wavelength context of binaries and star clusters, where very interesting advances are being made through gamma-ray observations and modelling. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr Mackey will be available for meetings by arrangement with his host Dr Andreas Sander (andreas.sander@uni-heidelberg.de).
Dr Jonathan Mackey (Dubin Institute for Advanced Studies)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Strong winds from massive stars generate shockwaves in the interstellar medium (ISM) and in wind-wind interactions in binary systems. The shocked plasma is often bright enough to detect from radio to gamma-rays, from which we may gain insights into stellar winds, thermal and non-thermal radiation mechanisms, hydrodynamic instabilities, particle acceleration, and stellar feedback to the ISM. I will show some results on emission from parsec-scale bow shocks driven by massive stars such as Zeta Ophiuchi and BD+43 3654, especially focussing on the boundary layer where wind and ISM are dynamically mixed. Colliding winds in binary systems also produce two-shock structures, but on AU scales with consequently more intense radiation. Surprisingly, we found that inverse-Compton (IC) cooling of the thermal plasma can play a key role in thermodynamics and dynamical stability of the shocked gas. I show results applied to the archetypal colliding-wind binary WR140 in the Cygnus region, for which IC cooling can explain a strong dip in the X-ray lightcurve around periastron. I will show some ongoing work studying the magnetic field configuration in colliding winds, and its dynamical impact. Finally I will discuss our work in the multi-wavelength context of binaries and star clusters, where very interesting advances are being made through gamma-ray observations and modelling. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Dr Mackey will be available for meetings by arrangement with his host Dr Andreas Sander (andreas.sander@uni-heidelberg.de).
2024-05-28
16:30
16:30
Finding the Oldest Star
Professor Alexander Heger (School of Physics and Astronomy, Monash University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The first stars mark the transition from the cosmic dark ages to the modern universe that we know today, a universe that is filled with stars, galaxies, and heavy elements essential to life. The first stars stand out because of their pristine primordial initial composition and their pre-galactic formation environment. Their unique composition dramatically alter their evolution, their structure, the way they die as supernovae, and their resulting nucleosynthesis. The special circumstances under which these stars were formed also impacts their characteristic initial mass distribution, the initial mass function. Generally, it is assumed that these stars typically were significantly more massive than present-day stars. No low-mass Population III star that could have survived to the present day has ever been found. I will give an overview of the evolution and death of these first stars and their supernova. I will discuss nucleosynthesis signatures as possible diagnostics we may use at the present day to learn about these first stars, and where to find these patterns --- with the interesting perspective of potentially identifying the oldest stars in our Milky Way, which may not be the most metal-poor. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Heger will be available for meetings by arrangement with his hosts, Friedrich Roepke (friedrich.roepke@h-its.org) and Andreas Sander (andreas.sander@uni-heidelberg.de)
Professor Alexander Heger (School of Physics and Astronomy, Monash University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
The first stars mark the transition from the cosmic dark ages to the modern universe that we know today, a universe that is filled with stars, galaxies, and heavy elements essential to life. The first stars stand out because of their pristine primordial initial composition and their pre-galactic formation environment. Their unique composition dramatically alter their evolution, their structure, the way they die as supernovae, and their resulting nucleosynthesis. The special circumstances under which these stars were formed also impacts their characteristic initial mass distribution, the initial mass function. Generally, it is assumed that these stars typically were significantly more massive than present-day stars. No low-mass Population III star that could have survived to the present day has ever been found. I will give an overview of the evolution and death of these first stars and their supernova. I will discuss nucleosynthesis signatures as possible diagnostics we may use at the present day to learn about these first stars, and where to find these patterns --- with the interesting perspective of potentially identifying the oldest stars in our Milky Way, which may not be the most metal-poor. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Heger will be available for meetings by arrangement with his hosts, Friedrich Roepke (friedrich.roepke@h-its.org) and Andreas Sander (andreas.sander@uni-heidelberg.de)
2024-05-21
16:30
16:30
Interchange magnetic reconnection as the driver of the fast solar wind
Professor James Drake (Institute for Physical Science and Technology, University of Maryland)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The mechanism that drives the solar wind has been a topic of extensive scientific debate since the 1960's when the existence of the solar wind was confirmed with spacecraft observations. In its recent closest approaches to the sun the Parker Solar Probe (PSP) spacecraft is revealing wind structure not seen by spacecraft at 1AU. The bursty radial flows and associated local reversals of the radial magnetic field (switchbacks) exhibit a spatial periodicity that is linked to that of network magnetic field near the solar surface (Bale et al. 2021; ApJ 923,174). The observations point to magnetic reconnection between open and closed magnetic flux in coronal holes (interchange reconnection) as the driver of these bursts. The corresponding enhancements in plasma pressure, wind speed, and energetic ions further suggest that interchange reconnection is the fundamental source of energy that drives the fast solar wind. We use the PSP data along with the basic characteristics of reconnection to deduce the local properties of interchange reconnection near the solar surface, including the characteristic strength of the reconnecting magnetic, the ambient density, the rate of reconnection and associated rate of energy release (Bale et al. 2023; Nature, vol. 628). An important conclusion of the analysis is that coronal interchange reconnection is in the collisionless regime and that the energy released by interchange reconnection is sufficient to drive the wind. Analytical estimates are supported by particle-in-cell simulations of interchange reconnection that establish that the structure of reconnection exhausts match PSP measurements. The spectra of energetic protons and alpha particles from the simulations, which take the form of powerlaws at high energy, also match the observations by the PSP. The bursty nature of interchange reconnection has implications for the development of the measured turbulence in the solar wind, which is currently being explored. These results have significant implications for understanding the winds produced by objects throughout the universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Drake will be available for meetings by arrangement with his host, Brian Reville (brian.reville@mpi-hd.mpg.de)
Professor James Drake (Institute for Physical Science and Technology, University of Maryland)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The mechanism that drives the solar wind has been a topic of extensive scientific debate since the 1960's when the existence of the solar wind was confirmed with spacecraft observations. In its recent closest approaches to the sun the Parker Solar Probe (PSP) spacecraft is revealing wind structure not seen by spacecraft at 1AU. The bursty radial flows and associated local reversals of the radial magnetic field (switchbacks) exhibit a spatial periodicity that is linked to that of network magnetic field near the solar surface (Bale et al. 2021; ApJ 923,174). The observations point to magnetic reconnection between open and closed magnetic flux in coronal holes (interchange reconnection) as the driver of these bursts. The corresponding enhancements in plasma pressure, wind speed, and energetic ions further suggest that interchange reconnection is the fundamental source of energy that drives the fast solar wind. We use the PSP data along with the basic characteristics of reconnection to deduce the local properties of interchange reconnection near the solar surface, including the characteristic strength of the reconnecting magnetic, the ambient density, the rate of reconnection and associated rate of energy release (Bale et al. 2023; Nature, vol. 628). An important conclusion of the analysis is that coronal interchange reconnection is in the collisionless regime and that the energy released by interchange reconnection is sufficient to drive the wind. Analytical estimates are supported by particle-in-cell simulations of interchange reconnection that establish that the structure of reconnection exhausts match PSP measurements. The spectra of energetic protons and alpha particles from the simulations, which take the form of powerlaws at high energy, also match the observations by the PSP. The bursty nature of interchange reconnection has implications for the development of the measured turbulence in the solar wind, which is currently being explored. These results have significant implications for understanding the winds produced by objects throughout the universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Drake will be available for meetings by arrangement with his host, Brian Reville (brian.reville@mpi-hd.mpg.de)
2024-05-14
16:30
16:30
Cosmology with Galaxy Clusters
Professor Anja von der Linden (Stony Brook University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The observed number of galaxy clusters provides a sensitive probe of the structure of the Universe by measuring the evolution of the halo mass function. However, already current cluster surveys are systematically limited by uncertainties in the relation between cluster mass and observables (e.g. the number of galaxies, X-ray luminosity, or the imprint on the Cosmic Microwave Background). I will discuss the challenges in determining mass-observable relations, and how the combination of multi-wavelength observations, including weak gravitational lensing, can address these. I will summarize current cluster cosmology results for the different selection techniques, including some of the tightest constraints on the dark energy equation of state from a single probe, and will comment on the role of projection effects for optically selected cluster samples. I will conclude with an outlook towards cluster cosmology with upcoming sky surveys, especially with Rubin/LSST. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor von Der Linden will be available for meetings by arrangement with her host, Joachim Wambsganss (jkw@ari.uni-heidelberg.de).
Professor Anja von der Linden (Stony Brook University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The observed number of galaxy clusters provides a sensitive probe of the structure of the Universe by measuring the evolution of the halo mass function. However, already current cluster surveys are systematically limited by uncertainties in the relation between cluster mass and observables (e.g. the number of galaxies, X-ray luminosity, or the imprint on the Cosmic Microwave Background). I will discuss the challenges in determining mass-observable relations, and how the combination of multi-wavelength observations, including weak gravitational lensing, can address these. I will summarize current cluster cosmology results for the different selection techniques, including some of the tightest constraints on the dark energy equation of state from a single probe, and will comment on the role of projection effects for optically selected cluster samples. I will conclude with an outlook towards cluster cosmology with upcoming sky surveys, especially with Rubin/LSST. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor von Der Linden will be available for meetings by arrangement with her host, Joachim Wambsganss (jkw@ari.uni-heidelberg.de).
2024-05-07
16:30
16:30
Deciphering the properties and impact of hot and massive stars with detailed stellar atmosphere modelling
Dr Andreas Sander (Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Massive stars are astrophysical keystones, shaping our cosmic history. As the progenitors of neutron stars and black holes, massive stars reach all nuclear burning stages and - before eventually collapsing - greatly enrich their surrounding medium with momentum, matter, and ionizing radiation. This feedback of massive stars is a building block for the evolution of galaxies, initiating and inhibiting further star formation. In the "afterlives" of massive stars, black holes and neutron stars can merge with each other, giving rise a to Gravitational Wave events. Yet, the overall picture of massive stars we draw in textbooks is rather sketchy and new observational frontiers such as the strong metal-enrichment in high-redshift galaxies discovered by JWST or the black hole statistics obtained from Gravitational Waves only add further pieces to the engmatic massive star puzzle. For a better understanding of massive stars, it is essential to properly determine their parameters and feedback. For young and hot massive stars, many properties are only accessible via spectroscopy. Their quantitative measurements and predictions rely on suitable models for stellar atmospheres, which requires sophisticated simulations to account for their non-equilibrium conditions and strong stellar winds. In this talk, I will introduce the techniques and challenges of atmosphere modelling for hot, massive stars and their winds. Afterwards, I will present a selection of the research efforts within my group demonstrating the range of empirical and theoretical applications of modern non-LTE stellar atmosphere models, such as the analysis of important landmarks of massive star evolution, the search for "hidden" post-interaction binaries, or theoretical insights on radiation-driven winds. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Andreas Sander (Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Massive stars are astrophysical keystones, shaping our cosmic history. As the progenitors of neutron stars and black holes, massive stars reach all nuclear burning stages and - before eventually collapsing - greatly enrich their surrounding medium with momentum, matter, and ionizing radiation. This feedback of massive stars is a building block for the evolution of galaxies, initiating and inhibiting further star formation. In the "afterlives" of massive stars, black holes and neutron stars can merge with each other, giving rise a to Gravitational Wave events. Yet, the overall picture of massive stars we draw in textbooks is rather sketchy and new observational frontiers such as the strong metal-enrichment in high-redshift galaxies discovered by JWST or the black hole statistics obtained from Gravitational Waves only add further pieces to the engmatic massive star puzzle. For a better understanding of massive stars, it is essential to properly determine their parameters and feedback. For young and hot massive stars, many properties are only accessible via spectroscopy. Their quantitative measurements and predictions rely on suitable models for stellar atmospheres, which requires sophisticated simulations to account for their non-equilibrium conditions and strong stellar winds. In this talk, I will introduce the techniques and challenges of atmosphere modelling for hot, massive stars and their winds. Afterwards, I will present a selection of the research efforts within my group demonstrating the range of empirical and theoretical applications of modern non-LTE stellar atmosphere models, such as the analysis of important landmarks of massive star evolution, the search for "hidden" post-interaction binaries, or theoretical insights on radiation-driven winds. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2024-04-30
16:30
16:30
Rim Worlds: Computational astrophysics of accretion disks
Dr Mario Flock (Max-Planck-Institut fuer Astronomie)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Understanding the formation of (exo)-planetary systems requires the combined effort of advanced computational models and high-resolution multi-wavelength observations. In my talk, I will review our current understanding of the dynamic evolution of protoplanetary disks. 3D multi-physics simulations and high-performance computing allow us to study the thermal and kinematical evolution of young circumstellar disks and planets' birthplaces in detail. I will also highlight why the inner disk regions, especially those close to the silicate sublimation, are crucial for forming terrestrial planets. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Mario Flock (Max-Planck-Institut fuer Astronomie)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Understanding the formation of (exo)-planetary systems requires the combined effort of advanced computational models and high-resolution multi-wavelength observations. In my talk, I will review our current understanding of the dynamic evolution of protoplanetary disks. 3D multi-physics simulations and high-performance computing allow us to study the thermal and kinematical evolution of young circumstellar disks and planets' birthplaces in detail. I will also highlight why the inner disk regions, especially those close to the silicate sublimation, are crucial for forming terrestrial planets. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2024-04-23
16:30
16:30
The Gaia mission: an exceptional astrometric, photometric and spectroscopic multi-epoch survey
Dr. Laurent Eyer (Observatoire de Geneve)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Grand Lecture Room
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Abstract
At the core of the ESA Gaia mission lies a comprehensive multi-epoch survey, with astrometric, photometric, spectrophotometric, and spectroscopic measurements of the entire sky. The astrometric time series provide parallax and proper motion, also impacting astrometric binary stars, and the detection of black holes and exoplanets. The photometric measurements allow us to describe the star properties and their variability in an unprecedented manner, leading to many records and impacting the distance scale. The radial velocity breaks also observational records and allows us to improve and complete the description of binaries and kinematic properties of the Milky Way. The breadth of the results of Gaia is so wide that it is nearly impossible to summarize all its aspects. I will give a review of (biased) selected topics. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Eyer will be available for meetings by arrangement with his hosts, Saskia Hekker (saskia.hekker@h-its.org) and Michael Bazot (michael.bazot@h-its.org)
Dr. Laurent Eyer (Observatoire de Geneve)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Grand Lecture Room
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Abstract
At the core of the ESA Gaia mission lies a comprehensive multi-epoch survey, with astrometric, photometric, spectrophotometric, and spectroscopic measurements of the entire sky. The astrometric time series provide parallax and proper motion, also impacting astrometric binary stars, and the detection of black holes and exoplanets. The photometric measurements allow us to describe the star properties and their variability in an unprecedented manner, leading to many records and impacting the distance scale. The radial velocity breaks also observational records and allows us to improve and complete the description of binaries and kinematic properties of the Milky Way. The breadth of the results of Gaia is so wide that it is nearly impossible to summarize all its aspects. I will give a review of (biased) selected topics. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Eyer will be available for meetings by arrangement with his hosts, Saskia Hekker (saskia.hekker@h-its.org) and Michael Bazot (michael.bazot@h-its.org)
2024-02-06
16:30
16:30
The colourful past and dark side of galaxies unveiled through population-dynamics of their stars
Professor van de Ven (University of Vienna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Driven by gravity, galaxies continuously grow through accretion of smaller systems. Stellar streams are nice illustrations of this hierarchical build-up, but the accreted stars quickly disperse. I will present advanced dynamical models that can convert the observed positions and velocities of stars to phase-space quantities like energy and angular momentum which remain largely conserved. In addition, these models can include the observed ages and chemical properties of stars which are also conserved. The resulting population-dynamical models allow us then to uncover even those accretion events which are now fully dispersed. At the same time, these models also accurately constrain the total mass distribution, including a central black hole and dark matter halo. I will illustrate how these models make optimally use of observations to unveil the dark side and colour past of galaxies: from accurate measurements of their central black holes and extended dark halos, to unveiling the formation history of their disks, to uncovering ancient massive mergers and accreted satellite galaxies. By the end, I aim to have demonstrated that these models provide a unique bridge between the studies of resolved stars in the Milky Way and integrated-light of high(er)-redshift galaxies. Together with direct coupling to state-of-the-art galaxy formation simulations, these population-dynamical models enable us to uncover the hierarchical build-up of galaxies in a cosmological context. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor van de Ven will be available for meetings by arrangement with his host, Nadine Neumayer (neumayer@mpia.de)
Professor van de Ven (University of Vienna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Driven by gravity, galaxies continuously grow through accretion of smaller systems. Stellar streams are nice illustrations of this hierarchical build-up, but the accreted stars quickly disperse. I will present advanced dynamical models that can convert the observed positions and velocities of stars to phase-space quantities like energy and angular momentum which remain largely conserved. In addition, these models can include the observed ages and chemical properties of stars which are also conserved. The resulting population-dynamical models allow us then to uncover even those accretion events which are now fully dispersed. At the same time, these models also accurately constrain the total mass distribution, including a central black hole and dark matter halo. I will illustrate how these models make optimally use of observations to unveil the dark side and colour past of galaxies: from accurate measurements of their central black holes and extended dark halos, to unveiling the formation history of their disks, to uncovering ancient massive mergers and accreted satellite galaxies. By the end, I aim to have demonstrated that these models provide a unique bridge between the studies of resolved stars in the Milky Way and integrated-light of high(er)-redshift galaxies. Together with direct coupling to state-of-the-art galaxy formation simulations, these population-dynamical models enable us to uncover the hierarchical build-up of galaxies in a cosmological context. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor van de Ven will be available for meetings by arrangement with his host, Nadine Neumayer (neumayer@mpia.de)
2024-01-30
16:30
16:30
Galactic Archaeology, Near and (Sort of) Far
Professor Gail Zasowski (University of Utah)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Understanding galaxies and their evolution over time is critical for interpreting the stellar history and chemical enrichment of the Universe. Galaxies that lie at different distances help us fill in different pieces of the puzzle — from large statistical samples of coarsely-resolved systems to our own Milky Way, which gives us a unique, up-close picture of galaxy structure and fundamental stellar physics. I will describe the Milky Way and Local Group in the context of galactic studies and highlight recent work that explores how stars and gas shape the evolution of galaxies on a wide variety of scales. With numerous new surveys in progress and on the horizon, including Gaia, the next generation of SDSS, and the Roman Space Telescope, these topics promise to be exciting avenues of research for many years to come. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor Zasowski will be available for meetings by arrangement with her host, Dominika Wylezalek (wylezalek@uni-heidelberg.de)
Professor Gail Zasowski (University of Utah)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Understanding galaxies and their evolution over time is critical for interpreting the stellar history and chemical enrichment of the Universe. Galaxies that lie at different distances help us fill in different pieces of the puzzle — from large statistical samples of coarsely-resolved systems to our own Milky Way, which gives us a unique, up-close picture of galaxy structure and fundamental stellar physics. I will describe the Milky Way and Local Group in the context of galactic studies and highlight recent work that explores how stars and gas shape the evolution of galaxies on a wide variety of scales. With numerous new surveys in progress and on the horizon, including Gaia, the next generation of SDSS, and the Roman Space Telescope, these topics promise to be exciting avenues of research for many years to come. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg, Professor Zasowski will be available for meetings by arrangement with her host, Dominika Wylezalek (wylezalek@uni-heidelberg.de)
2024-01-23
16:30
16:30
Unveiling Dust Beyond the Local Universe
Dr Irene Shivaei (Centro de Astrobiología (CAB), Madrid)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
At the core of galaxy evolution is the evolution of the baryonic components that modify the observable properties of galaxies. A crucial component of baryonic matter is the interstellar medium (ISM) that consists of gas and solid-phase metals called dust. Interstellar dust determines how galaxies look like from UV to sub-mm, how the ISM behaves, and the very process of star formation that creates the stellar component that defines a galaxy. We are now at the beginning of an exciting journey with the unprecedented infrared capabilities, high sensitivity, and high angular resolution of JWST/MIRI compared to its predecessors such as Spitzer. For the first time, we are able to not only detect warm dust emission in individual typical galaxies across masses and star formation rates (SFRs) at cosmic noon, but also resolve the dust-obscured SFR in more extended sources at z~1. In this talk, I will show the recent results of my research on a panchromatic study of dust emission and absorption properties of galaxies at cosmic noon and review the new results from our multi-band MIRI survey, SMILES, covering 5 to 25um wavelength in HUDF. This extensive survey focuses on obscured AGN and star formation within cosmic noon galaxies, extending our reach to galaxies with stellar masses an order of magnitude lower than ever observed before. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg Dr Shivaei will be available for meetings by arrangement with her host, Leindert Boogaard (boogaard@mpia.de)
Dr Irene Shivaei (Centro de Astrobiología (CAB), Madrid)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
At the core of galaxy evolution is the evolution of the baryonic components that modify the observable properties of galaxies. A crucial component of baryonic matter is the interstellar medium (ISM) that consists of gas and solid-phase metals called dust. Interstellar dust determines how galaxies look like from UV to sub-mm, how the ISM behaves, and the very process of star formation that creates the stellar component that defines a galaxy. We are now at the beginning of an exciting journey with the unprecedented infrared capabilities, high sensitivity, and high angular resolution of JWST/MIRI compared to its predecessors such as Spitzer. For the first time, we are able to not only detect warm dust emission in individual typical galaxies across masses and star formation rates (SFRs) at cosmic noon, but also resolve the dust-obscured SFR in more extended sources at z~1. In this talk, I will show the recent results of my research on a panchromatic study of dust emission and absorption properties of galaxies at cosmic noon and review the new results from our multi-band MIRI survey, SMILES, covering 5 to 25um wavelength in HUDF. This extensive survey focuses on obscured AGN and star formation within cosmic noon galaxies, extending our reach to galaxies with stellar masses an order of magnitude lower than ever observed before. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During her visit to Heidelberg Dr Shivaei will be available for meetings by arrangement with her host, Leindert Boogaard (boogaard@mpia.de)
2024-01-16
16:30
16:30
Machine learning you can trust for cosmology and astrophysics
Professor Roberto Trotta (SISSA, Trieste, Imperial College London)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Cosmological and astrophysical data are now sufficiently large and complex to become almost intractable by traditional statistical techniques. Unravelling the twin mysteries of dark energy and dark matter will require new data analysis methods capable of extracting knowledge from upcoming data streams, including the Euclid satellite, the Nancy Grace Roman space telescope, LSST/Vera Rubin observatory and LISA. While machine learning offers great promise, it suffers from difficulties in interpretability as well as from poor generalisation when the training set is not representative of the target data (known as “covariate shift”) - an almost ubiquitous problem in astronomy due to selection effects. I will motivate and present some of the latest machine learning tools being developed for fast and scalable inference, focusing on simulation based inference and particularly on neural ratio estimation for amortised marginal posterior inference as the natural heir to classical Bayesian inference techniques. I will then discuss a general, statistically principled solution to covariate shift in supervised learning, which achieves gold standard performance in a variety of important test cases. I will conclude with example applications in supernova type Ia cosmology, dark matter direct detection and gravitational waves astronomy. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg Professor Trotta will be available for meetings by arrangement with his host, Ivelina Momcheva (momcheva@mpia.de).
Professor Roberto Trotta (SISSA, Trieste, Imperial College London)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Cosmological and astrophysical data are now sufficiently large and complex to become almost intractable by traditional statistical techniques. Unravelling the twin mysteries of dark energy and dark matter will require new data analysis methods capable of extracting knowledge from upcoming data streams, including the Euclid satellite, the Nancy Grace Roman space telescope, LSST/Vera Rubin observatory and LISA. While machine learning offers great promise, it suffers from difficulties in interpretability as well as from poor generalisation when the training set is not representative of the target data (known as “covariate shift”) - an almost ubiquitous problem in astronomy due to selection effects. I will motivate and present some of the latest machine learning tools being developed for fast and scalable inference, focusing on simulation based inference and particularly on neural ratio estimation for amortised marginal posterior inference as the natural heir to classical Bayesian inference techniques. I will then discuss a general, statistically principled solution to covariate shift in supervised learning, which achieves gold standard performance in a variety of important test cases. I will conclude with example applications in supernova type Ia cosmology, dark matter direct detection and gravitational waves astronomy. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg Professor Trotta will be available for meetings by arrangement with his host, Ivelina Momcheva (momcheva@mpia.de).
2024-01-09
16:30
16:30
Black holes in binaries
Professor Ilya Mandel (Monash University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Recent observational successes are providing a new impetus to the study of binaries containing stellar-mass black holes. I will start with a very brief review of the current understanding of massive binary evolution leading to the formation of black-hole binaries. I will then focus on a few of the outstanding issues in interpreting both X-ray and gravitational-wave observations and propose pathways for improving our understanding of some challenging aspects of binary evolution. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Mandel will be available for meetings by arrangement with his hosts, Friedrich Roepke (roepke@uni-heidelberg.de) and Fabian Schneider (fabian.schneider@h-its.org)
Professor Ilya Mandel (Monash University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Recent observational successes are providing a new impetus to the study of binaries containing stellar-mass black holes. I will start with a very brief review of the current understanding of massive binary evolution leading to the formation of black-hole binaries. I will then focus on a few of the outstanding issues in interpreting both X-ray and gravitational-wave observations and propose pathways for improving our understanding of some challenging aspects of binary evolution. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Mandel will be available for meetings by arrangement with his hosts, Friedrich Roepke (roepke@uni-heidelberg.de) and Fabian Schneider (fabian.schneider@h-its.org)
2023-12-12
16:30
16:30
The early growth of quasars and their host galaxies
Dr Roberto Decarli (Istituto Nazionale di Astrofisica (INAF), Bologna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Since their first discovery about 60 years ago, quasars have been at the forefront of our understanding of the distant universe. We now know >400 quasars at redshift z>6, when the Universe was < 1 Gyr old. Their mere presence poses a challenge to models of the formation and early growth not only of their massive black holes, but also of their host galaxies, their dust content, and the large-scale structures where they reside. In the last few years, however, we have witnessed transformational leaps in our understanding of the properties of early quasars, thanks to unprecedented observational achievements, in particular with ALMA and JWST. We have now accurate black hole mass estimates in quasars up to z~7.6; we have mapped the gas and dust distribution in the quasar host galaxies down to 100 pc resolution, and quantified their star formation rate, metallicity, and other properties (gas density, photoionization conditions, etc); and we have secured a census of tens of spectroscopically-confirmed galaxies in the environment of quasars at z>6. These observational results allow us to sketch a novel picture on the formation of some of the most massive astrophysical sources in the early Universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Decarli is available for meetings by arrangement with his host, Kathryn Kreckel (kathryn.kreckel@uni-heidelberg.de)
Dr Roberto Decarli (Istituto Nazionale di Astrofisica (INAF), Bologna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Since their first discovery about 60 years ago, quasars have been at the forefront of our understanding of the distant universe. We now know >400 quasars at redshift z>6, when the Universe was < 1 Gyr old. Their mere presence poses a challenge to models of the formation and early growth not only of their massive black holes, but also of their host galaxies, their dust content, and the large-scale structures where they reside. In the last few years, however, we have witnessed transformational leaps in our understanding of the properties of early quasars, thanks to unprecedented observational achievements, in particular with ALMA and JWST. We have now accurate black hole mass estimates in quasars up to z~7.6; we have mapped the gas and dust distribution in the quasar host galaxies down to 100 pc resolution, and quantified their star formation rate, metallicity, and other properties (gas density, photoionization conditions, etc); and we have secured a census of tens of spectroscopically-confirmed galaxies in the environment of quasars at z>6. These observational results allow us to sketch a novel picture on the formation of some of the most massive astrophysical sources in the early Universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Decarli is available for meetings by arrangement with his host, Kathryn Kreckel (kathryn.kreckel@uni-heidelberg.de)
2023-12-05
16:30
16:30
WEAVE: Science, design, commissioning, and survey
Professor Scott Trager (Kapteyn Astronomical Institute, University of Groningen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
WEAVE is the next-generation wide-field survey facility for the William Herschel Telescope (WHT). WEAVE will provide the instrument required for full scientific exploitation of the Gaia, LOFAR, and APERTIF surveys in the Northern Hemisphere. WEAVE is a multi-object and multi-integral-field-unit (IFU) facility utilizing a large, new 2-degree-diameter prime focus corrector at the WHT with a pick-and-place fibre positioner system hosting nearly 1000 multi-object fibres or 20 mini-IFUs for each observation, or a single wide-field IFU. The fibres are fed into a dual-beam spectrograph located in the GHRIL enclosure on the WHT's Nasmyth platform. The spectrograph records nearly 1000 spectra simultaneously at a resolution of R~5000 over an instantaneous wavelength range of 360-950 nm or at a resolution of R~20000 over two more-limited wavelength ranges. WEAVE has been on sky since late 2022. The WEAVE Survey will provide complete phase-space coordinates of roughly 3 million stars in the northern sky selected with ESO’s Gaia satellite, chemical analysis of more than 1 million stars from Gaia, half a million massive stars in the Galactic Plane, distances and properties of galaxies selected from the low-frequency radio-wave surveys being conducted with LOFAR, “three-dimensional" spectroscopy of galaxies selected from surveys using the new Apertif focal plane array at WSRT, and deep surveys of galaxy clusters and moderate-redshift galaxies. In this talk I will discuss the motivation, design, construction, and commissioning of WEAVE and the “first-light”, Science Verification, and early WEAVE Survey data we’ve already collected with it. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Trager is available for meetings by arrangement with his hosts, Kathryn Kreckel (kathryn.kreckel@uni-heidelberg.de) and Cormac Larkin (cormac.larkin@uni-heidelberg.de).
Professor Scott Trager (Kapteyn Astronomical Institute, University of Groningen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
WEAVE is the next-generation wide-field survey facility for the William Herschel Telescope (WHT). WEAVE will provide the instrument required for full scientific exploitation of the Gaia, LOFAR, and APERTIF surveys in the Northern Hemisphere. WEAVE is a multi-object and multi-integral-field-unit (IFU) facility utilizing a large, new 2-degree-diameter prime focus corrector at the WHT with a pick-and-place fibre positioner system hosting nearly 1000 multi-object fibres or 20 mini-IFUs for each observation, or a single wide-field IFU. The fibres are fed into a dual-beam spectrograph located in the GHRIL enclosure on the WHT's Nasmyth platform. The spectrograph records nearly 1000 spectra simultaneously at a resolution of R~5000 over an instantaneous wavelength range of 360-950 nm or at a resolution of R~20000 over two more-limited wavelength ranges. WEAVE has been on sky since late 2022. The WEAVE Survey will provide complete phase-space coordinates of roughly 3 million stars in the northern sky selected with ESO’s Gaia satellite, chemical analysis of more than 1 million stars from Gaia, half a million massive stars in the Galactic Plane, distances and properties of galaxies selected from the low-frequency radio-wave surveys being conducted with LOFAR, “three-dimensional" spectroscopy of galaxies selected from surveys using the new Apertif focal plane array at WSRT, and deep surveys of galaxy clusters and moderate-redshift galaxies. In this talk I will discuss the motivation, design, construction, and commissioning of WEAVE and the “first-light”, Science Verification, and early WEAVE Survey data we’ve already collected with it. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Trager is available for meetings by arrangement with his hosts, Kathryn Kreckel (kathryn.kreckel@uni-heidelberg.de) and Cormac Larkin (cormac.larkin@uni-heidelberg.de).
2023-11-28
16:30
16:30
Cracking the Cosmic-ray Conundrum
Dr Brian Reville (Max-Planck-Institut für Kernphysik, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The search for the origins of cosmic rays has been a thorn in the side of high-energy astrophysicists for more than a century. This talk will provide an overview of the current state of understanding regarding the origins of cosmic rays, highlighting some of the outstanding problems and challenges. I will provide some examples of how recent gamma-ray observations are advancing the field, and how the next generation of gamma-ray observatories may crack this long-standing problem Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Brian Reville (Max-Planck-Institut für Kernphysik, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The search for the origins of cosmic rays has been a thorn in the side of high-energy astrophysicists for more than a century. This talk will provide an overview of the current state of understanding regarding the origins of cosmic rays, highlighting some of the outstanding problems and challenges. I will provide some examples of how recent gamma-ray observations are advancing the field, and how the next generation of gamma-ray observatories may crack this long-standing problem Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2023-11-21
16:30
16:30
The different atmospheric regimes that characterise extrasolar planets
Professor Dr. Christiane Helling (Space Research Institut*, Austrian Academy of Science; University of Technology Graz *https://www.oeaw.ac.at/iwf/)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
JWST observations reveal snapshot insights into exoplanet atmospheres confirming often for the first time the presence of chemically rich environments. For most exoplanets, cloud particles form that affect their atmospheric environments by multiple feedback processes. The physical understanding of such observations therefore requires comprehensive modelling approaches that combine 3D radiation-hydrodynamic simulations with appropriately complex gas phase and cloud formation models. I will therefore present: 1) Our recent advances in detailed, kinetic cloud formation modelling where we utilise quantum-chemical simulations and laboratory experiments to support our model building, and 2) how we utilise 3D global simulations to define atmospheric regimes that help to characterise exoplanets in different planetary system configurations. Lastly, I plan on discussing the potential of polarimetry as well as future space missions like PLATO to strengthen the impact of the JWST observational efforts. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Helling is available for meetings by arrangement with her host, Hans Ludwig (H.Ludwig@lsw.uni-heidelberg.de).
Professor Dr. Christiane Helling (Space Research Institut*, Austrian Academy of Science; University of Technology Graz *https://www.oeaw.ac.at/iwf/)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
JWST observations reveal snapshot insights into exoplanet atmospheres confirming often for the first time the presence of chemically rich environments. For most exoplanets, cloud particles form that affect their atmospheric environments by multiple feedback processes. The physical understanding of such observations therefore requires comprehensive modelling approaches that combine 3D radiation-hydrodynamic simulations with appropriately complex gas phase and cloud formation models. I will therefore present: 1) Our recent advances in detailed, kinetic cloud formation modelling where we utilise quantum-chemical simulations and laboratory experiments to support our model building, and 2) how we utilise 3D global simulations to define atmospheric regimes that help to characterise exoplanets in different planetary system configurations. Lastly, I plan on discussing the potential of polarimetry as well as future space missions like PLATO to strengthen the impact of the JWST observational efforts. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Helling is available for meetings by arrangement with her host, Hans Ludwig (H.Ludwig@lsw.uni-heidelberg.de).
2023-11-14
16:30
16:30
How Stars End their Lives
Professor Phillip Podsiadlowski (University of Oxford & HITS (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Over the last few decades a broad picture has been established of how stars of different masses end the lives: low- and intermediate-mass stars lose a large fraction of their initial mass and become white dwarfs, possibly connected with the formation of a planetary nebula; massive stars either produce neutron stars or black holes, mostly, but not always associated with a supernova explosion; and the most massive stars may even disrupt themselves completely. I will first discuss the basic theoretical framework to understand these different fates and some of the empirical, observational evidence supporting it. I will then discuss some key fundamental questions that are not properly understood to date, specifically what causes the extreme mass loss of low- and intermediate-mass stars that ultimately terminates their evolution, and what determines the core collapse fate of massive stars, both areas in which there has been dramatic progress in recent year. I will also show how gravitational-wave observations with LIGO can be used to test some of these predictions in the very near future. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Podsiadlowski is available for meetings by arrangement with his hosts, Friedrich Roepke (roepke@uni-heidelberg.de) and Fabian Schneider (fabian.schneider@h-its.org).
Professor Phillip Podsiadlowski (University of Oxford & HITS (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Over the last few decades a broad picture has been established of how stars of different masses end the lives: low- and intermediate-mass stars lose a large fraction of their initial mass and become white dwarfs, possibly connected with the formation of a planetary nebula; massive stars either produce neutron stars or black holes, mostly, but not always associated with a supernova explosion; and the most massive stars may even disrupt themselves completely. I will first discuss the basic theoretical framework to understand these different fates and some of the empirical, observational evidence supporting it. I will then discuss some key fundamental questions that are not properly understood to date, specifically what causes the extreme mass loss of low- and intermediate-mass stars that ultimately terminates their evolution, and what determines the core collapse fate of massive stars, both areas in which there has been dramatic progress in recent year. I will also show how gravitational-wave observations with LIGO can be used to test some of these predictions in the very near future. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Podsiadlowski is available for meetings by arrangement with his hosts, Friedrich Roepke (roepke@uni-heidelberg.de) and Fabian Schneider (fabian.schneider@h-its.org).
2023-11-07
16:30
16:30
Dynamos: magnetic fields almost everywhere in astrophysics
Professor Axel Brandenburg (Nordita, Stockholm)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
Long ago, magnetic fields used to be something for specialists and not necessarily for the ordinary astrophysicist. This has drastically changed over the past few decades. Nowadays, many people invoke the magnetorotational instability to explain turbulence and growth or at least the maintenance of magnetic fields in accretion disks or in core-collapse supernovae, for example. Star formation is another example where magnetic fields are crucial to making the gas collapse. Yet another example is stellar activity, where the presence of magnetic fields makes all the difference compared to just a radially symmetric solution to the stellar structure equations. Magnetic fields may even play a role in solving the Hubble tension, the difference between the measured values of 73 km/s/Mpc for the late Universe and 67.7 km/s/Mpc for the early Universe. In my talk, I will start with a historical perspective, going back to the days when the existence and origin of magnetic fields was still very obscure. We knew about the Earth's magnetic field since the 1600s, and astronomical observations have revealed magnetic fields in sunspots and eventually in other stars and galaxies during the last century. To understand their origin, people had to struggle with Cowling's anti-dynamo theorem that magnetic fields cannot be generated from kinetic energy in a simple axisymmetric geometry. Gradually, it became clear that in three-dimensional settings, self-excited dynamos do actually work. see the figure showing magnetic field vectors in orange and yellow, compared to vorticity vectors in white near a low-pressure tube in blue. Meanwhile, with the emergence of three-dimensional simulations, where the plasma motions tend to be turbulent, it becomes hard to think of any situation were magnetic fields would not exist! Dynamo action has now also been realized in the lab in various configurations. But some basic questions are still troubling us: why exactly is the Sun's magnetic field exhibiting equatorward migration and why do simulations not yet reproduce the large-scale magnetic fields observed in spiral galaxies. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Brandenburg is available for meetings by arrangement with his host, Friedrich Roepke (roepke@uni-heidelberg.de)
Professor Axel Brandenburg (Nordita, Stockholm)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
Long ago, magnetic fields used to be something for specialists and not necessarily for the ordinary astrophysicist. This has drastically changed over the past few decades. Nowadays, many people invoke the magnetorotational instability to explain turbulence and growth or at least the maintenance of magnetic fields in accretion disks or in core-collapse supernovae, for example. Star formation is another example where magnetic fields are crucial to making the gas collapse. Yet another example is stellar activity, where the presence of magnetic fields makes all the difference compared to just a radially symmetric solution to the stellar structure equations. Magnetic fields may even play a role in solving the Hubble tension, the difference between the measured values of 73 km/s/Mpc for the late Universe and 67.7 km/s/Mpc for the early Universe. In my talk, I will start with a historical perspective, going back to the days when the existence and origin of magnetic fields was still very obscure. We knew about the Earth's magnetic field since the 1600s, and astronomical observations have revealed magnetic fields in sunspots and eventually in other stars and galaxies during the last century. To understand their origin, people had to struggle with Cowling's anti-dynamo theorem that magnetic fields cannot be generated from kinetic energy in a simple axisymmetric geometry. Gradually, it became clear that in three-dimensional settings, self-excited dynamos do actually work. see the figure showing magnetic field vectors in orange and yellow, compared to vorticity vectors in white near a low-pressure tube in blue. Meanwhile, with the emergence of three-dimensional simulations, where the plasma motions tend to be turbulent, it becomes hard to think of any situation were magnetic fields would not exist! Dynamo action has now also been realized in the lab in various configurations. But some basic questions are still troubling us: why exactly is the Sun's magnetic field exhibiting equatorward migration and why do simulations not yet reproduce the large-scale magnetic fields observed in spiral galaxies. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Brandenburg is available for meetings by arrangement with his host, Friedrich Roepke (roepke@uni-heidelberg.de)
2023-10-24
16:30
16:30
The cloud-scale baryon cycle across the nearby galaxy population
Dr Melanie Chevance (Institut für Theoretische Astrophysik, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Galaxies are in constant evolution, under the influence of the matter cycle within them: gas clouds assemble and collapse, stars form within them, and matter and energy are redistributed into the interstellar medium through the influence of stellar feedback and turbulence. However, the exact physical mechanisms driving this complex, multi-scale cycle remain elusive, due to a lack of observational constraints. As a result, it remains one of the big unanswered questions in modern astrophysics which processes drive this matter cycle, from the small-scale dense gas clouds within which stars form, to large-scale, feedback-driven outflows, and what its quantitative characteristics are. By combining an unprecedented variety of in-hand, multi-wavelength observations of a broad range of galactic environments, I will present how we can characterise for the first time the successive steps of the matter cycle, from the assembly of dense gas clouds from the diffuse interstellar medium, to the successive collapse, star formation and dispersal by stellar feedback redistributing matter and energy back into the diffuse medium. I will show that molecular clouds are rapidly destroyed by stellar feedback (within 1-5 Myr), which drastically limit their star formation efficiency to 2 to 10% depending on the galactic environment. Comparison of this rapid destruction time-scale with analytical predictions demonstrates that, independently of the environment, early feedback mechanisms (photoionisation and stellar winds) play a crucial role in dispersing molecular clouds and limiting their star formation efficiency in nearby galaxies. Finally, I will show that the vast majority of momentum and energy emitted by the young stellar populations escapes the parent cloud, affecting galaxies on large scales. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Melanie Chevance (Institut für Theoretische Astrophysik, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Galaxies are in constant evolution, under the influence of the matter cycle within them: gas clouds assemble and collapse, stars form within them, and matter and energy are redistributed into the interstellar medium through the influence of stellar feedback and turbulence. However, the exact physical mechanisms driving this complex, multi-scale cycle remain elusive, due to a lack of observational constraints. As a result, it remains one of the big unanswered questions in modern astrophysics which processes drive this matter cycle, from the small-scale dense gas clouds within which stars form, to large-scale, feedback-driven outflows, and what its quantitative characteristics are. By combining an unprecedented variety of in-hand, multi-wavelength observations of a broad range of galactic environments, I will present how we can characterise for the first time the successive steps of the matter cycle, from the assembly of dense gas clouds from the diffuse interstellar medium, to the successive collapse, star formation and dispersal by stellar feedback redistributing matter and energy back into the diffuse medium. I will show that molecular clouds are rapidly destroyed by stellar feedback (within 1-5 Myr), which drastically limit their star formation efficiency to 2 to 10% depending on the galactic environment. Comparison of this rapid destruction time-scale with analytical predictions demonstrates that, independently of the environment, early feedback mechanisms (photoionisation and stellar winds) play a crucial role in dispersing molecular clouds and limiting their star formation efficiency in nearby galaxies. Finally, I will show that the vast majority of momentum and energy emitted by the young stellar populations escapes the parent cloud, affecting galaxies on large scales. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2023-07-25
16:00
16:00
The most massive stars
Professor Alex de Koter (Anton Pannekoek Institute of Astronomy, Amsterdam, and the Institute for Astronomy, KU Leuven)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Massive stars may have been the first sources of light after the Big Bang. They are potential contributors to the re-ionization of the Universe and have likely played a crucial role in galaxy formation. The most massive stars today easily outshine the sun by a factor of a million or more, hence provide strong radiative feedback on their host environment. Through powerful stellar winds and supernova ejecta they enrich their surroundings with newly processed chemical elements, which constitute the building blocks of terrestrial planets and life. The detection of gravitational waves revealed surprisingly high black hole masses, pointing to very massive progenitor stars in binary systems. So, massive stars are important in many astrophysical contexts. In this mid-summer broad overview talk I will sketch some of the open problems in the formation and evolution of massive stars, and the key physics involved. I will also present and discuss recent results, including findings regarding the mass-loss properties of massive stars -- both as hot main-sequence stars and as cool red supergiants, the maximum formation mass, and the production of runaway massive stars by dynamical ejection from massive young clusters. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor de Koter is available for meetings by arrangement with his host, Maria Ramirez-Tannus (ramirez@mpia.de).
Professor Alex de Koter (Anton Pannekoek Institute of Astronomy, Amsterdam, and the Institute for Astronomy, KU Leuven)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Massive stars may have been the first sources of light after the Big Bang. They are potential contributors to the re-ionization of the Universe and have likely played a crucial role in galaxy formation. The most massive stars today easily outshine the sun by a factor of a million or more, hence provide strong radiative feedback on their host environment. Through powerful stellar winds and supernova ejecta they enrich their surroundings with newly processed chemical elements, which constitute the building blocks of terrestrial planets and life. The detection of gravitational waves revealed surprisingly high black hole masses, pointing to very massive progenitor stars in binary systems. So, massive stars are important in many astrophysical contexts. In this mid-summer broad overview talk I will sketch some of the open problems in the formation and evolution of massive stars, and the key physics involved. I will also present and discuss recent results, including findings regarding the mass-loss properties of massive stars -- both as hot main-sequence stars and as cool red supergiants, the maximum formation mass, and the production of runaway massive stars by dynamical ejection from massive young clusters. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor de Koter is available for meetings by arrangement with his host, Maria Ramirez-Tannus (ramirez@mpia.de).
2023-07-18
16:00
16:00
The hot phase of the interstellar medium
Professor Manami Sasaki (Erlangen Centre for Astroparticle Physics, University of Erlangen-Nuernberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The interstellar medium (ISM) in galaxies is ionised and heated by shock waves caused by stellar winds of massive stars and by supernova explosions. The combination of these effects can create large structures in the ISM called superbubbles, filled with hot, low-density plasma. Supernova remnants (SNRs) also act as recycling centres, which return elements processed in stars to the ISM. In addition, particles are accelerated to relativistic energies in the strong interstellar shocks. The emission from hot plasma is best studied in soft X-rays. I will present studies of SNRs and the hot phase of the ISM in our Galaxy and the nearby galaxies and discuss the physics of hot plasma, the evolution and energetics of SNRs and superbubbles, and their impact on star formation. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Sasaki is available for meetings by arrangement with her hosts, Kathryn Kreckel (Kathryn.Kreckel@uni-heidelberg.de) and Ralf Klessen (klessen@uni-heidelberg.de).
Professor Manami Sasaki (Erlangen Centre for Astroparticle Physics, University of Erlangen-Nuernberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The interstellar medium (ISM) in galaxies is ionised and heated by shock waves caused by stellar winds of massive stars and by supernova explosions. The combination of these effects can create large structures in the ISM called superbubbles, filled with hot, low-density plasma. Supernova remnants (SNRs) also act as recycling centres, which return elements processed in stars to the ISM. In addition, particles are accelerated to relativistic energies in the strong interstellar shocks. The emission from hot plasma is best studied in soft X-rays. I will present studies of SNRs and the hot phase of the ISM in our Galaxy and the nearby galaxies and discuss the physics of hot plasma, the evolution and energetics of SNRs and superbubbles, and their impact on star formation. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Sasaki is available for meetings by arrangement with her hosts, Kathryn Kreckel (Kathryn.Kreckel@uni-heidelberg.de) and Ralf Klessen (klessen@uni-heidelberg.de).
2023-07-04
16:00
16:00
Measuring the positions of the stars: giant strides in understanding the Universe
Professor Michael Perryman (University College Dublin)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Large Lecture Hall (gHS)
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Abstract
The Hipparcos satellite project of the European Space Agency was dedicated to measuring the accurate positions of more than 100,000 stars. Doing so from space represented a fundamentally new discipline in space science. After the publication of the scientific results from the Hipparcos mission in 1997, ESA adopted the Gaia mission, a follow-on and vastly more advanced star-mapping satellite, in 2000. Gaia was launched in 2013 and continues to operate from its advantageous location at the Sun-Earth Lagrange point, L2. Gaia is measuring the positions of more than two billion stars in our Galaxy with extreme accuracy, and is contributing profoundly to many areas of astronomy. The talk will explain why the measurement of star positions is of such scientific importance, recall its history, and present some of the many areas of astronomy that are being impacted by these latest state-of-the-art measurements. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Perryman is available for meetings by arrangement with his host, Ulrich Bastian (bastian@ari.uni-heidelberg.de)
Professor Michael Perryman (University College Dublin)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Large Lecture Hall (gHS)
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Abstract
The Hipparcos satellite project of the European Space Agency was dedicated to measuring the accurate positions of more than 100,000 stars. Doing so from space represented a fundamentally new discipline in space science. After the publication of the scientific results from the Hipparcos mission in 1997, ESA adopted the Gaia mission, a follow-on and vastly more advanced star-mapping satellite, in 2000. Gaia was launched in 2013 and continues to operate from its advantageous location at the Sun-Earth Lagrange point, L2. Gaia is measuring the positions of more than two billion stars in our Galaxy with extreme accuracy, and is contributing profoundly to many areas of astronomy. The talk will explain why the measurement of star positions is of such scientific importance, recall its history, and present some of the many areas of astronomy that are being impacted by these latest state-of-the-art measurements. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Perryman is available for meetings by arrangement with his host, Ulrich Bastian (bastian@ari.uni-heidelberg.de)
2023-06-27
16:00
16:00
Planet formation theory in the JWST era
Dr Bertram Bitsch (Max Planck Institut fuer Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
The overall framework for planet formation via the core accretion scenario can explain the vast majority of the occurrence rates of super-Earths/mini-Neptunes and gas giant planets. However, these planet formation models are now challenged by a new component: measurements of atmospheric abundances. It is thought that the atmospheric composition of planets holds key to their formation location, where especially the C/H, O/H and C/O of the atmospheres are key ingredients, as these ratios vary with orbital distance from the star due to the evaporation of different oxygen and carbon bearing species like H2O, CO2, CH4 and CO. In this talk I will present a state-of-the-art model that allows tracking of the chemical components of the disc and inside of growing planets. I will first explain the ingredients of this model and then show its applications to the composition of protoplanetary disc as well as of forming planets. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Bertram Bitsch (Max Planck Institut fuer Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
The overall framework for planet formation via the core accretion scenario can explain the vast majority of the occurrence rates of super-Earths/mini-Neptunes and gas giant planets. However, these planet formation models are now challenged by a new component: measurements of atmospheric abundances. It is thought that the atmospheric composition of planets holds key to their formation location, where especially the C/H, O/H and C/O of the atmospheres are key ingredients, as these ratios vary with orbital distance from the star due to the evaporation of different oxygen and carbon bearing species like H2O, CO2, CH4 and CO. In this talk I will present a state-of-the-art model that allows tracking of the chemical components of the disc and inside of growing planets. I will first explain the ingredients of this model and then show its applications to the composition of protoplanetary disc as well as of forming planets. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2023-06-20
16:00
16:00
Photodissociation Regions: Stars, Cars, and PDRs
Professor Mark Wolfire (University of Maryland, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Massive stars inject radiative and mechanical energy into their natal molecular cloud and surrounding interstellar medium that can both inhibit and initiate future star formation. The energy from these feedback processes are mainly deposited in and act upon the photodissociation region (PDR). PDRs are the regions where far-ultraviolet (FUV; 6 eV < h_nu < 13.6 eV) radiation from massive stars dominate the thermal processes or chemistry. The `Classic'' PDRs are at the interface between the HII region and the molecular cloud and also extend into the deeper molecular layers. PDRs however, appear in many other environments including reflection nebula planetary nebula, surfaces of pillars and globules, the diffuse interstellar medium, and in protostellar and protoplanetary disks. In fact most of the non stellar baryons in galaxies are in PDRs. Thus, understanding the physics and chemistry of PDRs through observation of the line and continuum radiation, through laboratory measurements, and through PDR modeling is critical for understanding the star formation history of the Universe. In this talk I will review the basic chemical and temperature structure of a PDR, discuss the heating and cooling processes, and note the dominant cooling lines that can be used to probe the physical conditions in the gas. I will discuss the analysis of PDR observations from diffuse gas, from the Orion Nebula Complex, and from the Orion Bar. In diffuse gas we use a recently measured rate for the dissociative recombination of OH+ to find the Galactic cosmic-ray ionization rate. In the Orion Nebula Complex we use the kinematic information to characterize the stellar feedback, and we zoom in on the structure, chemistry and physical conditions in the Orion Bar using recent JWST observations. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Wolfire is available for meetings by arrangement with his host, Melanie Chevance (chevance@uni-heidelberg.de).
Professor Mark Wolfire (University of Maryland, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Massive stars inject radiative and mechanical energy into their natal molecular cloud and surrounding interstellar medium that can both inhibit and initiate future star formation. The energy from these feedback processes are mainly deposited in and act upon the photodissociation region (PDR). PDRs are the regions where far-ultraviolet (FUV; 6 eV < h_nu < 13.6 eV) radiation from massive stars dominate the thermal processes or chemistry. The `Classic'' PDRs are at the interface between the HII region and the molecular cloud and also extend into the deeper molecular layers. PDRs however, appear in many other environments including reflection nebula planetary nebula, surfaces of pillars and globules, the diffuse interstellar medium, and in protostellar and protoplanetary disks. In fact most of the non stellar baryons in galaxies are in PDRs. Thus, understanding the physics and chemistry of PDRs through observation of the line and continuum radiation, through laboratory measurements, and through PDR modeling is critical for understanding the star formation history of the Universe. In this talk I will review the basic chemical and temperature structure of a PDR, discuss the heating and cooling processes, and note the dominant cooling lines that can be used to probe the physical conditions in the gas. I will discuss the analysis of PDR observations from diffuse gas, from the Orion Nebula Complex, and from the Orion Bar. In diffuse gas we use a recently measured rate for the dissociative recombination of OH+ to find the Galactic cosmic-ray ionization rate. In the Orion Nebula Complex we use the kinematic information to characterize the stellar feedback, and we zoom in on the structure, chemistry and physical conditions in the Orion Bar using recent JWST observations. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Wolfire is available for meetings by arrangement with his host, Melanie Chevance (chevance@uni-heidelberg.de).
2023-06-13
16:00
16:00
Measuring the properties of dark matter with strong lensing and JWST
Professor Anna Nierenberg (University of California, Merced)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Understanding the nature of dark matter is one of the major goals of modern physics. A key prediction of all dark matter models is that galaxies exist in extended dark matter halos. The abundance and density profiles of these halos depending directly on the physics of the candidate dark matter model. Strong gravitational lensing enables a direct measurement of these properties for halos at cosmological distances, without requiring halos to contain any baryons at all and thus provides a unique and powerful way to probe the nature of dark matter. I will present our recent results using strongly lensed quasar narrow-line emission to constrain the density profiles and mass function of dark matter halos and to provide some of the strongest constraints to date on warm-dark matter, self-interacting dark matter, and fuzzy dark matter models. I will also present new results from our ongoing JWST survey to measure strongly lensed quasar dusty torus flux ratios. I will conclude by discussing future prospects for strong gravitational lensing in the era of upcoming large surveys and the next generation of 30 meter class telescopes. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Nierenberg is available for meetings by arrangement with her hosts, Robert Schmidt (rschmidt@uni-heidelberg.de) and Joachim Wambsganss (jkw@ari.uni-heidelberg.de).
Professor Anna Nierenberg (University of California, Merced)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Understanding the nature of dark matter is one of the major goals of modern physics. A key prediction of all dark matter models is that galaxies exist in extended dark matter halos. The abundance and density profiles of these halos depending directly on the physics of the candidate dark matter model. Strong gravitational lensing enables a direct measurement of these properties for halos at cosmological distances, without requiring halos to contain any baryons at all and thus provides a unique and powerful way to probe the nature of dark matter. I will present our recent results using strongly lensed quasar narrow-line emission to constrain the density profiles and mass function of dark matter halos and to provide some of the strongest constraints to date on warm-dark matter, self-interacting dark matter, and fuzzy dark matter models. I will also present new results from our ongoing JWST survey to measure strongly lensed quasar dusty torus flux ratios. I will conclude by discussing future prospects for strong gravitational lensing in the era of upcoming large surveys and the next generation of 30 meter class telescopes. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Nierenberg is available for meetings by arrangement with her hosts, Robert Schmidt (rschmidt@uni-heidelberg.de) and Joachim Wambsganss (jkw@ari.uni-heidelberg.de).
2023-06-06
16:00
16:00
Star cluster formation, feedback and evolution across cosmic times
Professor Angela Adamo (Stockholm University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
In the era of multi wavelength surveys of unprecedented sensitivity and spatial resolution, we are now able to map star cluster formation from the very early phases (deeply embedded in their natal giant molecular clouds) as well as study their feedback on the interstellar medium not only in the local universe but across cosmic times. Gravitational telescopes and JWST capabilities have opened a new window for cluster studies in young galaxies. I will present our initial NIRCam imaging studies of star clusters and stellar clumps conducted in lensed galaxies between redshift 1 and 6 in the fields of A2744 and SMACS0723. Our results show a rapid evolution of stellar clump stellar densities and broad age ranges that help us to reconstruct the conditions where proto-globular clusters (proto-GCs) formed. We find evidence pointing toward proto-GC formation taking place in reionisation-era galaxies, hence, becoming important candidates to aid reionisation. However, these studies are limited to rest-frame optical wavelengths. The local universe remains a fundamental laboratory for understanding how rapid star clusters can emerge from their natal giant molecular clouds, thus whether they can leak copious amount of ionising photons. I will showcase some key results obtained from our initial JWST observations of the FEAST (Feedback in Emerging extrAgalactic Star clusTers, #1783) sample of nearby galaxies. Combinations of NIR and MIR colors as well as MIR emission lines like Br_alpha and the 3.35 micron PAH band help us to fully map the star clusters from deeply embedded phases to late stages, when AGB stars dominate their colors. We find that the emergence phase is mostly missed in HST optical-NIR studies and last about 4 Myr in our study case, NGC628. I will then present recent results obtained from the analyses of FUV-optical spectroscopy along with HST imaging which help us to understand how stellar feedback in star clusters determine the rapid evolution of HII regions and regulates the star formation cycle within galaxies. These studies, conducted in the local universe, remain a fundamental laboratory for understanding cluster formation and evolution in rapidly evolving galaxies across cosmic time. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Adamo is available for meetings by arrangement with her host, Kathryn Kreckel (Kathryn.Kreckel@uni-heidelberg.de).
Professor Angela Adamo (Stockholm University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
In the era of multi wavelength surveys of unprecedented sensitivity and spatial resolution, we are now able to map star cluster formation from the very early phases (deeply embedded in their natal giant molecular clouds) as well as study their feedback on the interstellar medium not only in the local universe but across cosmic times. Gravitational telescopes and JWST capabilities have opened a new window for cluster studies in young galaxies. I will present our initial NIRCam imaging studies of star clusters and stellar clumps conducted in lensed galaxies between redshift 1 and 6 in the fields of A2744 and SMACS0723. Our results show a rapid evolution of stellar clump stellar densities and broad age ranges that help us to reconstruct the conditions where proto-globular clusters (proto-GCs) formed. We find evidence pointing toward proto-GC formation taking place in reionisation-era galaxies, hence, becoming important candidates to aid reionisation. However, these studies are limited to rest-frame optical wavelengths. The local universe remains a fundamental laboratory for understanding how rapid star clusters can emerge from their natal giant molecular clouds, thus whether they can leak copious amount of ionising photons. I will showcase some key results obtained from our initial JWST observations of the FEAST (Feedback in Emerging extrAgalactic Star clusTers, #1783) sample of nearby galaxies. Combinations of NIR and MIR colors as well as MIR emission lines like Br_alpha and the 3.35 micron PAH band help us to fully map the star clusters from deeply embedded phases to late stages, when AGB stars dominate their colors. We find that the emergence phase is mostly missed in HST optical-NIR studies and last about 4 Myr in our study case, NGC628. I will then present recent results obtained from the analyses of FUV-optical spectroscopy along with HST imaging which help us to understand how stellar feedback in star clusters determine the rapid evolution of HII regions and regulates the star formation cycle within galaxies. These studies, conducted in the local universe, remain a fundamental laboratory for understanding cluster formation and evolution in rapidly evolving galaxies across cosmic time. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Professor Adamo is available for meetings by arrangement with her host, Kathryn Kreckel (Kathryn.Kreckel@uni-heidelberg.de).
2023-05-30
16:00
16:00
How to grow a galactic disk (or two)
Professor Florent Renaud (Lund Observatory, Sweden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture Theatre (gHS)
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Abstract
In the last years, observation programs and missions in all wavelengths have drastically improved the detailed and multi-dimensional surveying of galaxies. However, because of the heterogeneity of probes of the gaseous and stellar components, in the contemporary galaxies of the local Universe and the youngest objects at cosmic dawn, the construction of a complete, self-consistent scenario for the formation of a galaxy and its sub-structures has become an arduous task. This calls for a comprehensive theoretical framework, combining both large-scale effects and small details of galaxy formation in its cosmological context. In this talk, I will present a scenario for the formation of a Milky Way-like galaxy. Using a series of cosmological and galactic simulations, I will illustrate the successive phases in the assembly of the gaseous and stellar disks, and which detectable signatures these steps leave. I will particularly compare the contributions of intrinsic (internal) evolution and cosmological (external) effects in the formation of the galactic components and the associated stellar populations. I will highlight the paramount role of the coupling between the galactic and the cloud / stellar scales in setting the physical conditions of the star forming regions, and how this coupling evolves across cosmic time. I will discuss why some previous models of disk formation can be ruled out, and what the next generation of simulations and observation surveys could do to discriminate between the options still open, in our home Galaxy and others. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Florent is available for meetings by arrangement with his host, Genevieve Parmentier (gparm@ari.uni-heidelberg.de).
Professor Florent Renaud (Lund Observatory, Sweden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture Theatre (gHS)
Show/hide abstract
Abstract
In the last years, observation programs and missions in all wavelengths have drastically improved the detailed and multi-dimensional surveying of galaxies. However, because of the heterogeneity of probes of the gaseous and stellar components, in the contemporary galaxies of the local Universe and the youngest objects at cosmic dawn, the construction of a complete, self-consistent scenario for the formation of a galaxy and its sub-structures has become an arduous task. This calls for a comprehensive theoretical framework, combining both large-scale effects and small details of galaxy formation in its cosmological context. In this talk, I will present a scenario for the formation of a Milky Way-like galaxy. Using a series of cosmological and galactic simulations, I will illustrate the successive phases in the assembly of the gaseous and stellar disks, and which detectable signatures these steps leave. I will particularly compare the contributions of intrinsic (internal) evolution and cosmological (external) effects in the formation of the galactic components and the associated stellar populations. I will highlight the paramount role of the coupling between the galactic and the cloud / stellar scales in setting the physical conditions of the star forming regions, and how this coupling evolves across cosmic time. I will discuss why some previous models of disk formation can be ruled out, and what the next generation of simulations and observation surveys could do to discriminate between the options still open, in our home Galaxy and others. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Florent is available for meetings by arrangement with his host, Genevieve Parmentier (gparm@ari.uni-heidelberg.de).
2023-05-23
16:00
16:00
From spinning stars to black holes: Musings about the formation and evolution of star clusters
Dr Sebastian Kamann (Liverpool John Moores University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Throughout the last decades, our understanding of star formation and stellar evolution has been advanced by the study of star clusters. Nowadays this legacy is being continued with the help of integral field spectroscopy. Powerful instruments like MUSE have enabled us to study even the stars buried in the centres of dense globular clusters, and to gather spectroscopic samples rivaling their photometric counterparts in numbers. In my talk, I will illustrate some of the advances that we have achieved using MUSE data. By studying the kinematics of the stars and their spins, we gathered new insight into the formation of star clusters and the role played by angular momentum. On the other hand, studies of binary stars revealed some of the first stellar-mass black holes to be detected dynamically. Constraining their numbers in clusters is not only vital for understanding where binary black holes find each other and merge, but also for answering the question if the enigmatic intermediate-mass black holes are to be found in massive star clusters. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr. Kamann is available for meetings by arrangement with his hosts, Ivan Cabrera-Ziri (cabrera@uni-heidelberg.de) and Nadine Neumayer (neumayer@mpia.de).
Dr Sebastian Kamann (Liverpool John Moores University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
Throughout the last decades, our understanding of star formation and stellar evolution has been advanced by the study of star clusters. Nowadays this legacy is being continued with the help of integral field spectroscopy. Powerful instruments like MUSE have enabled us to study even the stars buried in the centres of dense globular clusters, and to gather spectroscopic samples rivaling their photometric counterparts in numbers. In my talk, I will illustrate some of the advances that we have achieved using MUSE data. By studying the kinematics of the stars and their spins, we gathered new insight into the formation of star clusters and the role played by angular momentum. On the other hand, studies of binary stars revealed some of the first stellar-mass black holes to be detected dynamically. Constraining their numbers in clusters is not only vital for understanding where binary black holes find each other and merge, but also for answering the question if the enigmatic intermediate-mass black holes are to be found in massive star clusters. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr. Kamann is available for meetings by arrangement with his hosts, Ivan Cabrera-Ziri (cabrera@uni-heidelberg.de) and Nadine Neumayer (neumayer@mpia.de).
2023-05-16
16:00
16:00
Which stars form black holes?
Dr Fabian Schneider (Heidelberg Institute for Theoretical Studies)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Black holes are some of the most fascinating objects in the Cosmos. They can form when massive stars collapse at the end of their lives. However, it remains unknown which stars form black holes and which explode in supernovae. The first stellar-mass black holes were identified in Galactic X-ray binaries, and mergers of black holes and neutron stars are nowadays routinely observed thanks to gravitational-wave detectors. With almost 100 observations of compact-object mergers, the mass distribution of stellar-mass black holes is being revealed across cosmic time. This will help better understand many aspects relevant to their formation such as supernova explosion physics and pre-supernova evolution of massive single and binary stars. In particular, the progenitor stars of most of the observed black holes were subject to envelope-stripping by binary mass transfer. This has severe consequences for the explodability of stars and hence the question of which stars form black holes. I will show that envelope stripping gives rise to characteristic black hole masses of 9 and 16 solar masses, and that there are hints of such a bimodality in current gravitational-wave observations. Furthermore, I will show how some of the most massive stellar-mass black holes may form from stars that merged with a companion during their evolution. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Fabian Schneider (Heidelberg Institute for Theoretical Studies)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
Black holes are some of the most fascinating objects in the Cosmos. They can form when massive stars collapse at the end of their lives. However, it remains unknown which stars form black holes and which explode in supernovae. The first stellar-mass black holes were identified in Galactic X-ray binaries, and mergers of black holes and neutron stars are nowadays routinely observed thanks to gravitational-wave detectors. With almost 100 observations of compact-object mergers, the mass distribution of stellar-mass black holes is being revealed across cosmic time. This will help better understand many aspects relevant to their formation such as supernova explosion physics and pre-supernova evolution of massive single and binary stars. In particular, the progenitor stars of most of the observed black holes were subject to envelope-stripping by binary mass transfer. This has severe consequences for the explodability of stars and hence the question of which stars form black holes. I will show that envelope stripping gives rise to characteristic black hole masses of 9 and 16 solar masses, and that there are hints of such a bimodality in current gravitational-wave observations. Furthermore, I will show how some of the most massive stellar-mass black holes may form from stars that merged with a companion during their evolution. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2023-05-09
16:00
16:00
The Extremely Large Telescope and its Instrumentation
Dr Joel Vernet (European Southern Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
With its 39-m diameter primary mirror, the Extremely Large Telescope is the largest optical /infrared currently under construction at Cerro Armazones in the Chilean Atacama desert. At the foci of this revolutionary telescope, a comprehensive suite of six versatile instruments designed to address a broad range of astrophysical questions is under development across many European institutes. In this talk, I will present an overview of the ELT project and show the latest progress on its construction. I will focus on some of the most difficult technical challenges we are facing to unleash the full potential of this giant eye on the sky. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr. Vernet is available for meetings by arrangement with his host, Dominika Wylezalek (dominika.wylezalek@uni-heidelberg.de).
Dr Joel Vernet (European Southern Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
With its 39-m diameter primary mirror, the Extremely Large Telescope is the largest optical /infrared currently under construction at Cerro Armazones in the Chilean Atacama desert. At the foci of this revolutionary telescope, a comprehensive suite of six versatile instruments designed to address a broad range of astrophysical questions is under development across many European institutes. In this talk, I will present an overview of the ELT project and show the latest progress on its construction. I will focus on some of the most difficult technical challenges we are facing to unleash the full potential of this giant eye on the sky. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr. Vernet is available for meetings by arrangement with his host, Dominika Wylezalek (dominika.wylezalek@uni-heidelberg.de).
2023-05-02
16:00
16:00
A Galactic View of Nucleosynthesis
Professor Jennifer Johnson (Ohio State University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
While we have known for decades that most f the elements are made in the lives and deaths of stars, there are many open questions, including the yields of core-collapse supernovae and the time-delay of Type Ia supernovae. Current theoretical models show large discrepancies depending on progenitor models and explosion mechanism. I will discuss new empirical measurements of supernova yields and timing from Galactic chemical evolution and individual core-collapse supernova remnants. I will review how the SDSS-V programs Milky Way Mapper and Local Volume Mapper can advance our study of nucleosynthesis. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Johnson is available for meetings by arrangement with her host, Saskia Hekker (saskia.hekker@h-its.org).
Professor Jennifer Johnson (Ohio State University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
Show/hide abstract
Abstract
While we have known for decades that most f the elements are made in the lives and deaths of stars, there are many open questions, including the yields of core-collapse supernovae and the time-delay of Type Ia supernovae. Current theoretical models show large discrepancies depending on progenitor models and explosion mechanism. I will discuss new empirical measurements of supernova yields and timing from Galactic chemical evolution and individual core-collapse supernova remnants. I will review how the SDSS-V programs Milky Way Mapper and Local Volume Mapper can advance our study of nucleosynthesis. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Johnson is available for meetings by arrangement with her host, Saskia Hekker (saskia.hekker@h-its.org).
2023-04-25
16:00
16:00
Early Science from the "Physics at High Angular Resolution in Nearby Galaxies" JWST Treasury
Professor Karin Sandstrom (UC San Diego, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
JWST observations of nearby galaxies reveal the physics of the interstellar medium and star formation in stunning detail. I will present results from a large Treasury survey of nearby galaxies called the "Physics at High Angular Resolution in Nearby Galaxies Survey" (PHANGS). The new JWST images of 19 nearby galaxies reveal a wealth of detail: embedded star clusters, pervasive filamentary structure, and a multitude of bubbles and shells throughout the ISM. I will highlight some of the key early science results from our survey, including new insights into the behavior of small dust grains called polycyclic aromatic hydrocarbons; characterization of filaments and bubbles; the relationship between mid-infrared emission, gas, and star formation; discovery of deeply embedded, newly formed star clusters; constraints on the lifetimes of molecular clouds; and more. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Sandstrom is available for meetings by arrangement with her hosts, Kathryn Kreckel (Kathryn.Kreckel@uni-heidelberg.de) and Justus Neumann (jneumann@mpia.de).
Professor Karin Sandstrom (UC San Diego, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture hall (gHS)
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Abstract
JWST observations of nearby galaxies reveal the physics of the interstellar medium and star formation in stunning detail. I will present results from a large Treasury survey of nearby galaxies called the "Physics at High Angular Resolution in Nearby Galaxies Survey" (PHANGS). The new JWST images of 19 nearby galaxies reveal a wealth of detail: embedded star clusters, pervasive filamentary structure, and a multitude of bubbles and shells throughout the ISM. I will highlight some of the key early science results from our survey, including new insights into the behavior of small dust grains called polycyclic aromatic hydrocarbons; characterization of filaments and bubbles; the relationship between mid-infrared emission, gas, and star formation; discovery of deeply embedded, newly formed star clusters; constraints on the lifetimes of molecular clouds; and more. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Sandstrom is available for meetings by arrangement with her hosts, Kathryn Kreckel (Kathryn.Kreckel@uni-heidelberg.de) and Justus Neumann (jneumann@mpia.de).
2023-02-14
16:00
16:00
Theoretical modelling of star forming galaxies and AGN in the JWST and ELT era
Professor Lisa Kewley (Center for Astrophysics, Harvard University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Large lecture hall (gHS)
Professor Lisa Kewley (Center for Astrophysics, Harvard University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Large lecture hall (gHS)
2023-02-07
16:00
16:00
Untangling Galaxy Evolution in the New Spectroscopic Era
Professor Allison Strom (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Large lecture hall (gHS)
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Abstract
A central goal of modern astrophysics is to understand how galaxies grow and change over the 14 Gym of cosmic history. To achieve this goal, it is necessary to disentangle the competing effects of the many baryonic processes that govern galaxy evolution alongside the dark matter-dominated growth of large-scale structure---including accretion of gas from the cosmic web, as well as outflows and feedback driven by massive stars and accreting supermassive black holes. These processes are difficult to observe directly, and an added complication is that much of what we know about the galaxy population is based on the present-day Universe (z~0), even though the vast majority of stars in galaxies were formed at much earlier times (z>1, more than ~7 Gyr ago). Fortunately, using new facilities like the James Webb Space Telescope (JWST) and premier ground-based observatories like the Keck Telescopes, we are now on the cusp of being able to study galaxies in detail at all cosmic times. I will share recent progress in characterizing the galaxy population during the peak of galaxy assembly 10-12 Gyr ago (z~2-3), including efforts by my group to use extremely deep Cycle 1 JWST/NIRSpec observations to accurately determine the chemical abundances in these distant galaxies. I will also preview science that will soon be possible with a large upcoming galaxy survey using the new Prime Focus Spectrograph (PFS) on the Subaru Telescope, which will target hundreds of thousands of galaxies during the period 5-10 Gyr ago when many were transitioning from highly star-forming to relatively quiescent, like the majority of galaxies today. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Strom is visiting the Max-Planck Institute fuer Astronomy, and is available for meetings by arrangement with her host, (banados@mpia.de).
Professor Allison Strom (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Large lecture hall (gHS)
Show/hide abstract
Abstract
A central goal of modern astrophysics is to understand how galaxies grow and change over the 14 Gym of cosmic history. To achieve this goal, it is necessary to disentangle the competing effects of the many baryonic processes that govern galaxy evolution alongside the dark matter-dominated growth of large-scale structure---including accretion of gas from the cosmic web, as well as outflows and feedback driven by massive stars and accreting supermassive black holes. These processes are difficult to observe directly, and an added complication is that much of what we know about the galaxy population is based on the present-day Universe (z~0), even though the vast majority of stars in galaxies were formed at much earlier times (z>1, more than ~7 Gyr ago). Fortunately, using new facilities like the James Webb Space Telescope (JWST) and premier ground-based observatories like the Keck Telescopes, we are now on the cusp of being able to study galaxies in detail at all cosmic times. I will share recent progress in characterizing the galaxy population during the peak of galaxy assembly 10-12 Gyr ago (z~2-3), including efforts by my group to use extremely deep Cycle 1 JWST/NIRSpec observations to accurately determine the chemical abundances in these distant galaxies. I will also preview science that will soon be possible with a large upcoming galaxy survey using the new Prime Focus Spectrograph (PFS) on the Subaru Telescope, which will target hundreds of thousands of galaxies during the period 5-10 Gyr ago when many were transitioning from highly star-forming to relatively quiescent, like the majority of galaxies today. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Strom is visiting the Max-Planck Institute fuer Astronomy, and is available for meetings by arrangement with her host, (banados@mpia.de).
2023-01-31
16:00
16:00
Early galaxies and black holes: the first six months from the JWST NIRSpec GTO programme
Professor Roberto Maiolino (Kavli Institute for Cosmology, Cambridge, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
The successful launch, deployment and commissioning of the James Webb Space Telescope has opened a new era in astronomy and astrophysics. Indeed, in some infrared spectral bands, Webb's sensitivity is up to three orders of magnitude higher than previous facilities. Such a huge leap in sensitivity has happened very rarely in the history of astronomy and, even more broadly, in the history of science. The first observations released by this fantastic observatory have not disappointed, by delivering several unexpected results. I will give an overview of the early, exciting Webb's findings by focusing on some the new results on distant galaxies and primeval black holes, primarily based on the first datasets obtained through the extensive GTO programme of the NIRSpec instrument. The observations reveal, in the first billion year of life of the Universe, an emerging population of galaxies with properties significantly different from those seen at later epochs. I will show that some of these datasets nicely confirm, for the first time, some expectations from models and cosmological simulations on galaxy formation and transformation. However, I will also show some puzzling results that are challenging to explain with current models. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Maiolino is available for meetings by arrangement with his host, Dylan Nelson (dnelson@uni-heidelberg.de).
Professor Roberto Maiolino (Kavli Institute for Cosmology, Cambridge, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
Show/hide abstract
Abstract
The successful launch, deployment and commissioning of the James Webb Space Telescope has opened a new era in astronomy and astrophysics. Indeed, in some infrared spectral bands, Webb's sensitivity is up to three orders of magnitude higher than previous facilities. Such a huge leap in sensitivity has happened very rarely in the history of astronomy and, even more broadly, in the history of science. The first observations released by this fantastic observatory have not disappointed, by delivering several unexpected results. I will give an overview of the early, exciting Webb's findings by focusing on some the new results on distant galaxies and primeval black holes, primarily based on the first datasets obtained through the extensive GTO programme of the NIRSpec instrument. The observations reveal, in the first billion year of life of the Universe, an emerging population of galaxies with properties significantly different from those seen at later epochs. I will show that some of these datasets nicely confirm, for the first time, some expectations from models and cosmological simulations on galaxy formation and transformation. However, I will also show some puzzling results that are challenging to explain with current models. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Maiolino is available for meetings by arrangement with his host, Dylan Nelson (dnelson@uni-heidelberg.de).
2023-01-24
16:00
16:00
Connecting Exoplanet Properties to Planet Formation: a New Paradigm Emerges
Prof. Ralph E. Pudritz (McMaster University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre,
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Abstract
One of the great challenges of exoplanetary astrophysics is to understand how the observed properties of exoplanets – their masses, orbital characteristics, bulk properties and atmospheric composition – arise as a consequence of how planets are formed in protoplanetary disks. Where and what materials planets accrete from the disk depends in part upon how they migrate and how the gas and dust in the disks evolve both chemically and dynamically. The vast majority of papers over the last decades have assumed that disk turbulence is the fundamental driver of most of these processes. Recent theoretical and observational advances however point to the importance of the ubiquitous protostellar outflows, now shown observationally to be magnetohydrodynamical disk winds, as the key player. In this talk I will discuss the recent advances in observations, theory, and simulations of planet formation and explore the relative importance of disk winds versus turbulence in controlling planet formation and the observed properties and compositions of exoplanetary populations. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Pudritz is visiting the Institut fuer Theoretisches Astrophysik and is available for meetings by arrangement with his host, Ralf Klessen (klessen@uni-heidelberg.de).
Prof. Ralph E. Pudritz (McMaster University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre,
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Abstract
One of the great challenges of exoplanetary astrophysics is to understand how the observed properties of exoplanets – their masses, orbital characteristics, bulk properties and atmospheric composition – arise as a consequence of how planets are formed in protoplanetary disks. Where and what materials planets accrete from the disk depends in part upon how they migrate and how the gas and dust in the disks evolve both chemically and dynamically. The vast majority of papers over the last decades have assumed that disk turbulence is the fundamental driver of most of these processes. Recent theoretical and observational advances however point to the importance of the ubiquitous protostellar outflows, now shown observationally to be magnetohydrodynamical disk winds, as the key player. In this talk I will discuss the recent advances in observations, theory, and simulations of planet formation and explore the relative importance of disk winds versus turbulence in controlling planet formation and the observed properties and compositions of exoplanetary populations. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Pudritz is visiting the Institut fuer Theoretisches Astrophysik and is available for meetings by arrangement with his host, Ralf Klessen (klessen@uni-heidelberg.de).
2023-01-17
16:00
16:00
Measuring Hubble's Constant to 1 percent using Pulsating Stars
Dr. Richard Anderson (Ecole Polytechnique Federale de Lausanne, Switzerland)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
Hubble's constant, H0, quantifies the expansion rate of the Universe today and is of fundamental importance for cosmology. For example, H0 is related to the age of the Universe, its observable size, and its critical density, among others. Yet, recent observations have established a 5 sigma discrepancy between H0 measured in the local Universe and the value predicted by flat Lambda CDM cosmology based on observations of the early Universe. To clarify this looming cosmological crisis, the H1PStars project seeks to measure H0 to an accuracy of 1% using stellar standard candles that calibrate the absolute magnitudes of type-Ia supernovae. Starting with a brief overview of the current Hubble tension, I will discuss recent improvements in the calibration of and upcoming opportunities for the nearest rungs of the distance ladder. In turn, I will discuss ongoing work to improve the absolute calibration of Cepheid luminosities, to mitigate biases affecting Cepheid distances, and to obtain new insights into Cepheid stars from a stellar variability perspective that will help to improve our astrophysical basis for using Cepheids as highly accurate distance tracers. I will close by discussing these improvements in the context of the 1% measurement of Hubble?s constant required to understand the ongoing cosmological crisis. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr. Anderson will be based at the ARI institute for his visit to Heidelberg and will be available for meetings by arrangement with his host, Dominika Wylezalek (dominika.wylezalek@uni-heidelberg.de).
Dr. Richard Anderson (Ecole Polytechnique Federale de Lausanne, Switzerland)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
Show/hide abstract
Abstract
Hubble's constant, H0, quantifies the expansion rate of the Universe today and is of fundamental importance for cosmology. For example, H0 is related to the age of the Universe, its observable size, and its critical density, among others. Yet, recent observations have established a 5 sigma discrepancy between H0 measured in the local Universe and the value predicted by flat Lambda CDM cosmology based on observations of the early Universe. To clarify this looming cosmological crisis, the H1PStars project seeks to measure H0 to an accuracy of 1% using stellar standard candles that calibrate the absolute magnitudes of type-Ia supernovae. Starting with a brief overview of the current Hubble tension, I will discuss recent improvements in the calibration of and upcoming opportunities for the nearest rungs of the distance ladder. In turn, I will discuss ongoing work to improve the absolute calibration of Cepheid luminosities, to mitigate biases affecting Cepheid distances, and to obtain new insights into Cepheid stars from a stellar variability perspective that will help to improve our astrophysical basis for using Cepheids as highly accurate distance tracers. I will close by discussing these improvements in the context of the 1% measurement of Hubble?s constant required to understand the ongoing cosmological crisis. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr. Anderson will be based at the ARI institute for his visit to Heidelberg and will be available for meetings by arrangement with his host, Dominika Wylezalek (dominika.wylezalek@uni-heidelberg.de).
2023-01-10
16:00
16:00
How heavy is the most massive star?
Professor Jorick Vink (Armagh Observatory, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
Very massive stars (VMS) are dominant sources of ionising radiation. The prime difference between VMS in our local Universe and those in the Early Universe is their metallicity (Z), which leads to differences in mass loss and evolution, but also to different amounts of ionising flux, black hole masses, and the effective stellar upper-mass limit. HST is observing hundreds of massive stars in the Small and Large Magellanic Clouds (SMC & LMC) under the ULLYSES programme to study the winds and feedback of low-Z stars. Radiation-driven wind theory predicts a strong dependence of their strength on the host galaxy Z, and while initial studies support the predicted mass-loss-Z dependence, ULLYSES and its optical counterpart "X-SHOOTING ULLYSES" are testing this on a large sample for the first time. X-Shooting Ullyses will have massive consequences for our understanding of massive-star formation and evolution, feedback, and gravitational-wave events at low Z, which I place into Cosmological context. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Vink will be based at the Astronomisches Rechen-Institut during his visit to Heidelberg, and will be available for meetings by arrangement with his host, Andreas Sander (andreas.sander@uni-heidelberg.de).
Professor Jorick Vink (Armagh Observatory, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
Show/hide abstract
Abstract
Very massive stars (VMS) are dominant sources of ionising radiation. The prime difference between VMS in our local Universe and those in the Early Universe is their metallicity (Z), which leads to differences in mass loss and evolution, but also to different amounts of ionising flux, black hole masses, and the effective stellar upper-mass limit. HST is observing hundreds of massive stars in the Small and Large Magellanic Clouds (SMC & LMC) under the ULLYSES programme to study the winds and feedback of low-Z stars. Radiation-driven wind theory predicts a strong dependence of their strength on the host galaxy Z, and while initial studies support the predicted mass-loss-Z dependence, ULLYSES and its optical counterpart "X-SHOOTING ULLYSES" are testing this on a large sample for the first time. X-Shooting Ullyses will have massive consequences for our understanding of massive-star formation and evolution, feedback, and gravitational-wave events at low Z, which I place into Cosmological context. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Vink will be based at the Astronomisches Rechen-Institut during his visit to Heidelberg, and will be available for meetings by arrangement with his host, Andreas Sander (andreas.sander@uni-heidelberg.de).
2022-12-13
16:00
16:00
Exploring the Diversity of Exoplanet Atmospheres
Dr Hannah Wakeford (University of Bristol, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
The study of exoplanets, planets that orbit stars other than the Sun, is at the forefront of the public imagination in space and an exciting field of research. The question "how do stars and planetary systems form and evolve?" is one of the biggest in Astronomy, and is at the root of one of the most important questions in science today: "How did we get here?". To resolve these questions we need to observe, interpret, and understand the nature of planets beyond our Solar System. In this talk I will go through the methods, observations, and the physics behind some of the interpretations we are making about the nature of these strange new worlds. As an observer I will show some of the work we have been doing measuring the transmission spectra of giant exoplanet atmospheres looking for the tale-tale absorption of water vapor and the presence of exotic clouds. I will discuss some of the challenges associated with the measurement of atmospheric abundances, a brief look at the role clouds can play in understanding dynamics and chemistry, and what future measurements can help further constrain our understanding of planetary atmospheres. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Wakeford will be based at the Max-Planck Institut fuer Astronomie during her visit to Heidelberg, and will be available for meetings by arrangement with her host, Laura Kreidberg (kreidberg@mpia.de).
Dr Hannah Wakeford (University of Bristol, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
Show/hide abstract
Abstract
The study of exoplanets, planets that orbit stars other than the Sun, is at the forefront of the public imagination in space and an exciting field of research. The question "how do stars and planetary systems form and evolve?" is one of the biggest in Astronomy, and is at the root of one of the most important questions in science today: "How did we get here?". To resolve these questions we need to observe, interpret, and understand the nature of planets beyond our Solar System. In this talk I will go through the methods, observations, and the physics behind some of the interpretations we are making about the nature of these strange new worlds. As an observer I will show some of the work we have been doing measuring the transmission spectra of giant exoplanet atmospheres looking for the tale-tale absorption of water vapor and the presence of exotic clouds. I will discuss some of the challenges associated with the measurement of atmospheric abundances, a brief look at the role clouds can play in understanding dynamics and chemistry, and what future measurements can help further constrain our understanding of planetary atmospheres. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Wakeford will be based at the Max-Planck Institut fuer Astronomie during her visit to Heidelberg, and will be available for meetings by arrangement with her host, Laura Kreidberg (kreidberg@mpia.de).
2022-11-29
16:00
16:00
The connection(s) between galaxies and their gaseous halos
Dr Dylan Nelson (Institut für Theoretische Astrophysik, Heidelberg University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
I will discuss our recent theoretical investigations on how stellar and supermassive black hole feedback within galaxies directly affects their surrounding gaseous halos, and the observable signatures of this circumgalactic media, within modern large-volume cosmological magnetohydrodynamical simulations.
Dr Dylan Nelson (Institut für Theoretische Astrophysik, Heidelberg University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
I will discuss our recent theoretical investigations on how stellar and supermassive black hole feedback within galaxies directly affects their surrounding gaseous halos, and the observable signatures of this circumgalactic media, within modern large-volume cosmological magnetohydrodynamical simulations.
2022-11-22
16:00
16:00
Our X-ray view of the Milky Way center, its outflow, and the circumgalactic medium
Dr Gabriele Ponti (INAF - Osservatorio Astronomico di Brera)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
Being located at only ~8 kpc from us, the center of our Galaxy provides us with the unique opportunity to study the physics occurring in the core of normal galaxies at very high spatial resolution. Thanks to its penetrating power, the X-ray band is particularly suited for studies of the Galactic center, allowing us to have a direct view of the central heart of the Milky Way. Over the past years, evidence has mounted that outflows of matter and energy from the core of our Milky Way have shaped the observed structure of the Galaxy on a variety of larger scales. On the one hand, within the central few square degrees of the Galaxy, X-ray maps have discovered two prominent X-ray structures extending hundreds of parsecs above and below the plane, which appear to connect the Galactic Centre region to the Fermi bubbles. On the other hand, large scale X-ray maps have revealed that the Galactic outflow is at least ten times more extended and energetic than previously thought, indicating that activity in the core of the Milky Way can have a profound effect on its circumgalactic medium. In this talk, I will review our current knowledge of the X-ray emission from the Milky Way center, the Galactic outflow and the hot phase of the circumgalactic medium. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Ponti will be based at the Institut fuer Theoretische Astrophysik during his visit to Heidelberg, and will be available for meetings by arrangement with his host, Mattia Sormani (mattia.sormani@uni-heidelberg.de).
Dr Gabriele Ponti (INAF - Osservatorio Astronomico di Brera)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
Show/hide abstract
Abstract
Being located at only ~8 kpc from us, the center of our Galaxy provides us with the unique opportunity to study the physics occurring in the core of normal galaxies at very high spatial resolution. Thanks to its penetrating power, the X-ray band is particularly suited for studies of the Galactic center, allowing us to have a direct view of the central heart of the Milky Way. Over the past years, evidence has mounted that outflows of matter and energy from the core of our Milky Way have shaped the observed structure of the Galaxy on a variety of larger scales. On the one hand, within the central few square degrees of the Galaxy, X-ray maps have discovered two prominent X-ray structures extending hundreds of parsecs above and below the plane, which appear to connect the Galactic Centre region to the Fermi bubbles. On the other hand, large scale X-ray maps have revealed that the Galactic outflow is at least ten times more extended and energetic than previously thought, indicating that activity in the core of the Milky Way can have a profound effect on its circumgalactic medium. In this talk, I will review our current knowledge of the X-ray emission from the Milky Way center, the Galactic outflow and the hot phase of the circumgalactic medium. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Ponti will be based at the Institut fuer Theoretische Astrophysik during his visit to Heidelberg, and will be available for meetings by arrangement with his host, Mattia Sormani (mattia.sormani@uni-heidelberg.de).
2022-11-15
16:00
16:00
Molecular Astrophysics at the Cryogenic Storage Ring
Dr Holger Kreckel (Max-Planck-Institut für Kernphysik)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
About 270 different molecular species have been identified in space, and this number continues to grow steadily. The surprising molecular diversity bears witness to an active reaction network, in which molecular ions are the main drivers of chemistry in the gas phase. While the advanced capabilities of modern telescopes may help us to unravel the molecular composition of the universe, to gain a comprehensive understanding of the observational results requires detailed knowledge of the molecular formation, excitation, and destruction mechanisms. However, laboratory studies of many fundamental reactions that dominate the chemistry of interstellar space are still a major challenge. In this framework, the Cryogenic Storage Ring (CSR), operated at the Max Planck Institute for Nuclear Physics in Heidelberg, serves as a unique testbench to study cold molecular ions in the gas phase. With a circumference of 35m, temperatures below 10K, and residual gas densities on the order of 103 cm-3, the CSR is currently the largest and most ambitious electrostatic storage ring project in the world. Its experimental stations allow for merged beams collision studies involving molecular ions, neutral atoms, free electrons, and photons under true interstellar conditions. I will present the instrumental capabilities of the CSR, together with recent results with relevance to astrophysics and perspectives for future experiments. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Holger Kreckel (Max-Planck-Institut für Kernphysik)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
Show/hide abstract
Abstract
About 270 different molecular species have been identified in space, and this number continues to grow steadily. The surprising molecular diversity bears witness to an active reaction network, in which molecular ions are the main drivers of chemistry in the gas phase. While the advanced capabilities of modern telescopes may help us to unravel the molecular composition of the universe, to gain a comprehensive understanding of the observational results requires detailed knowledge of the molecular formation, excitation, and destruction mechanisms. However, laboratory studies of many fundamental reactions that dominate the chemistry of interstellar space are still a major challenge. In this framework, the Cryogenic Storage Ring (CSR), operated at the Max Planck Institute for Nuclear Physics in Heidelberg, serves as a unique testbench to study cold molecular ions in the gas phase. With a circumference of 35m, temperatures below 10K, and residual gas densities on the order of 103 cm-3, the CSR is currently the largest and most ambitious electrostatic storage ring project in the world. Its experimental stations allow for merged beams collision studies involving molecular ions, neutral atoms, free electrons, and photons under true interstellar conditions. I will present the instrumental capabilities of the CSR, together with recent results with relevance to astrophysics and perspectives for future experiments. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-11-08
16:00
16:00
How the Sun and its siblings were born as a family but drifted apart
Professor Simon Portegies Zwart (Sterrewacht Leiden)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
Most stars are born in clustered environments, and the Solar system was probably not an exception. There is considerable evidence supporting this argument, including the high abundance of 26-Aluminum in short-lived radionuclides, the existence of Sedna-similar asteroids, retrograde orbiting TNOs, the tilting of the Ecliptic, and the scarred outer edge of the Kuiper belt. Some sibling cluster members may still be in the Sun's vicinity. But if our neighboring stars so strongly influenced the early Solar system, why do we have an Oort cloud? The parent cluster dissolved in the Galactic tidal field long ago, but can we find our siblings back based on their orbits in the Galactic potential or chemical composition? Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Portegies Zwart will be based at the ITA institute for his visit to Heidelberg and will be available for meetings by arrangement with his host, Ralf Klessen (klessen@uni-heidelberg.de).
Professor Simon Portegies Zwart (Sterrewacht Leiden)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
Most stars are born in clustered environments, and the Solar system was probably not an exception. There is considerable evidence supporting this argument, including the high abundance of 26-Aluminum in short-lived radionuclides, the existence of Sedna-similar asteroids, retrograde orbiting TNOs, the tilting of the Ecliptic, and the scarred outer edge of the Kuiper belt. Some sibling cluster members may still be in the Sun's vicinity. But if our neighboring stars so strongly influenced the early Solar system, why do we have an Oort cloud? The parent cluster dissolved in the Galactic tidal field long ago, but can we find our siblings back based on their orbits in the Galactic potential or chemical composition? Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Portegies Zwart will be based at the ITA institute for his visit to Heidelberg and will be available for meetings by arrangement with his host, Ralf Klessen (klessen@uni-heidelberg.de).
2022-10-25
16:00
16:00
The Sun as a Variable Star
Professor Sarbani Basu (Yale University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut (Philosophenweg 12), Large lecture theatre
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Abstract
We live in the backyard of a star. Although generally not classified as such, the Sun is a variable star. The appearance of the Sun changes with time. We now have helioseismology data covering more than two solar cycles that have revealed that solar interior changes too. In this talk, I shall discuss what we have learned about what has changed in the Sun and the mysteries that have been revealed. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Basu will be based at the HITS institute for her visit to Heidelberg and will be available for meetings by arrangement with her host, Prof. Friedrich Roepke (roepke@uni-heidelberg.de).
Professor Sarbani Basu (Yale University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut (Philosophenweg 12), Large lecture theatre
Show/hide abstract
Abstract
We live in the backyard of a star. Although generally not classified as such, the Sun is a variable star. The appearance of the Sun changes with time. We now have helioseismology data covering more than two solar cycles that have revealed that solar interior changes too. In this talk, I shall discuss what we have learned about what has changed in the Sun and the mysteries that have been revealed. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Basu will be based at the HITS institute for her visit to Heidelberg and will be available for meetings by arrangement with her host, Prof. Friedrich Roepke (roepke@uni-heidelberg.de).
2022-10-18
16:00
16:00
Testing theories of regulated star formation in clumpy, gas-rich disk galaxies
Professor Deanne Fisher (Center for Astrophysics and Supercomputing, Swinburne University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut (Philosophenweg 12), Large lecture theatre
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Abstract
Over 2/3 of all star formation in the Universe occurs in gas-rich, super-high pressure clumpy galaxies in the epoch of redshift z~1-3. However, because these galaxies are so distant, we are limited in the information available to study the properties of star formation and gas in these systems. I will present results using a sample of extremely rare, nearby galaxies (from the DYNAMO survey and the new DUVET survey) that are very well matched in gas fraction, kinematics, structure and morphology to z=1-2 main-sequence galaxies. We use these galaxies as laboratories to study the processes inside galaxies in the dominate mode of star formation in the Universe. In this talk I will report on results that are aimed at testing models of star formation in galaxies. Feedback regulated star formation theories aim to explain properties like the velocity dispersion of disks, the relationship between gas and star formation and the vertical scale height of thin disks in galaxies. I will make direct comparisons to the expectations of these theories to our observations. I will discuss my group's very recent efforts to connect the regulation of gas via outflows to the picture of how galaxies maintain their star formation rates and positions in Kennicutt-Schmidt relationship. Finally, I will argue that the next step we need is observations of the multiphase ISM and outflows, and discuss the new large VLT program GECKOS that is intended to do just that. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Fisher will be based at the ARI institute for her visit to Heidelberg and will be available for meetings by arrangement with her host, Kathryn Kreckel (kathryn.kreckel@uni-heidelberg.de).
Professor Deanne Fisher (Center for Astrophysics and Supercomputing, Swinburne University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut (Philosophenweg 12), Large lecture theatre
Show/hide abstract
Abstract
Over 2/3 of all star formation in the Universe occurs in gas-rich, super-high pressure clumpy galaxies in the epoch of redshift z~1-3. However, because these galaxies are so distant, we are limited in the information available to study the properties of star formation and gas in these systems. I will present results using a sample of extremely rare, nearby galaxies (from the DYNAMO survey and the new DUVET survey) that are very well matched in gas fraction, kinematics, structure and morphology to z=1-2 main-sequence galaxies. We use these galaxies as laboratories to study the processes inside galaxies in the dominate mode of star formation in the Universe. In this talk I will report on results that are aimed at testing models of star formation in galaxies. Feedback regulated star formation theories aim to explain properties like the velocity dispersion of disks, the relationship between gas and star formation and the vertical scale height of thin disks in galaxies. I will make direct comparisons to the expectations of these theories to our observations. I will discuss my group's very recent efforts to connect the regulation of gas via outflows to the picture of how galaxies maintain their star formation rates and positions in Kennicutt-Schmidt relationship. Finally, I will argue that the next step we need is observations of the multiphase ISM and outflows, and discuss the new large VLT program GECKOS that is intended to do just that. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Prof. Fisher will be based at the ARI institute for her visit to Heidelberg and will be available for meetings by arrangement with her host, Kathryn Kreckel (kathryn.kreckel@uni-heidelberg.de).
2022-09-05
12:40
12:40
2022-07-26
16:00
16:00
The origin and evolution of close-in exoplanets
Dr James Owen (Imperial College London, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
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Abstract
The last decade has taught us exoplanets with radii between 1 and4 Earth radii and orbital periods < 100 days are extremely common, with the majority of stars hosting at least one of these planets. The planets were not predicted by our early planet formation models conditioned on explaining the Solar System. Many of these planets are so low density that the only way to explain their current structure is that they host large, but low mass hydrogen dominated atmospheres. One suggestion for the origin of these planets is that the majority were born with hydrogen dominated atmospheres and that a fraction lost these atmospheres due to photo evaporative driven mass-loss. I will discuss the theory behind this evolutionary pathway; how we can use it to extract the properties of the planet?s when they were born and well as discussing the compositional imprints this process leaves behind in the remaining atmospheres. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Owen will be based at MPIAstronomie for his visit to Heidelberg and will be available for meetings by arrangement with his host, Laura Kreidberg (kreidberg@mpia.de).
Dr James Owen (Imperial College London, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
Show/hide abstract
Abstract
The last decade has taught us exoplanets with radii between 1 and4 Earth radii and orbital periods < 100 days are extremely common, with the majority of stars hosting at least one of these planets. The planets were not predicted by our early planet formation models conditioned on explaining the Solar System. Many of these planets are so low density that the only way to explain their current structure is that they host large, but low mass hydrogen dominated atmospheres. One suggestion for the origin of these planets is that the majority were born with hydrogen dominated atmospheres and that a fraction lost these atmospheres due to photo evaporative driven mass-loss. I will discuss the theory behind this evolutionary pathway; how we can use it to extract the properties of the planet?s when they were born and well as discussing the compositional imprints this process leaves behind in the remaining atmospheres. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 Dr Owen will be based at MPIAstronomie for his visit to Heidelberg and will be available for meetings by arrangement with his host, Laura Kreidberg (kreidberg@mpia.de).
2022-07-19
16:00
16:00
Imaging Supermassive Black Holes with the Event Horizon Telescope
Dr Shep Doeleman (Center for Astrophysics, Harvard University, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
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Abstract
Black holes are cosmic objects so small and dense, that nothing, not even light can escape their gravitational pull. Until recently, no one had ever seen what a black hole actually looked like. Einstein's theories predict that a distant observer should see a ring of light encircling the black hole, which forms when radiation emitted by infalling hot gas is lensed by the extreme gravity near the event horizon. On April 10th, 2019, the EHT project reported success: using a global network of radio dishes we have imaged the 6.5 billion solar mass black hole in galaxy M87, and we have seen the predicted strong gravitational lensing that confirms the theory of General Relativity at the boundary of a black hole. This was followed up on May 12th, 2022 by the first image of, SgrA*, the 4 million solar mass black hole in the center of the Milky way. This talk will cover how this was accomplished, details of the first results, as well as future directions that will enable real-time black hole movies. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Shep Doeleman (Center for Astrophysics, Harvard University, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
Show/hide abstract
Abstract
Black holes are cosmic objects so small and dense, that nothing, not even light can escape their gravitational pull. Until recently, no one had ever seen what a black hole actually looked like. Einstein's theories predict that a distant observer should see a ring of light encircling the black hole, which forms when radiation emitted by infalling hot gas is lensed by the extreme gravity near the event horizon. On April 10th, 2019, the EHT project reported success: using a global network of radio dishes we have imaged the 6.5 billion solar mass black hole in galaxy M87, and we have seen the predicted strong gravitational lensing that confirms the theory of General Relativity at the boundary of a black hole. This was followed up on May 12th, 2022 by the first image of, SgrA*, the 4 million solar mass black hole in the center of the Milky way. This talk will cover how this was accomplished, details of the first results, as well as future directions that will enable real-time black hole movies. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-07-12
16:00
16:00
The new era of stellar physics
Dr Matteo Cantiello (Center for Computational Astrophysics, Flatiron Institute, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
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Abstract
Stellar astrophysics is undergoing a renaissance driven by new observational and theoretical capabilities. Wide-field time-domain surveys have uncovered new classes of stellar explosions, helping to understand how stars evolve and end their lives. Gravitational-wave astronomy is providing exciting insights into the properties of the final remnants of massive stars. Asteroseismology, the study of waves in stars, is also producing dramatic breakthroughs in stellar structure and evolution. Thanks to space astrometry, accurate distances are now available for an unprecedented number of galactic stars. From a theoretical standpoint, it is increasingly possible to study aspects of the three-dimensional structure of stars using targeted numerical simulations. These studies can then be used to develop more accurate models of these physics in one-dimensional stellar evolution codes. I will review some of the most important results in stellar physics of the last few years, and highlight what are the most relevant puzzles that still need to be solved. I will put particular emphasis on the physics of massive stars, which are the progenitors of core-collapse supernovae, gamma-ray bursts and the massive compact remnants observed by LIGO. Dr Cantiello will be based at the Heidelberg Institut fuer Theoretische Studien for his visit to Heidelberg and will be available for meetings by arrangement with his hosts, Fabian Schneider (fabian.schneider@h-its.org), Friedrich Roepke (friedrich.roepke@h-its.org) and Saskia Hekker (saskia.hekker@h-its.org). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Matteo Cantiello (Center for Computational Astrophysics, Flatiron Institute, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
Show/hide abstract
Abstract
Stellar astrophysics is undergoing a renaissance driven by new observational and theoretical capabilities. Wide-field time-domain surveys have uncovered new classes of stellar explosions, helping to understand how stars evolve and end their lives. Gravitational-wave astronomy is providing exciting insights into the properties of the final remnants of massive stars. Asteroseismology, the study of waves in stars, is also producing dramatic breakthroughs in stellar structure and evolution. Thanks to space astrometry, accurate distances are now available for an unprecedented number of galactic stars. From a theoretical standpoint, it is increasingly possible to study aspects of the three-dimensional structure of stars using targeted numerical simulations. These studies can then be used to develop more accurate models of these physics in one-dimensional stellar evolution codes. I will review some of the most important results in stellar physics of the last few years, and highlight what are the most relevant puzzles that still need to be solved. I will put particular emphasis on the physics of massive stars, which are the progenitors of core-collapse supernovae, gamma-ray bursts and the massive compact remnants observed by LIGO. Dr Cantiello will be based at the Heidelberg Institut fuer Theoretische Studien for his visit to Heidelberg and will be available for meetings by arrangement with his hosts, Fabian Schneider (fabian.schneider@h-its.org), Friedrich Roepke (friedrich.roepke@h-its.org) and Saskia Hekker (saskia.hekker@h-its.org). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-07-05
16:00
16:00
A cloud-scale view on the star formation process in nearby galaxies
Dr Eva Schinnerer (MPI Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
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Abstract
Where do stars form and how is their formation regulated across galactic disks are two critical questions for our understanding of the star formation process. High angular observations of nearby galaxies allow us to sample the star formation process across galactic disks reaching now regularly the scales of the star-forming units, namely Giant Molecular Clouds (GMCs) and HII regions. Such data provide new insights on the molecular gas reservoir and its role in the star formation process as well as information on the importance of galactic components such as bulges, stellar bars, spiral arms and active galactic nuclei (AGN) in the conversion of cold (molecular) gas into stars. I will introduce the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) survey and present highlights from the collaboration research. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Eva Schinnerer (MPI Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, main lecture theatre
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Abstract
Where do stars form and how is their formation regulated across galactic disks are two critical questions for our understanding of the star formation process. High angular observations of nearby galaxies allow us to sample the star formation process across galactic disks reaching now regularly the scales of the star-forming units, namely Giant Molecular Clouds (GMCs) and HII regions. Such data provide new insights on the molecular gas reservoir and its role in the star formation process as well as information on the importance of galactic components such as bulges, stellar bars, spiral arms and active galactic nuclei (AGN) in the conversion of cold (molecular) gas into stars. I will introduce the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) survey and present highlights from the collaboration research. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-06-28
16:00
16:00
Turbulent Beginnings: A Predictive Theory of Star Formation in the Interstellar Medium
Prof Blakesley Burkhart (Rutgers University & Flatiron Institute/CCA, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
Our current view of the interstellar medium (ISM) is as a multiphase environment where magnetohydrodynamic (MHD) turbulence affects many key processes: star formation, cosmic ray acceleration, and the evolution of structure in the diffuse ISM. In part 1 of this talk, I shall review the fundamentals of galactic turbulence and discuss progress in developing new techniques for comparing observational data with numerical MHD turbulence simulations. In part 2, I will focus on how turbulence affects the long-standing problem of star formation. From scales of giant molecular clouds (GMCs), I will demonstrate how the star formation efficiency can be analytically calculated from understanding how turbulence, gravity, and stellar feedback induce density fluctuations in the ISM via a probability distribution function analysis. This analytic calculation predicts star formation rates from pc size scales (GMCs) to kpc size scales in galaxies. Prof. Burkhart will be based at the Institut fuer Theoretische Astrophysik for her visit to Heidelberg and will be available for meetings by arrangement with her host, Ralf Klessen (klessen@uni-heidelberg.de).
Prof Blakesley Burkhart (Rutgers University & Flatiron Institute/CCA, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main lecture theatre
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Abstract
Our current view of the interstellar medium (ISM) is as a multiphase environment where magnetohydrodynamic (MHD) turbulence affects many key processes: star formation, cosmic ray acceleration, and the evolution of structure in the diffuse ISM. In part 1 of this talk, I shall review the fundamentals of galactic turbulence and discuss progress in developing new techniques for comparing observational data with numerical MHD turbulence simulations. In part 2, I will focus on how turbulence affects the long-standing problem of star formation. From scales of giant molecular clouds (GMCs), I will demonstrate how the star formation efficiency can be analytically calculated from understanding how turbulence, gravity, and stellar feedback induce density fluctuations in the ISM via a probability distribution function analysis. This analytic calculation predicts star formation rates from pc size scales (GMCs) to kpc size scales in galaxies. Prof. Burkhart will be based at the Institut fuer Theoretische Astrophysik for her visit to Heidelberg and will be available for meetings by arrangement with her host, Ralf Klessen (klessen@uni-heidelberg.de).
2022-06-21
16:00
16:00
Characterising the atmospheres of transiting exoplanets
Dr Thomas Evans (Max-Planck-Institut fuer Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
The observational study of transiting exoplanet atmospheres began in the early 2000s and is flourishing today. I will review the current sample of known exoplanets and the techniques used to characterise their atmospheres. Until now, much of the atmospheric characterisation work has focused on the extreme population of hot Jupiters and I will describe a few notable results. Due to the more challenging nature of the observations, progress has been relatively limited for planets Neptune-sized-and-smaller, but this is set to change as we enter the JWST era. I will preview some of the advances that we are anticipating for the characterisation of rocky planets and sub-Neptunes using this revolutionary facility over the coming years. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Thomas Evans (Max-Planck-Institut fuer Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
The observational study of transiting exoplanet atmospheres began in the early 2000s and is flourishing today. I will review the current sample of known exoplanets and the techniques used to characterise their atmospheres. Until now, much of the atmospheric characterisation work has focused on the extreme population of hot Jupiters and I will describe a few notable results. Due to the more challenging nature of the observations, progress has been relatively limited for planets Neptune-sized-and-smaller, but this is set to change as we enter the JWST era. I will preview some of the advances that we are anticipating for the characterisation of rocky planets and sub-Neptunes using this revolutionary facility over the coming years. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-06-14
16:00
16:00
The Galactic Center: Infrared studies of a unique astrophysical target
Dr Rainer Schoedel (Instituto AstrofÃsica AndalucÃa, Spain)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
The Galactic Center is the only nucleus of a galaxy that we can study on milli-parsec scales. It is also the Milky Way?s most extreme environment and most prolific star forming region. I will review the current state of our knowledge about the structure and formation history of the Galactic Center as well as about the properties and open questions of present day star formation in this nearest analogue of a starburst environment. Dr. Schoedel will be based at the Institut fuer Theoretische Astrophysik for his visit to Heidelberg and will be available for meetings by arrangement with his host, Mattia Sormani (mattia.sormani@uni-heidelberg.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Rainer Schoedel (Instituto AstrofÃsica AndalucÃa, Spain)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
The Galactic Center is the only nucleus of a galaxy that we can study on milli-parsec scales. It is also the Milky Way?s most extreme environment and most prolific star forming region. I will review the current state of our knowledge about the structure and formation history of the Galactic Center as well as about the properties and open questions of present day star formation in this nearest analogue of a starburst environment. Dr. Schoedel will be based at the Institut fuer Theoretische Astrophysik for his visit to Heidelberg and will be available for meetings by arrangement with his host, Mattia Sormani (mattia.sormani@uni-heidelberg.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-05-31
16:00
16:00
Probing the active lives of stars with space missions
Prof. Beate Stelzer (University of Tuebingen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture theatre, Physikalisches Institut, Philosophenweg 12
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Abstract
Magnetic activity is a prime diagnostic for the stellar dynamo and as such an indirect tracer for magnetic fields that are very hard to measure in stars. Studies of the highly energetic and dynamic radiation from the outer atmospheres of late-type stars has received an extra boost during the last few years when its relevance for the evolution of (exo)planets was recognized. In this talk I describe some recent and ongoing multi-wavelength observational projects that address different aspects of stellar activity involving a range of stars from solar-type over the prototypical M dwarf flare stars to the brown dwarf regime. The topics include the relation of activity with stellar rotation and age, the physics of flares, the onset of activity cycles and the effects of stellar activity on potential planets. I also include a brief introduction to the instruments used for these studies, including photometric space missions (Kepler, K2 and TESS) and the latest X-ray survey instrument, eROSITA. Prof. Stelzer will be based at the MPIAstronomie for her visit to Heidelberg and will be available for meetings by arrangement with her host, Wolfgang Brandner (brandner@mpia.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Prof. Beate Stelzer (University of Tuebingen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Main Lecture theatre, Physikalisches Institut, Philosophenweg 12
Show/hide abstract
Abstract
Magnetic activity is a prime diagnostic for the stellar dynamo and as such an indirect tracer for magnetic fields that are very hard to measure in stars. Studies of the highly energetic and dynamic radiation from the outer atmospheres of late-type stars has received an extra boost during the last few years when its relevance for the evolution of (exo)planets was recognized. In this talk I describe some recent and ongoing multi-wavelength observational projects that address different aspects of stellar activity involving a range of stars from solar-type over the prototypical M dwarf flare stars to the brown dwarf regime. The topics include the relation of activity with stellar rotation and age, the physics of flares, the onset of activity cycles and the effects of stellar activity on potential planets. I also include a brief introduction to the instruments used for these studies, including photometric space missions (Kepler, K2 and TESS) and the latest X-ray survey instrument, eROSITA. Prof. Stelzer will be based at the MPIAstronomie for her visit to Heidelberg and will be available for meetings by arrangement with her host, Wolfgang Brandner (brandner@mpia.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-05-24
16:00
16:00
Stellar feedback: from stars to galaxies
Dr Anna McLeod (Centre for Extragalactic Astronomy, Durham University, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
Feedback from massive stars plays a central role in shaping the evolution of galaxies. Conversely, different galactic environments play a central role in regulating the impact of massive stars. Yet, despite a solid qualitative understanding of feedback, our quantitative knowledge about the interdependence of feedback and environment remains poor. Until recently, only a small number of star-forming regions had adequate observational information on both gas and stars needed for detailed stellar feedback studies. Over the past decade, integral field units (IFUs) have revolutionized our approach to resolved stellar feedback studies in nearby galaxies. In this talk I will present recent results of IFU nearby galaxy surveys, showcasing how these can be used to simultaneously characterize the feedback-driven interstellar medium and individual feedback-driving stars up to Mpc distances, and I will discuss how this enables the first empirical quantification of the interdependence between stellar feedback and the environments massive stars form in. Lastly, if there is time, I will also be talking about how IFU data can lead to truly serendipitous discoveries. Dr. McLeod will be based at the Astronomisches Rechen-Institut for her visit to Heidelberg and will be available for meetings by arrangement with her host, Melanie Chevance (chevance@uni-heidelberg.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Dr Anna McLeod (Centre for Extragalactic Astronomy, Durham University, UK)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
Feedback from massive stars plays a central role in shaping the evolution of galaxies. Conversely, different galactic environments play a central role in regulating the impact of massive stars. Yet, despite a solid qualitative understanding of feedback, our quantitative knowledge about the interdependence of feedback and environment remains poor. Until recently, only a small number of star-forming regions had adequate observational information on both gas and stars needed for detailed stellar feedback studies. Over the past decade, integral field units (IFUs) have revolutionized our approach to resolved stellar feedback studies in nearby galaxies. In this talk I will present recent results of IFU nearby galaxy surveys, showcasing how these can be used to simultaneously characterize the feedback-driven interstellar medium and individual feedback-driving stars up to Mpc distances, and I will discuss how this enables the first empirical quantification of the interdependence between stellar feedback and the environments massive stars form in. Lastly, if there is time, I will also be talking about how IFU data can lead to truly serendipitous discoveries. Dr. McLeod will be based at the Astronomisches Rechen-Institut for her visit to Heidelberg and will be available for meetings by arrangement with her host, Melanie Chevance (chevance@uni-heidelberg.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-05-17
16:00
16:00
Galactic Archeaology and Chemical Tagging in the Big Data Era
Prof Keith Hawkins (The University of Texas at Austin, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
What are the processes that govern the formation evolution and assembly of galaxies, like the Milky Way, across cosmic time? This question is among the most fundamental in modern astronomy yet the answer still eludes us to this day. Our Galaxy, our home, The Milky Way, is an optimal laboratory for answering the questions of galaxy formation and assembly because it is one of the only systems to date where we can obtain detailed and precise data on the positions motions and chemical composition for billions of individual stars. In this talk, I will focus on the research I do in Galactic Archaeology, which aims to use the chemical and dynamical information In a vast number of stars in the Galaxy to understand its formation, assembly, and evolution. Specifically, I will focus on the current projects in chemical tagging and the azimuthal variations in metallically distributions of the Galactic disk. Prof. Hawkins will be based at MPIAstronomie for his visit to Heidelberg and will be available for meetings by arrangement with his hosts, Hans-Walter Rix (rix@mpia.de) and Eduardo Banados (banados@mpia.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
Prof Keith Hawkins (The University of Texas at Austin, USA)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
Show/hide abstract
Abstract
What are the processes that govern the formation evolution and assembly of galaxies, like the Milky Way, across cosmic time? This question is among the most fundamental in modern astronomy yet the answer still eludes us to this day. Our Galaxy, our home, The Milky Way, is an optimal laboratory for answering the questions of galaxy formation and assembly because it is one of the only systems to date where we can obtain detailed and precise data on the positions motions and chemical composition for billions of individual stars. In this talk, I will focus on the research I do in Galactic Archaeology, which aims to use the chemical and dynamical information In a vast number of stars in the Galaxy to understand its formation, assembly, and evolution. Specifically, I will focus on the current projects in chemical tagging and the azimuthal variations in metallically distributions of the Galactic disk. Prof. Hawkins will be based at MPIAstronomie for his visit to Heidelberg and will be available for meetings by arrangement with his hosts, Hans-Walter Rix (rix@mpia.de) and Eduardo Banados (banados@mpia.de). Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09
2022-05-10
16:00
16:00
Testing cosmological fields with Gravitational Waves
Prof. Lavinia Heisenberg (ITP, Heidelberg University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
After introducing the standard model of cosmology and its fundamental pillars, I will discuss its successes and problems. Based on these I will analyze the fundamental assumptions of the underlying model and how one can consistently try to extend/generalize them. I will then discuss how we can use cosmological and astrophysical observations to test gravity and our fundamental assumptions, with a special emphasis on gravitational waves measurements and the future ahead. Anybody unable to attend the colloquium in person is invited to participate by Zoom through the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 (Meeting ID: 942 0262 2849 Passcode: 792771)
Prof. Lavinia Heisenberg (ITP, Heidelberg University)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
After introducing the standard model of cosmology and its fundamental pillars, I will discuss its successes and problems. Based on these I will analyze the fundamental assumptions of the underlying model and how one can consistently try to extend/generalize them. I will then discuss how we can use cosmological and astrophysical observations to test gravity and our fundamental assumptions, with a special emphasis on gravitational waves measurements and the future ahead. Anybody unable to attend the colloquium in person is invited to participate by Zoom through the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 (Meeting ID: 942 0262 2849 Passcode: 792771)
2022-05-03
16:00
16:00
eROSITA on SRG: Mapping the Hot Universe
Dr Andrea Merloni (MPI Extraterrestrische Physik, Garching)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
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Abstract
The next generation of wide-area, sensitive X-ray surveys designed to map the hot and energetic Universe has arrived, thanks to eROSITA (extended ROentgen Survey with an Imaging Telescope Array), the core instrument on the Russian-German Spektrum-Roentgen-Gamma (SRG) mission. eROSITA high sensitivity, large field of view, high spatial resolution and survey efficiency is bound to revolutionise X-ray astronomy and deliver large legacy samples for many classes of astronomical objects in the energy range 0.2-8 keV. Over this energy range, telescopes are sensitive to the emission of millions of degrees hot gas, revealing, among others, the most massive collapsed structures of the Universe (clusters and groups of galaxies), the hot ISM of the Milky Way and the Supernova remnants that energise it, the atmospheres of neutron stars, the magnetic coronae of accretion discs around black holes. I will present an overview of the instrument capabilities, the current status of the mission, a few selected early science results and the expectations for the survey program, which has completed last December the fourth of its eight planned charts of the whole sky. Dr. Merloni will be visiting Heidelberg on Tuesday and Wednesday 3rd & 4th May and is available for meetings by arrangement through Richard Tuffs (Richard.Tuffs@mpi-hd.mpg.de).
Dr Andrea Merloni (MPI Extraterrestrische Physik, Garching)
Heidelberg Joint Astronomical Colloquium
Physikalisches Institut, Philosophenweg 12, Main Lecture Theatre
Show/hide abstract
Abstract
The next generation of wide-area, sensitive X-ray surveys designed to map the hot and energetic Universe has arrived, thanks to eROSITA (extended ROentgen Survey with an Imaging Telescope Array), the core instrument on the Russian-German Spektrum-Roentgen-Gamma (SRG) mission. eROSITA high sensitivity, large field of view, high spatial resolution and survey efficiency is bound to revolutionise X-ray astronomy and deliver large legacy samples for many classes of astronomical objects in the energy range 0.2-8 keV. Over this energy range, telescopes are sensitive to the emission of millions of degrees hot gas, revealing, among others, the most massive collapsed structures of the Universe (clusters and groups of galaxies), the hot ISM of the Milky Way and the Supernova remnants that energise it, the atmospheres of neutron stars, the magnetic coronae of accretion discs around black holes. I will present an overview of the instrument capabilities, the current status of the mission, a few selected early science results and the expectations for the survey program, which has completed last December the fourth of its eight planned charts of the whole sky. Dr. Merloni will be visiting Heidelberg on Tuesday and Wednesday 3rd & 4th May and is available for meetings by arrangement through Richard Tuffs (Richard.Tuffs@mpi-hd.mpg.de).
2022-02-15
16:00
16:00
The Physics and Astrophysics of Extreme Particle Accelerators
Prof. Felix Aharonian (Max-Planck-Institut fuer Kernphysik, Heidelberg and Dublin Institute for Advanced Studies)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
The origin of Cosmic Rays (CR), more than 100 years after their discovery, is still considered a "century-old mystery". The reason for such a pessimistic assessment is that we do not know yet, despite the recent remarkable advances in CR studies, which source population(s) contribute to CR fluxes measured in the Earth's vicinity (local "CR fog"). Identifying the contributors to the local CR flux with known astronomical source populations is one of the highest priorities of the field. However, the CR studies cannot be reduced merely to this objective. The term "cosmic rays" has broader implications. After matter, radiation and magnetic fields, these relativistic particles constitute the fourth substance of the observable Universe. The localization, identification and exploration of physical conditions and processes in these CR factories, independent of their relative contributions to the "CR fog", is a fundamental issue in its own right. In this context, the Extreme Accelerators - perfectly designed by Nature machines accelerating particles with a rate close to the theoretical margin, in general, and their subclass, the so-called Galactic PeVatrons, in particular, are of special interest. I will discuss the recent progress in this area thanks to the (surprise) discovery of a large number of electron and proton PeVatrons in the Milky Way. Zoom link https://zoom.us/j/95485119455?pwd=WkhxWkNDVlhBcER4TTU2M001aEw0UT09
Prof. Felix Aharonian (Max-Planck-Institut fuer Kernphysik, Heidelberg and Dublin Institute for Advanced Studies)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
The origin of Cosmic Rays (CR), more than 100 years after their discovery, is still considered a "century-old mystery". The reason for such a pessimistic assessment is that we do not know yet, despite the recent remarkable advances in CR studies, which source population(s) contribute to CR fluxes measured in the Earth's vicinity (local "CR fog"). Identifying the contributors to the local CR flux with known astronomical source populations is one of the highest priorities of the field. However, the CR studies cannot be reduced merely to this objective. The term "cosmic rays" has broader implications. After matter, radiation and magnetic fields, these relativistic particles constitute the fourth substance of the observable Universe. The localization, identification and exploration of physical conditions and processes in these CR factories, independent of their relative contributions to the "CR fog", is a fundamental issue in its own right. In this context, the Extreme Accelerators - perfectly designed by Nature machines accelerating particles with a rate close to the theoretical margin, in general, and their subclass, the so-called Galactic PeVatrons, in particular, are of special interest. I will discuss the recent progress in this area thanks to the (surprise) discovery of a large number of electron and proton PeVatrons in the Milky Way. Zoom link https://zoom.us/j/95485119455?pwd=WkhxWkNDVlhBcER4TTU2M001aEw0UT09
2022-02-08
16:00
16:00
Barred galaxies in LambdaCDM: Deciphering the formation history and dark matter content of Milky Way-type galaxies
Dr. Francesca Fragkoudi (European Southern Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
The advent of high resolution hydrodynamical cosmological simulations allows us to now study the dynamics of barred galaxies, such as our own Milky Way, within the full ?CDM cosmological context. I will present what we have learned about the formation history of our galaxy and its inner structures -- such as the bar and the boxy/peanut bulge -- by comparing the chemo-dynamical properties of its inner stellar populations to both isolated/tailored and cosmological simulations. In particular, I will present evidence of the Galaxy's unusually quiescent merger history, and of the almost entirely in-situ formation of its bulge. I will also show how studying the dynamics of barred galaxies in cosmological simulations -- in particular the interaction through dynamical friction of the bar and the dark matter halo -- can help us shed light on the amount of dark matter in massive spiral galaxies. I will discuss these results in light of recent claims in the literature of a 10sigma tension between fast bars and LCDM, and within the context of galaxy formation and evolution in general. The Zoom session for this colloquium will be open-ended to allow further informal discussions, moderated by Dr Fragkoudi's host, Dr Nadine Neumayer (neumayer@mpia.de). zoom access code 69120
Dr. Francesca Fragkoudi (European Southern Observatory)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
The advent of high resolution hydrodynamical cosmological simulations allows us to now study the dynamics of barred galaxies, such as our own Milky Way, within the full ?CDM cosmological context. I will present what we have learned about the formation history of our galaxy and its inner structures -- such as the bar and the boxy/peanut bulge -- by comparing the chemo-dynamical properties of its inner stellar populations to both isolated/tailored and cosmological simulations. In particular, I will present evidence of the Galaxy's unusually quiescent merger history, and of the almost entirely in-situ formation of its bulge. I will also show how studying the dynamics of barred galaxies in cosmological simulations -- in particular the interaction through dynamical friction of the bar and the dark matter halo -- can help us shed light on the amount of dark matter in massive spiral galaxies. I will discuss these results in light of recent claims in the literature of a 10sigma tension between fast bars and LCDM, and within the context of galaxy formation and evolution in general. The Zoom session for this colloquium will be open-ended to allow further informal discussions, moderated by Dr Fragkoudi's host, Dr Nadine Neumayer (neumayer@mpia.de). zoom access code 69120
2022-02-01
16:00
16:00
Unveiling the early stages of planet formation
Dr. Myriam Benisty (Institute for Planetary sciences and Astrophysics, Grenoble, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
Recent observing campaigns have revealed a great diversity in exoplanetary systems whose origin is yet to be understood. How and when planets form, and how they evolve and interact with their birth environment, the protoplanetary disks, are major open questions. Protoplanetary disks evolve and dissipate rapidly while planets are forming, implying a direct feedback between the processes of planet formation and disk evolution. These mechanisms leave clear imprints on the disk structure that can be directly observed. In the past few years, high-resolution observations of protoplanetary disks obtained in the infrared and in the millimeter regime have shown that small scale structures are ubiquitous in protoplanetary disks, and could result from the dynamical interaction with embedded planets. I will present recent observational results on protoplanetary disks, that allow to probe the disk structure and the dynamics of solids, and in particular, in the so far unique system that hosts two directly imaged protoplanets, PDS70. The Zoom session for this colloquium will be open-ended to allow further informal discussions, moderated by Dr Benisty's host, Professor Dullemond (dullemond@uni-heidelberg.de). zoom access code 69120
Dr. Myriam Benisty (Institute for Planetary sciences and Astrophysics, Grenoble, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
Recent observing campaigns have revealed a great diversity in exoplanetary systems whose origin is yet to be understood. How and when planets form, and how they evolve and interact with their birth environment, the protoplanetary disks, are major open questions. Protoplanetary disks evolve and dissipate rapidly while planets are forming, implying a direct feedback between the processes of planet formation and disk evolution. These mechanisms leave clear imprints on the disk structure that can be directly observed. In the past few years, high-resolution observations of protoplanetary disks obtained in the infrared and in the millimeter regime have shown that small scale structures are ubiquitous in protoplanetary disks, and could result from the dynamical interaction with embedded planets. I will present recent observational results on protoplanetary disks, that allow to probe the disk structure and the dynamics of solids, and in particular, in the so far unique system that hosts two directly imaged protoplanets, PDS70. The Zoom session for this colloquium will be open-ended to allow further informal discussions, moderated by Dr Benisty's host, Professor Dullemond (dullemond@uni-heidelberg.de). zoom access code 69120
2022-01-25
16:00
16:00
The assembly history and evolution of the Milky Way as seen through the lens of asteroseismic ages
Prof. Andrea Miglio (University of Bologna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
Our understanding of the formation and evolution of the Milky Way is often blurred and biased by the lack of precise and accurate stellar ages. In this contribution I will present the ongoing efforts and recent results of the asterochronometry project (https://asterochronometry.eu/ [asterochronometry.eu]), which aims both at testing and improving our knowledge of stellar physics, and at determining precise and accurate ages of stars (to 10-15%) in the regions of the Galaxy sampled by Kepler, K2, CoRoT, and TESS. Examples of recent and ongoing work will include age-dating stars using data from the TESS mission and inferences on the ages of both Gaia-Enceladus and in-situ stars observed by Kepler. Finally, I will discuss the prospects for extending these studies to larger samples, and briefly present the science case for a future mission dedicated to asteroseismology of crowded fields. The Zoom session for this colloquium will be open-ended to allow further informal discussions, moderated by Prof. Miglio's host, Hans-Guenther Ludwig (hludwig@lsw.uni-heidelberg.de). zoom access code 69120
Prof. Andrea Miglio (University of Bologna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
Our understanding of the formation and evolution of the Milky Way is often blurred and biased by the lack of precise and accurate stellar ages. In this contribution I will present the ongoing efforts and recent results of the asterochronometry project (https://asterochronometry.eu/ [asterochronometry.eu]), which aims both at testing and improving our knowledge of stellar physics, and at determining precise and accurate ages of stars (to 10-15%) in the regions of the Galaxy sampled by Kepler, K2, CoRoT, and TESS. Examples of recent and ongoing work will include age-dating stars using data from the TESS mission and inferences on the ages of both Gaia-Enceladus and in-situ stars observed by Kepler. Finally, I will discuss the prospects for extending these studies to larger samples, and briefly present the science case for a future mission dedicated to asteroseismology of crowded fields. The Zoom session for this colloquium will be open-ended to allow further informal discussions, moderated by Prof. Miglio's host, Hans-Guenther Ludwig (hludwig@lsw.uni-heidelberg.de). zoom access code 69120
2022-01-18
16:00
16:00
Black Holes - Nature or Nurture?
Prof. Roger Blandford (Stanford University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
Black holes power many of the most powerful sources in the universe through their disks, jets and winds. This power derives from their rotational energy (Nature) and the gravitational energy released by accreting gas (Nurture). The balance of these two modes and their implications, will be re-examined in the light of recent, remarkable observations of the nearby galaxy M87 by the Event Horizon Telescope. Implications for other sources will be discussed. Professor Blandford is hosted by Dr. Brian Reville (brian.reville@mpi-hd.mpg.de)
Prof. Roger Blandford (Stanford University, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
Black holes power many of the most powerful sources in the universe through their disks, jets and winds. This power derives from their rotational energy (Nature) and the gravitational energy released by accreting gas (Nurture). The balance of these two modes and their implications, will be re-examined in the light of recent, remarkable observations of the nearby galaxy M87 by the Event Horizon Telescope. Implications for other sources will be discussed. Professor Blandford is hosted by Dr. Brian Reville (brian.reville@mpi-hd.mpg.de)
2022-01-11
16:00
16:00
Stellar Interactions & Transients
Dr. Silvia Toonen (University of Amsterdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
The advent and development of large-scale time domain surveys are revealing the existence of a large and diverse zoo of transients; common transients that can be used as tools to constrain GR or cosmological parameters, and rare & exotic transients that are observed for the first time. The origin of the transients is often unknown, but linked to stellar systems and interactions. In this talk I will show novel channels to induce stellar interactions and subsequent transients -in electromagnetic radiation as well as gravitational waves, ranging from stellar mergers to gravitational wave sources. Amongst others I will discuss the potential of triple stars as GW progenitors: while triple star systems are common (even more common than binaries for massive stars!), our understanding of their evolution has lagged behind compared to single and binary stars. Dr. Toonen will be hosted by Fabian Schneider (fabian.schneider@h-its.org)
Dr. Silvia Toonen (University of Amsterdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
The advent and development of large-scale time domain surveys are revealing the existence of a large and diverse zoo of transients; common transients that can be used as tools to constrain GR or cosmological parameters, and rare & exotic transients that are observed for the first time. The origin of the transients is often unknown, but linked to stellar systems and interactions. In this talk I will show novel channels to induce stellar interactions and subsequent transients -in electromagnetic radiation as well as gravitational waves, ranging from stellar mergers to gravitational wave sources. Amongst others I will discuss the potential of triple stars as GW progenitors: while triple star systems are common (even more common than binaries for massive stars!), our understanding of their evolution has lagged behind compared to single and binary stars. Dr. Toonen will be hosted by Fabian Schneider (fabian.schneider@h-its.org)
2021-12-21
16:00
16:00
The assembly history and evolution of the Milky Way as seen through the lens of asteroseismic ages
Prof. Andrea Miglio (University of Bologna)
Heidelberg Joint Astronomical Colloquium
Zoom, Zoom
Show/hide abstract
Abstract
Please note: this colloquium has been postponed until 25th January 2022 due to illness Our understanding of the formation and evolution of the Milky Way is often blurred and biased by the lack of precise and accurate stellar ages. In this contribution I will present the ongoing efforts and recent results of the asterochronometry project (https://asterochronometry.eu/ [asterochronometry.eu]), which aims both at testing and improving our knowledge of stellar physics, and at determining precise and accurate ages of stars (to 10-15%) in the regions of the Galaxy sampled by Kepler, K2, CoRoT, and TESS. Examples of recent and ongoing work will include age-dating stars using data from the TESS mission and inferences on the ages of both Gaia-Enceladus and in-situ stars observed by Kepler. Finally, I will discuss the prospects for extending these studies to larger samples, and briefly present the science case for a future mission dedicated to asteroseismology of crowded fields. Prof. Miglio is hosted by Ralf Klessen (klessen@uni-heidelberg.de). zoom access code 69120
Prof. Andrea Miglio (University of Bologna)
Heidelberg Joint Astronomical Colloquium
Zoom, Zoom
Show/hide abstract
Abstract
Please note: this colloquium has been postponed until 25th January 2022 due to illness Our understanding of the formation and evolution of the Milky Way is often blurred and biased by the lack of precise and accurate stellar ages. In this contribution I will present the ongoing efforts and recent results of the asterochronometry project (https://asterochronometry.eu/ [asterochronometry.eu]), which aims both at testing and improving our knowledge of stellar physics, and at determining precise and accurate ages of stars (to 10-15%) in the regions of the Galaxy sampled by Kepler, K2, CoRoT, and TESS. Examples of recent and ongoing work will include age-dating stars using data from the TESS mission and inferences on the ages of both Gaia-Enceladus and in-situ stars observed by Kepler. Finally, I will discuss the prospects for extending these studies to larger samples, and briefly present the science case for a future mission dedicated to asteroseismology of crowded fields. Prof. Miglio is hosted by Ralf Klessen (klessen@uni-heidelberg.de). zoom access code 69120
2021-12-14
16:00
16:00
Weaving the Milky Way tapestry
Dr. Ana Bonaca (Carnegie Observatories, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
Explorations of our galaxy, the Milky Way, are currently undergoing a revolution. Spearheaded by Gaia, large missions are measuring the motions, chemical compositions, and ages of stars more precisely and farther than ever before. Using these data, for the first time we have been able to unambiguously isolate stars born in smaller galaxies that have been assimilated by the Milky Way throughout its history. Yet open questions abound following this milestone achievement: "How are the different progenitors of the Milky Way related?" "How has their arrival impacted the stars and dark matter already in the Milky Way?" I will discuss how the answers to these questions can be gleaned from precise orbital histories of stars in the Milky Way halo, and what they imply for the intertwined quests to understand the physics of galaxy formation and the nature of dark matter. Dr. Bonaca is visiting Heidelberg in the week of the colloquium, and can be contacted through her host, Diederik Kruijssen (kruijssen@uni-heidelberg.de). zoom access code 69120
Dr. Ana Bonaca (Carnegie Observatories, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
Explorations of our galaxy, the Milky Way, are currently undergoing a revolution. Spearheaded by Gaia, large missions are measuring the motions, chemical compositions, and ages of stars more precisely and farther than ever before. Using these data, for the first time we have been able to unambiguously isolate stars born in smaller galaxies that have been assimilated by the Milky Way throughout its history. Yet open questions abound following this milestone achievement: "How are the different progenitors of the Milky Way related?" "How has their arrival impacted the stars and dark matter already in the Milky Way?" I will discuss how the answers to these questions can be gleaned from precise orbital histories of stars in the Milky Way halo, and what they imply for the intertwined quests to understand the physics of galaxy formation and the nature of dark matter. Dr. Bonaca is visiting Heidelberg in the week of the colloquium, and can be contacted through her host, Diederik Kruijssen (kruijssen@uni-heidelberg.de). zoom access code 69120
2021-12-07
16:00
16:00
Ten months of Perseverance on Mars
Prof. Kenneth Farley (California Institute of Technology & Jet Propulsion Laboratory, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
The Perseverance rover landed on Mars on February 18, 2021 on the floor of a crater that held a deep lake about 3.5 billion years ago. The mission's goals are to interpret the rocks deposited on the crater floor, seek evidence of possible ancient life recorded in those rocks, and prepare a collection of rock samples for possible return to Earth by future missions. I am Project Scientist for the mission, and in this talk I'll explain this mission's motivations, activities, and discoveries in its first nine months.
Prof. Kenneth Farley (California Institute of Technology & Jet Propulsion Laboratory, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
The Perseverance rover landed on Mars on February 18, 2021 on the floor of a crater that held a deep lake about 3.5 billion years ago. The mission's goals are to interpret the rocks deposited on the crater floor, seek evidence of possible ancient life recorded in those rocks, and prepare a collection of rock samples for possible return to Earth by future missions. I am Project Scientist for the mission, and in this talk I'll explain this mission's motivations, activities, and discoveries in its first nine months.
2021-11-30
16:00
16:00
Gas dynamics, inflow and star formation in the innermost 3 kpc of the Milky Way
Dr Mattia Sormani (ITA/ZAH, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
I will give an introduction to gas dynamics and star formation in the central region (R<3kpc) of the Milky Way. This region is dominated by the strongly non-axisymmetric gravitational potential of the Galactic bar. After reviewing the basic theoretical tools, I will discuss several topics including (i) how to interpret the observed longitude-velocity maps of CO, HI and other interstellar gas tracers; (ii) how we can use the gas dynamics to constrain the properties of the Galactic bar; (iii) how the gas is driven inwards from the Galactic disc (R~3kpc) down to the Central Molecular Zone (CMZ, R~120pc) and then to the central black hole SgrA*; (iv) the spatial and temporal distribution of star formation in the Galactic centre. Finally, I will highlight some open questions and directions of future research.
Dr Mattia Sormani (ITA/ZAH, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
Show/hide abstract
Abstract
I will give an introduction to gas dynamics and star formation in the central region (R<3kpc) of the Milky Way. This region is dominated by the strongly non-axisymmetric gravitational potential of the Galactic bar. After reviewing the basic theoretical tools, I will discuss several topics including (i) how to interpret the observed longitude-velocity maps of CO, HI and other interstellar gas tracers; (ii) how we can use the gas dynamics to constrain the properties of the Galactic bar; (iii) how the gas is driven inwards from the Galactic disc (R~3kpc) down to the Central Molecular Zone (CMZ, R~120pc) and then to the central black hole SgrA*; (iv) the spatial and temporal distribution of star formation in the Galactic centre. Finally, I will highlight some open questions and directions of future research.
2021-11-23
16:00
16:00
The Chiral Puzzle of Life
Dr. Noemie Globus (University of California, Santa Cruz & University of Prague)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
While we have not yet reached a consensus on the definition of life, biological homochirality seems to be a necessary step for life?s emergence. The unraveling of its origin requires interdisciplinary research, by exploring each of fundamental physics, modern chemistry, astrophysics, and biology. In this talk, I will focus on the origin of biological homochirality in the context of astrophysics and particle physics. The weak force, one of the fundamental forces operating in nature, is parity-violating, and has been implicated in biological homochirality since over half a century. On Earth, at ground level, most of our cosmic radiation dose comes from polarized muons formed in a decay involving the weak force. Recent ideas connecting the chirality of cosmic muons to a chiral bias in biological processes, and possible routes to detect chirality in astrophysical environments will be discussed. Dr. Globus is hosted by Dr. Christian Fendt, MPIA (fendt@mpia-hd.mpg.de)
Dr. Noemie Globus (University of California, Santa Cruz & University of Prague)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
While we have not yet reached a consensus on the definition of life, biological homochirality seems to be a necessary step for life?s emergence. The unraveling of its origin requires interdisciplinary research, by exploring each of fundamental physics, modern chemistry, astrophysics, and biology. In this talk, I will focus on the origin of biological homochirality in the context of astrophysics and particle physics. The weak force, one of the fundamental forces operating in nature, is parity-violating, and has been implicated in biological homochirality since over half a century. On Earth, at ground level, most of our cosmic radiation dose comes from polarized muons formed in a decay involving the weak force. Recent ideas connecting the chirality of cosmic muons to a chiral bias in biological processes, and possible routes to detect chirality in astrophysical environments will be discussed. Dr. Globus is hosted by Dr. Christian Fendt, MPIA (fendt@mpia-hd.mpg.de)
2021-11-16
16:00
16:00
Do Habitable Worlds Require Magnetic Fields?
Prof. David Brain (University of Colorado, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
If Earth lost its magnetic field, would its ability to support life be diminished? If Mars had retained a strong magnetic field, would it be habitable today? For decades it was assumed that the answers to these two questions were "yes". In recent years, however, the canonical assumption that planetary magnetic fields improve planetary habitability has been called into question. This presentation will review the perceived connections between magnetic fields and surface and atmospheric habitability of planets and discuss several approaches to resolving this important question: (1) intercomparison of observations of Venus, Earth, and Mars, (2) analysis of observations from unmagnetized and magnetized regions of Mars, and (3) development of large computer simulations for the interaction of a star with a planet?s atmosphere and magnetic field. In the end, all approaches are likely to be necessary. We will discuss an ongoing team science effort named MACH that draws on expertise from the heliophysics, planetary, and exoplanetary communities. Prof. Brain is hosted by Dr. Karan Molaverdikhani (karan@lsw.uni-heidelberg.de).
Prof. David Brain (University of Colorado, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
If Earth lost its magnetic field, would its ability to support life be diminished? If Mars had retained a strong magnetic field, would it be habitable today? For decades it was assumed that the answers to these two questions were "yes". In recent years, however, the canonical assumption that planetary magnetic fields improve planetary habitability has been called into question. This presentation will review the perceived connections between magnetic fields and surface and atmospheric habitability of planets and discuss several approaches to resolving this important question: (1) intercomparison of observations of Venus, Earth, and Mars, (2) analysis of observations from unmagnetized and magnetized regions of Mars, and (3) development of large computer simulations for the interaction of a star with a planet?s atmosphere and magnetic field. In the end, all approaches are likely to be necessary. We will discuss an ongoing team science effort named MACH that draws on expertise from the heliophysics, planetary, and exoplanetary communities. Prof. Brain is hosted by Dr. Karan Molaverdikhani (karan@lsw.uni-heidelberg.de).
2021-11-09
16:00
16:00
The birth of the first massive galaxies and black holes
Dr. Eduardo Banados (Max-Planck-Institut fuer Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
We are the first generation of human beings able to directly observe and study the cosmic era when the first galaxies and black holes formed. Quasars are among the most luminous sources known and can be studied in detail even during the first billion years of the Universe (at redshifts z>6). I will summarize my team efforts to search for and characterize the most distant quasars. This has led to the discovery of the largest number of bright quasars at z>6, including the most distant radio-source known at z~7, and the three most distant quasars known at z>7.5. These distant quasars provide important clues about the build-up of the first massive galaxies and black holes, as well as the epoch of reionization. I will review the diverse range of physical properties of these quasars on different scales, including follow-up studies from X-rays to radio wavelengths.
Dr. Eduardo Banados (Max-Planck-Institut fuer Astronomie, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
We are the first generation of human beings able to directly observe and study the cosmic era when the first galaxies and black holes formed. Quasars are among the most luminous sources known and can be studied in detail even during the first billion years of the Universe (at redshifts z>6). I will summarize my team efforts to search for and characterize the most distant quasars. This has led to the discovery of the largest number of bright quasars at z>6, including the most distant radio-source known at z~7, and the three most distant quasars known at z>7.5. These distant quasars provide important clues about the build-up of the first massive galaxies and black holes, as well as the epoch of reionization. I will review the diverse range of physical properties of these quasars on different scales, including follow-up studies from X-rays to radio wavelengths.
2021-11-02
16:00
16:00
Multi-messenger Astronomy with high-energy Neutrinos
Prof. Anna Franckowiak (Astronomisches Institut, University of Bochum)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
Cosmic rays are charged particles (mainly protons) that bombard the Earth from all directions reaching energies up to 10 million times what can be archived by the most powerful man-made accelerator, the LHC. Their origin is difficult to trace, because cosmic rays are deflected by magnetic fields on their journey from their source to Earth. However, cosmic rays produce gamma-ray photons and neutrinos in interactions with matter and photon fields in or close to their source. Being neutral those secondary particles can travel undeflected and ultimately point back to the source. While gamma rays are not solely produced in interactions of cosmic ray protons, neutrinos provide a smoking-gun signature for acceleration of protons (or heavier nuclei). A diffuse flux of cosmic neutrinos was first discovered by the cubic-kilometer-sized IceCube detector located at the South Pole in 2013. I will present the ongoing search for the origin of those neutrinos using multi-messenger studies and discuss promising candidate sources including the gamma ray blazar TXS 0506+056, the tidal disruption event AT2019dsg and the nearby Seyfert galaxy NGC 1068.
Prof. Anna Franckowiak (Astronomisches Institut, University of Bochum)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
Cosmic rays are charged particles (mainly protons) that bombard the Earth from all directions reaching energies up to 10 million times what can be archived by the most powerful man-made accelerator, the LHC. Their origin is difficult to trace, because cosmic rays are deflected by magnetic fields on their journey from their source to Earth. However, cosmic rays produce gamma-ray photons and neutrinos in interactions with matter and photon fields in or close to their source. Being neutral those secondary particles can travel undeflected and ultimately point back to the source. While gamma rays are not solely produced in interactions of cosmic ray protons, neutrinos provide a smoking-gun signature for acceleration of protons (or heavier nuclei). A diffuse flux of cosmic neutrinos was first discovered by the cubic-kilometer-sized IceCube detector located at the South Pole in 2013. I will present the ongoing search for the origin of those neutrinos using multi-messenger studies and discuss promising candidate sources including the gamma ray blazar TXS 0506+056, the tidal disruption event AT2019dsg and the nearby Seyfert galaxy NGC 1068.
2021-07-20
16:00
16:00
LHAASO and it's First Few Discoveries
Prof. Zhen Cao (Institute for High Energy Physics, Beijing, China)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The Large High Altitude Air Shower Observatory (LHAASO) is a new ground-based Gamma Ray detector array in its final stages of construction. The 3/4 array has been in operation for months. Many VHE gamma ray sources have been detected, including well known sources such as the Crab and Mkr421. Since many sources have been found with strong emission in the UHE(> 0.1 PeV) band, LHAASO is also starting a new era of UHE gamma ray astronomy. Due to LHAASO’s unprecedented sensitivity at photon energies above 10 TeV and it’s extremely high background rejection capability, super-PeV gamma-like events, including a record-breaking event with 1.4 PeV, are being detected for the first time. The SEDs of several galactic gamma-ray sources above 0.1 PeV measured by LHAASO reveal that our galaxy is full of PeVatrons. The extreme features of the electron PeVatron inside the Crab pose strong challenges to models and fundamental theory. These exciting discoveries enable and guide a search for hadronic PeVatrons where cosmic rays originate. With the operation of the full scale LHAASO array now starting, further exciting observational results, including those probing charged cosmic rays in the “knee” region of the energy spectrum of cosmic rays, are anticipated. Prof. Cao’s host is Felix Aharonian (felix.aharonian@mpi-hd.mpg.de)
Prof. Zhen Cao (Institute for High Energy Physics, Beijing, China)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The Large High Altitude Air Shower Observatory (LHAASO) is a new ground-based Gamma Ray detector array in its final stages of construction. The 3/4 array has been in operation for months. Many VHE gamma ray sources have been detected, including well known sources such as the Crab and Mkr421. Since many sources have been found with strong emission in the UHE(> 0.1 PeV) band, LHAASO is also starting a new era of UHE gamma ray astronomy. Due to LHAASO’s unprecedented sensitivity at photon energies above 10 TeV and it’s extremely high background rejection capability, super-PeV gamma-like events, including a record-breaking event with 1.4 PeV, are being detected for the first time. The SEDs of several galactic gamma-ray sources above 0.1 PeV measured by LHAASO reveal that our galaxy is full of PeVatrons. The extreme features of the electron PeVatron inside the Crab pose strong challenges to models and fundamental theory. These exciting discoveries enable and guide a search for hadronic PeVatrons where cosmic rays originate. With the operation of the full scale LHAASO array now starting, further exciting observational results, including those probing charged cosmic rays in the “knee” region of the energy spectrum of cosmic rays, are anticipated. Prof. Cao’s host is Felix Aharonian (felix.aharonian@mpi-hd.mpg.de)
2021-07-13
16:00
16:00
The Genesis of the First Elements
Dr. Ryan Cooke (University of Durham)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 We are currently in an exciting era of precision cosmology. With the release of the cosmic microwave background data recorded by the Planck satellite, we are now in a position to accurately test the Standard Model of cosmology and particle physics. In this talk, I will present the latest results from a survey to discover and characterize some of the most metal-poor, gas-rich galaxies currently known. These near-pristine environments allow us to study the early phases of dwarf galaxy evolution, probe the chemical signatures of the first stars, and study the primordial abundances of the light elements. I will present some of the key results from this survey. Dr Cooke is hosted by Dr. Diederik Kruijssen (kruijssen@uni-heidelberg.de)
Dr. Ryan Cooke (University of Durham)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 We are currently in an exciting era of precision cosmology. With the release of the cosmic microwave background data recorded by the Planck satellite, we are now in a position to accurately test the Standard Model of cosmology and particle physics. In this talk, I will present the latest results from a survey to discover and characterize some of the most metal-poor, gas-rich galaxies currently known. These near-pristine environments allow us to study the early phases of dwarf galaxy evolution, probe the chemical signatures of the first stars, and study the primordial abundances of the light elements. I will present some of the key results from this survey. Dr Cooke is hosted by Dr. Diederik Kruijssen (kruijssen@uni-heidelberg.de)
2021-07-06
16:00
16:00
Mapping the Ionized ISM in Nearby Galaxies
Dr. Kathryn Kreckel (ZAH, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The ionized interstellar medium (ISM) provides crucial insights into understanding baryon cycling within disk galaxies and tracing radiative and mechanical feedback from young massive stars. With new VLT/MUSE optical integral field spectroscopy, the PHANGS team now has a wealth of emission line maps that trace different ionization sources and physical conditions across 19 nearby disk galaxies at the 50pc spatial scales needed to isolate individual ionized regions (e.g. HII regions, supernova remnants, planetary nebulae) from surrounding diffuse ionized gas. Together with dedicated HST and ALMA observations, providing characterization of the young star clusters and giant molecular clouds, we can now explore a comprehensive view of the chemo-dynamical evolution of the star formation process across different environments. I will present our most recent results measuring the gas phase oxygen abundances across thousands of HII regions, and quantifying the mixing and feedback processes that we observe. Within the context of the large scale galactic environment, these studies have implications for our understanding of how spiral structure acts to organize and mix the ISM, and regulate star formation.
Dr. Kathryn Kreckel (ZAH, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The ionized interstellar medium (ISM) provides crucial insights into understanding baryon cycling within disk galaxies and tracing radiative and mechanical feedback from young massive stars. With new VLT/MUSE optical integral field spectroscopy, the PHANGS team now has a wealth of emission line maps that trace different ionization sources and physical conditions across 19 nearby disk galaxies at the 50pc spatial scales needed to isolate individual ionized regions (e.g. HII regions, supernova remnants, planetary nebulae) from surrounding diffuse ionized gas. Together with dedicated HST and ALMA observations, providing characterization of the young star clusters and giant molecular clouds, we can now explore a comprehensive view of the chemo-dynamical evolution of the star formation process across different environments. I will present our most recent results measuring the gas phase oxygen abundances across thousands of HII regions, and quantifying the mixing and feedback processes that we observe. Within the context of the large scale galactic environment, these studies have implications for our understanding of how spiral structure acts to organize and mix the ISM, and regulate star formation.
2021-06-22
16:00
16:00
A new era of Interferometry with GRAVITY(+)
Dr. Frank Eisenhauer (MPI fuer Extraterrestrische Physik)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The GRAVITY instrument has enabled major steps forward in infrared interferometry, by phase-referenced imaging at milli-arcsecond resolution, with a sensitivity increase by factor thousands, 30-100 micro-arcsecond astrometry, and few micro-arcsecond differential spectro-astrometry. We give an overview of the technology behind GRAVITY and highlight the game-changing results from the first three years of operation. Our presentation takes us from nearby exoplanets all the way to distant quasars, with special focus on the Galactic Center, the first precision tests of Einstein?s theory of General Relativity around massive black holes, and tests of the massive black hole paradigm on scales of 3-6 Schwarzschild radii. The GRAVITY+ project will soon boost optical interferometry to the next level, opening up the extragalactic sky for milli-arcsecond resolution interferometric imaging, and providing ever higher contrast for the observation of exoplanets. This will be made possible with wide-field fringe-tracking, new state-of-the-art adaptive optics, laser guide stars, and performance improvements of GRAVITY and the VLT(I) infrastructure. We discuss some of the discovery space opening up with GRAVITY+, for example the detailed view on AGN at cosmic dawn, the detection and characterization of exoplanets and their atmospheres, the spin of the Galactic Center black hole, and microlenses tracing the Milky Ways dark components. Dr. Eisenhauer is hosted by Dr. Diederik Kruijssen (kruijssen@uni-heidelberg.de)
Dr. Frank Eisenhauer (MPI fuer Extraterrestrische Physik)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The GRAVITY instrument has enabled major steps forward in infrared interferometry, by phase-referenced imaging at milli-arcsecond resolution, with a sensitivity increase by factor thousands, 30-100 micro-arcsecond astrometry, and few micro-arcsecond differential spectro-astrometry. We give an overview of the technology behind GRAVITY and highlight the game-changing results from the first three years of operation. Our presentation takes us from nearby exoplanets all the way to distant quasars, with special focus on the Galactic Center, the first precision tests of Einstein?s theory of General Relativity around massive black holes, and tests of the massive black hole paradigm on scales of 3-6 Schwarzschild radii. The GRAVITY+ project will soon boost optical interferometry to the next level, opening up the extragalactic sky for milli-arcsecond resolution interferometric imaging, and providing ever higher contrast for the observation of exoplanets. This will be made possible with wide-field fringe-tracking, new state-of-the-art adaptive optics, laser guide stars, and performance improvements of GRAVITY and the VLT(I) infrastructure. We discuss some of the discovery space opening up with GRAVITY+, for example the detailed view on AGN at cosmic dawn, the detection and characterization of exoplanets and their atmospheres, the spin of the Galactic Center black hole, and microlenses tracing the Milky Ways dark components. Dr. Eisenhauer is hosted by Dr. Diederik Kruijssen (kruijssen@uni-heidelberg.de)
2021-06-15
16:00
16:00
Ultra-diffuse galaxies and their implications for galaxy formation and evolution
Prof. Pieter van Dokkum (Yale University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 In 2018 our group identified a large, diffuse galaxy that looked unlike any previously known object. It appeared to have a population of strange, very luminous globular clusters and - even more puzzling - appeared to lack any dark matter. Three years and a lot of controversy later the mystery has only deepened. I will present the latest findings from extremely deep Hubble images as well as new data from the Dragonfly Telephoto Array, the telescope that we are using to find low surface brightness emission. I will also touch on the implications for galaxy formation and the nature of dark matter. The talk will end with a preview of a major upgrade of the Dragonfly telescope. Prof. van Dokkum is hosted by Diederik Kruijssen (kruijssen@uni-heidelberg.de)
Prof. Pieter van Dokkum (Yale University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 In 2018 our group identified a large, diffuse galaxy that looked unlike any previously known object. It appeared to have a population of strange, very luminous globular clusters and - even more puzzling - appeared to lack any dark matter. Three years and a lot of controversy later the mystery has only deepened. I will present the latest findings from extremely deep Hubble images as well as new data from the Dragonfly Telephoto Array, the telescope that we are using to find low surface brightness emission. I will also touch on the implications for galaxy formation and the nature of dark matter. The talk will end with a preview of a major upgrade of the Dragonfly telescope. Prof. van Dokkum is hosted by Diederik Kruijssen (kruijssen@uni-heidelberg.de)
2021-06-08
16:00
16:00
New results from testing relativistic gravity with radio astronomy
Prof. Michael Kramer (MPI fuer Radioastronomie, Bonn)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 We experience a golden era in testing and exploring relativistic gravity. Whether it is results from gravitational wave detectors, satellite or lab experiments, radio astronomy plays an important complementary role. Here one can mention the cosmic microwave background, black hole imaging and, obviously, binary pulsars. This talk will provide a brief overview but will focus mostly on new results from study of strongly self-gravitating bodies with unrivalled precision. It compares the results to other methods and will give an outlook of what we can expect from new instruments such as MeerKAT, which already provides amazing results.
Prof. Michael Kramer (MPI fuer Radioastronomie, Bonn)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 We experience a golden era in testing and exploring relativistic gravity. Whether it is results from gravitational wave detectors, satellite or lab experiments, radio astronomy plays an important complementary role. Here one can mention the cosmic microwave background, black hole imaging and, obviously, binary pulsars. This talk will provide a brief overview but will focus mostly on new results from study of strongly self-gravitating bodies with unrivalled precision. It compares the results to other methods and will give an outlook of what we can expect from new instruments such as MeerKAT, which already provides amazing results.
2021-06-01
16:00
16:00
Black Holes in the Milky Way
Prof. Jessica Lu (UC Berkeley)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The population of stellar mass black holes in the Milky Way is almost entirely unexplored. Only a dozen black holes are confidently known in our Galaxy -- all in binaries. As a result, many basic properties of black holes remain uncertain at the order of magnitude level, including the total number of black holes in the Milky Way, the mass function, the binary fraction, and whether black holes receive kicks at birth. To constrain these properties, we need to find and study a larger population of black holes, both in isolation and in binary systems. High-precision astrometry is opening a new window onto black holes. I will present progress on our search for black holes using both gravitational lensing for isolated black holes and astrometric wobble for black holes in binaries. Professor Lu is jointly hosted by Joerg-Uwe Pott (jpott@mpia.de) and Nadine Neumayer (neumayer@mpia.de).
Prof. Jessica Lu (UC Berkeley)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The population of stellar mass black holes in the Milky Way is almost entirely unexplored. Only a dozen black holes are confidently known in our Galaxy -- all in binaries. As a result, many basic properties of black holes remain uncertain at the order of magnitude level, including the total number of black holes in the Milky Way, the mass function, the binary fraction, and whether black holes receive kicks at birth. To constrain these properties, we need to find and study a larger population of black holes, both in isolation and in binary systems. High-precision astrometry is opening a new window onto black holes. I will present progress on our search for black holes using both gravitational lensing for isolated black holes and astrometric wobble for black holes in binaries. Professor Lu is jointly hosted by Joerg-Uwe Pott (jpott@mpia.de) and Nadine Neumayer (neumayer@mpia.de).
2021-05-18
16:00
16:00
The riddle of binary black hole formation
Prof. Michela Mapelli (INAF Padova)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The latest results from the LIGO-Virgo-KAGRA collaboration draw a spectacular fresco of binary black hole mergers, ranging from a few to more than hundred solar masses. In this talk, I will discuss the main astrophysical formation channels of binary black holes, highlighting the open questions. On the one hand, models of stellar evolution and pair instability suggest the existence of a gap in the mass spectrum of black holes between ~60 and ~120 solar masses. The boundaries of this gap drastically depend on massive star evolution and on the efficiency of envelope removal during core collapse. On the other hand, extreme dynamical processes in dense star clusters can fill the mass gap, via multiple stellar collisions, dynamical exchanges and hierarchical mergers. These processes might build up intermediate-mass black holes with mass up to several thousand solar masses, especially in the most metal-poor and massive clusters. The evolution of such dynamical mergers across cosmic time will be one of the most exciting targets of next-generation ground-based detectors. Prof. Mapelli is being hosted by Prof. Ralf Klessen of the ITA institute (klessen@uni-heidelberg.de). Anyone interested in further discussions on specific topics should contact Prof. Klessen to arrange (virtual) follow-up meetings with Prof. Mapelli
Prof. Michela Mapelli (INAF Padova)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 The latest results from the LIGO-Virgo-KAGRA collaboration draw a spectacular fresco of binary black hole mergers, ranging from a few to more than hundred solar masses. In this talk, I will discuss the main astrophysical formation channels of binary black holes, highlighting the open questions. On the one hand, models of stellar evolution and pair instability suggest the existence of a gap in the mass spectrum of black holes between ~60 and ~120 solar masses. The boundaries of this gap drastically depend on massive star evolution and on the efficiency of envelope removal during core collapse. On the other hand, extreme dynamical processes in dense star clusters can fill the mass gap, via multiple stellar collisions, dynamical exchanges and hierarchical mergers. These processes might build up intermediate-mass black holes with mass up to several thousand solar masses, especially in the most metal-poor and massive clusters. The evolution of such dynamical mergers across cosmic time will be one of the most exciting targets of next-generation ground-based detectors. Prof. Mapelli is being hosted by Prof. Ralf Klessen of the ITA institute (klessen@uni-heidelberg.de). Anyone interested in further discussions on specific topics should contact Prof. Klessen to arrange (virtual) follow-up meetings with Prof. Mapelli
2021-05-11
16:00
16:00
Tracing AGN feedback signatures from small to large scales across cosmic time
Dr. Dominika Wylezalek (ZAH, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Abstract
https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 AGN feedback is now widely considered to be one of the main drivers in regulating the growth of massive galaxies. In my talk I will describe several efforts in our group to understand the power, reach and impact of AGN feedback processes. We find significant evidence for AGN feedback signatures even in low-luminosity AGN and we are now using molecular gas as a tracer to investigate if and how feedback may impact and quench galaxies at low redshift. At higher redshift, it appears that AGN-driven outflows can indeed suppress star formation in their hosts, consistent with the AGN having a `negative? impact on galaxy evolution. However, both star formation and quasar activity peak at z ~ 2-3 where AGN are expected to impact the build-up of stellar mass the most and I will present recent efforts in our group to characterise feedback processes in powerful AGN on CGM scales at and near Cosmic Noon. In particular, our team recently discovered a unique population of luminous high-z quasars (ERQs) with extreme outflow properties. At the same time, more and more exotic AGN populations with extreme signatures are being discovered at that redshift. These populations are ideal to obtain a census of the overall mass and energy budget of both outflow and infall/feeding from the CGM, an essential requirement to probe the detailed and full feedback loop. Finally, I will also introduce the JWST ERS Program "Q3D" which will study the impact of three carefully selected luminous quasars on their hosts. Our program will serve as a pathfinder for JWST science investigations in IFU mode.
Dr. Dominika Wylezalek (ZAH, University of Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 AGN feedback is now widely considered to be one of the main drivers in regulating the growth of massive galaxies. In my talk I will describe several efforts in our group to understand the power, reach and impact of AGN feedback processes. We find significant evidence for AGN feedback signatures even in low-luminosity AGN and we are now using molecular gas as a tracer to investigate if and how feedback may impact and quench galaxies at low redshift. At higher redshift, it appears that AGN-driven outflows can indeed suppress star formation in their hosts, consistent with the AGN having a `negative? impact on galaxy evolution. However, both star formation and quasar activity peak at z ~ 2-3 where AGN are expected to impact the build-up of stellar mass the most and I will present recent efforts in our group to characterise feedback processes in powerful AGN on CGM scales at and near Cosmic Noon. In particular, our team recently discovered a unique population of luminous high-z quasars (ERQs) with extreme outflow properties. At the same time, more and more exotic AGN populations with extreme signatures are being discovered at that redshift. These populations are ideal to obtain a census of the overall mass and energy budget of both outflow and infall/feeding from the CGM, an essential requirement to probe the detailed and full feedback loop. Finally, I will also introduce the JWST ERS Program "Q3D" which will study the impact of three carefully selected luminous quasars on their hosts. Our program will serve as a pathfinder for JWST science investigations in IFU mode.
2021-05-04
16:00
16:00
Thick as thieves - unveiling the most compact and obscured galaxy nuclei
Prof. Susanne Aalto (Chalmers University)
Heidelberg Joint Astronomical Colloquium
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https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 Cold gas plays a central role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei. Particularly powerful activity occurs when interactions of gas-rich galaxies funnel large amounts of gas and dust into nuclei of luminous and ultra luminous infrared galaxies (LIRGs/ULIRGs). These dusty objects are of key importance to galaxy mass assembly over cosmic time. Dust embedded galaxy evolution also occurs in less extreme galaxies, including nearby starbursts or enshrouded AGNs. Studying them is fundamental to our understanding of galaxy evolution. Some U/LIRGS have deeply embedded galaxy nuclei that harbour a particularly active evolutionary stage of AGNs and/or starbursts: the Compact Obscured Nuclei (CONs). The nuclear activity drives mechanical feedback in the form of molecular winds, jets and outflows. This feedback is key to processes that regulate multi-scale growth and our recent CONquest study show that as much as 20 40% of the U/LIRGs have CON nuclei. With mm/submm to FIR and IR telescopes, we can study the morphology, velocity structure, physical conditions and even chemistry of the obscured nuclei and their cold flows at unprecedented sensitivity and resolution. I will focus on recent ALMA, NOEMA and SMA studies of enshrouded nuclei, AGN and feedback. ALMA studies (resolution 0.02 arcsec(1 - 7 pc)), reveal launch regions of molecular outflows, inflows, and dusty nuclei of the nearby LIRGs NGC1068, NGC1377, Zw049 and IC860. The outflows are different from each other where NGC1068 shows gas carried out by a radio jet, while the more obscured galaxies NGC1377, Zw049 and IC860 have a radio-quiet collimated outflows, in different stages of evolution. I will also discuss how vibrationally excited molecular emission (e.g. HCN) can reach behind the curtain of dust to undertake new studies of heretofore hidden, rapid evolutionary phases of galaxy nuclei. Do CONs represent a new, unknown evolutionary phase of nuclear growth? Prof. Aalto is being hosted by Dr Richard Tuffs (Richard.Tuffs@mpi-hd.mpg.de). Anyone interested in further discussions on specific topics should contact Dr. Tuffs to arrange (virtual) follow-up meetings with Prof. Aalto.
Prof. Susanne Aalto (Chalmers University)
Heidelberg Joint Astronomical Colloquium
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https://zoom.us/j/97377192005?pwd=OUZPR1Z3ZGc5WDZPYW1SakEzV1pvQT09 Cold gas plays a central role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei. Particularly powerful activity occurs when interactions of gas-rich galaxies funnel large amounts of gas and dust into nuclei of luminous and ultra luminous infrared galaxies (LIRGs/ULIRGs). These dusty objects are of key importance to galaxy mass assembly over cosmic time. Dust embedded galaxy evolution also occurs in less extreme galaxies, including nearby starbursts or enshrouded AGNs. Studying them is fundamental to our understanding of galaxy evolution. Some U/LIRGS have deeply embedded galaxy nuclei that harbour a particularly active evolutionary stage of AGNs and/or starbursts: the Compact Obscured Nuclei (CONs). The nuclear activity drives mechanical feedback in the form of molecular winds, jets and outflows. This feedback is key to processes that regulate multi-scale growth and our recent CONquest study show that as much as 20 40% of the U/LIRGs have CON nuclei. With mm/submm to FIR and IR telescopes, we can study the morphology, velocity structure, physical conditions and even chemistry of the obscured nuclei and their cold flows at unprecedented sensitivity and resolution. I will focus on recent ALMA, NOEMA and SMA studies of enshrouded nuclei, AGN and feedback. ALMA studies (resolution 0.02 arcsec(1 - 7 pc)), reveal launch regions of molecular outflows, inflows, and dusty nuclei of the nearby LIRGs NGC1068, NGC1377, Zw049 and IC860. The outflows are different from each other where NGC1068 shows gas carried out by a radio jet, while the more obscured galaxies NGC1377, Zw049 and IC860 have a radio-quiet collimated outflows, in different stages of evolution. I will also discuss how vibrationally excited molecular emission (e.g. HCN) can reach behind the curtain of dust to undertake new studies of heretofore hidden, rapid evolutionary phases of galaxy nuclei. Do CONs represent a new, unknown evolutionary phase of nuclear growth? Prof. Aalto is being hosted by Dr Richard Tuffs (Richard.Tuffs@mpi-hd.mpg.de). Anyone interested in further discussions on specific topics should contact Dr. Tuffs to arrange (virtual) follow-up meetings with Prof. Aalto.
2021-04-27
16:00
16:00
Stellar explosions in multiple systems
Dr Ryosuke Hirai (Monash University)
Heidelberg Joint Astronomical Colloquium
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There are many forms of stellar explosions that are observed in the Universe, such as supernovae, kilonovae, X-ray bursts, stellar eruptions, etc. Many of these explosions originate from massive stars, which are predominantly members of binary or higher order multiple systems. Therefore the presence of companion stars may play a critical role in the mechanism of the explosion itself, or conversely, the explosion may affect the properties of the companion stars. In this talk, I will review our work on supernova explosions in binary systems, and stellar merger-driven eruptions in triple systems. I will show various examples where our numerical models reproduce the observed properties of some known explosions (e.g. supernova remnant Cassiopeia A, Great Eruption of Eta Carinae). I will also discuss how we can use the observations of stellar explosions to infer the evolution of the binary (or triple) system leading up to the explosion. Dr Hirai is being hosted by Dr Fabian Schneider of the HITS institute (fabian.schneider@h-its.org). Anyone interested in further discussions on specific topics should contact Dr. Schneider to arrange (virtual) follow-up meetings with Dr. Hirai.
Dr Ryosuke Hirai (Monash University)
Heidelberg Joint Astronomical Colloquium
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There are many forms of stellar explosions that are observed in the Universe, such as supernovae, kilonovae, X-ray bursts, stellar eruptions, etc. Many of these explosions originate from massive stars, which are predominantly members of binary or higher order multiple systems. Therefore the presence of companion stars may play a critical role in the mechanism of the explosion itself, or conversely, the explosion may affect the properties of the companion stars. In this talk, I will review our work on supernova explosions in binary systems, and stellar merger-driven eruptions in triple systems. I will show various examples where our numerical models reproduce the observed properties of some known explosions (e.g. supernova remnant Cassiopeia A, Great Eruption of Eta Carinae). I will also discuss how we can use the observations of stellar explosions to infer the evolution of the binary (or triple) system leading up to the explosion. Dr Hirai is being hosted by Dr Fabian Schneider of the HITS institute (fabian.schneider@h-its.org). Anyone interested in further discussions on specific topics should contact Dr. Schneider to arrange (virtual) follow-up meetings with Dr. Hirai.
2021-04-20
16:00
16:00
Space-time variation of the fundamental constants and dark matter
Prof. Victor Flambaum (University of New South Wales, Australia)
Heidelberg Joint Astronomical Colloquium
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The fundamental constants of nature such as electromagnetic fine structure constant alpha, strong interaction constant and fundamental masses may vary in expanding universe. Their variation in space may explain fine tuning of the fundamental constants needed for life to appear: we appeared in the area of the universe which is suitable for our existence. Indeed, data on quasar absorption spectra hint that alpha varies in space. This result needs a confirmation by other measurements. The effects of the variation have also been searched in Big Bang Nucleosynthesis and Cosmic Microwave Background data. An intensive search for the variation is carried out in numerous laboratories using atomic clocks. Interaction between dark matter and ordinary matter may produce variation of the fundamental constants. Low-mass boson dark matter particles produced after the Big Bang form a classical field. Effects produced by interaction of an ordinary matter with this field may be first power in the underlying interaction strength rather than the second power or higher (which appears in a traditional search for the dark matter). This may give enormous advantage since the dark matter interaction constant is extremely small. The primordial helium abundance data and atomic clock measurements allowed us to improve on existing constraints on the interactions of the scalar dark matter with photon, electron, quarks, Higgs, W and Z bosons by up to 15 orders of magnitude. In addition to these traditional methods to search for the variation of the fundamental constants we discuss variations in phase shifts produced in laser/maser interferometers (such as giant LIGO, Virgo and GEO600, and the table-top interferometers) and changes in pulsar rotational frequencies (which may have been observed already in pulsar glitches). Prof. Flambaum is being hosted by Dr Jose Crespo of the MPI Kernphysik (crespojr@mpi-hd.mpg.de). Anyone interested in further discussions on specific topics should contact Dr. Crespo to arrange (virtual) follow-up meetings with Prof. Flambaum.
Prof. Victor Flambaum (University of New South Wales, Australia)
Heidelberg Joint Astronomical Colloquium
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Abstract
The fundamental constants of nature such as electromagnetic fine structure constant alpha, strong interaction constant and fundamental masses may vary in expanding universe. Their variation in space may explain fine tuning of the fundamental constants needed for life to appear: we appeared in the area of the universe which is suitable for our existence. Indeed, data on quasar absorption spectra hint that alpha varies in space. This result needs a confirmation by other measurements. The effects of the variation have also been searched in Big Bang Nucleosynthesis and Cosmic Microwave Background data. An intensive search for the variation is carried out in numerous laboratories using atomic clocks. Interaction between dark matter and ordinary matter may produce variation of the fundamental constants. Low-mass boson dark matter particles produced after the Big Bang form a classical field. Effects produced by interaction of an ordinary matter with this field may be first power in the underlying interaction strength rather than the second power or higher (which appears in a traditional search for the dark matter). This may give enormous advantage since the dark matter interaction constant is extremely small. The primordial helium abundance data and atomic clock measurements allowed us to improve on existing constraints on the interactions of the scalar dark matter with photon, electron, quarks, Higgs, W and Z bosons by up to 15 orders of magnitude. In addition to these traditional methods to search for the variation of the fundamental constants we discuss variations in phase shifts produced in laser/maser interferometers (such as giant LIGO, Virgo and GEO600, and the table-top interferometers) and changes in pulsar rotational frequencies (which may have been observed already in pulsar glitches). Prof. Flambaum is being hosted by Dr Jose Crespo of the MPI Kernphysik (crespojr@mpi-hd.mpg.de). Anyone interested in further discussions on specific topics should contact Dr. Crespo to arrange (virtual) follow-up meetings with Prof. Flambaum.
2021-02-23
16:00
16:00
Physics under the gravitational rainbow
Claudia de Rham (Imperial College London)
Heidelberg Joint Astronomical Colloquium
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The recent direct detection of gravitational waves marks the beginning of a new era for physics and astronomy with an opportunity the probe gravity at its most fundamental level. I will discuss how the behaviour of gravity on large scales may differ from General Relativity and its implications for early and late-time cosmology as well as the potential signatures on the spectrum of gravitational waves observable at LIGO and LISA.
Claudia de Rham (Imperial College London)
Heidelberg Joint Astronomical Colloquium
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The recent direct detection of gravitational waves marks the beginning of a new era for physics and astronomy with an opportunity the probe gravity at its most fundamental level. I will discuss how the behaviour of gravity on large scales may differ from General Relativity and its implications for early and late-time cosmology as well as the potential signatures on the spectrum of gravitational waves observable at LIGO and LISA.
2021-02-16
16:00
16:00
Cosmic alchemy in the era of gravitational wave astronomy
Enrico Ramirez-Ruiz (UC Santa Cruz)
Heidelberg Joint Astronomical Colloquium
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The source of about half of the heaviest elements in the Universe has been a mystery for a long time. Although the general picture of element formation is well understood, many questions about the astrophysical details remain to be answered. Here I focus on recent advances in our understanding of the origin of the heaviest and rarest elements in the Universe.
Enrico Ramirez-Ruiz (UC Santa Cruz)
Heidelberg Joint Astronomical Colloquium
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The source of about half of the heaviest elements in the Universe has been a mystery for a long time. Although the general picture of element formation is well understood, many questions about the astrophysical details remain to be answered. Here I focus on recent advances in our understanding of the origin of the heaviest and rarest elements in the Universe.
2021-02-09
16:00
16:00
Simulating black hole dynamics and gravitational wave emission in galactic-scale simulations
Peter Johansson (University of Helsinki)
Heidelberg Joint Astronomical Colloquium
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Recently, large-scale cosmological simulations have been used to predict the gravitational wave background. These simulations typically rely on semi-analytic models to describe the small-scale black hole binary dynamics and gravitational wave emission, as these processes cannot be directly resolved in simulations employing gravitational softening. An alternative is to use a hybrid approach, such as the KETJU code, recently developed in our group. The KETJU code includes algorithmically regularised regions around every SMBH. This allows for simultaneously following global galactic-scale dynamical and astrophysical processes, while solving accurately the dynamics of SMBHs at sub-parsec scales. We show how the KETJU code can be used to study the formation of diffuse cores in very massive galaxies through the scouring by inspiraling supermassive black hole binaries. In addition, the KETJU code also includes post-Newtonian terms in the equations of motions of the SMBHs, which allows us to directly calculate the expected gravitational wave signal from the motion of the resolved SMBH binary in mergers of massive galaxies.
Peter Johansson (University of Helsinki)
Heidelberg Joint Astronomical Colloquium
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Recently, large-scale cosmological simulations have been used to predict the gravitational wave background. These simulations typically rely on semi-analytic models to describe the small-scale black hole binary dynamics and gravitational wave emission, as these processes cannot be directly resolved in simulations employing gravitational softening. An alternative is to use a hybrid approach, such as the KETJU code, recently developed in our group. The KETJU code includes algorithmically regularised regions around every SMBH. This allows for simultaneously following global galactic-scale dynamical and astrophysical processes, while solving accurately the dynamics of SMBHs at sub-parsec scales. We show how the KETJU code can be used to study the formation of diffuse cores in very massive galaxies through the scouring by inspiraling supermassive black hole binaries. In addition, the KETJU code also includes post-Newtonian terms in the equations of motions of the SMBHs, which allows us to directly calculate the expected gravitational wave signal from the motion of the resolved SMBH binary in mergers of massive galaxies.
2021-01-26
16:00
16:00
The fast rotating and low-turbulence discs of high-redshift galaxies
Filippo Fraternali (University of Groningen)
Heidelberg Joint Astronomical Colloquium
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After decades of being mostly confined to the local Universe, the study of gas dynamics has now become an essential tool to follow the evolution of galaxies across cosmic time. Gas rotation in galaxies allows us to trace the distribution of matter, quantify the mass of the dark matter halos and study galaxy scaling relations. In contrast, gas turbulence reveals the effects of stellar feedback and disc instabilities and provides clues about the formation of the stellar thin and thick discs. Moreover, rotation measurements allow us to estimate the build up of angular momentum in galaxies, which provides key tests for theoretical models of galaxy formation. In this talk, I will present results on high-z rotation curves and velocity dispersions, obtained through 3D reconstruction techniques of the emission-line datacubes. After discussing results at z~1, I will focus on ALMA observations of starburst galaxies at z~4 that reveal very fast rotation and surprisingly low velocity dispersions leading to V/sigma values >10. These results, on the one hand, provide dynamical evidence of the evolution of these massive systems into local early-type galaxies, but on the other hand, pose new critical challenges to our current understanding of galaxy formation at early times.
Filippo Fraternali (University of Groningen)
Heidelberg Joint Astronomical Colloquium
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After decades of being mostly confined to the local Universe, the study of gas dynamics has now become an essential tool to follow the evolution of galaxies across cosmic time. Gas rotation in galaxies allows us to trace the distribution of matter, quantify the mass of the dark matter halos and study galaxy scaling relations. In contrast, gas turbulence reveals the effects of stellar feedback and disc instabilities and provides clues about the formation of the stellar thin and thick discs. Moreover, rotation measurements allow us to estimate the build up of angular momentum in galaxies, which provides key tests for theoretical models of galaxy formation. In this talk, I will present results on high-z rotation curves and velocity dispersions, obtained through 3D reconstruction techniques of the emission-line datacubes. After discussing results at z~1, I will focus on ALMA observations of starburst galaxies at z~4 that reveal very fast rotation and surprisingly low velocity dispersions leading to V/sigma values >10. These results, on the one hand, provide dynamical evidence of the evolution of these massive systems into local early-type galaxies, but on the other hand, pose new critical challenges to our current understanding of galaxy formation at early times.
2021-01-19
16:00
16:00
Space asteroseismology: the Renaissance of stellar interiors
Conny Aerts (KU Leuven)
Heidelberg Joint Astronomical Colloquium
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The recent space age of uninterrupted high-precision photometry finally offered us a way to look deep inside stars. This deep probing is possible thanks to the detection of numerous stellar oscillations. The observed properties of such oscillations allow us to derive how stars age, how they rotate, and how they mix their gas throughout their life. In this Colloquium, we start with the basic ingredients of asteroseismology for the non-expert. We discuss the diversity of nonradial oscillations of stars, introducing pressure, gravity, magnetic, and tidal waves. We then emphasize some of the breakthroughs from space asteroseismology, focusing mostly on results from the 4-year Kepler light curves. Examples involve high-precision sizing, weighing, and ageing of stars throughout our Milky Way. We review the current status of the internal rotation of stars and offer a sneak-preview on internal mixing inside stars with a convective core as new observational input to calibrate stellar evolution theory. We end with a future outlook for this glorious research field of astrophysics, touching upon how to achieve probing of internal magnetism and tidal asteroseismology, thanks to the ongoing NASA TESS and future ESA PLATO space missions.
Conny Aerts (KU Leuven)
Heidelberg Joint Astronomical Colloquium
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The recent space age of uninterrupted high-precision photometry finally offered us a way to look deep inside stars. This deep probing is possible thanks to the detection of numerous stellar oscillations. The observed properties of such oscillations allow us to derive how stars age, how they rotate, and how they mix their gas throughout their life. In this Colloquium, we start with the basic ingredients of asteroseismology for the non-expert. We discuss the diversity of nonradial oscillations of stars, introducing pressure, gravity, magnetic, and tidal waves. We then emphasize some of the breakthroughs from space asteroseismology, focusing mostly on results from the 4-year Kepler light curves. Examples involve high-precision sizing, weighing, and ageing of stars throughout our Milky Way. We review the current status of the internal rotation of stars and offer a sneak-preview on internal mixing inside stars with a convective core as new observational input to calibrate stellar evolution theory. We end with a future outlook for this glorious research field of astrophysics, touching upon how to achieve probing of internal magnetism and tidal asteroseismology, thanks to the ongoing NASA TESS and future ESA PLATO space missions.
2021-01-12
16:00
16:00
Hot takes on cool worlds: exoplanet atmosphere characterization in the 2020s
Laura Kreidberg (MPIA)
Heidelberg Joint Astronomical Colloquium
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Exoplanets are now known to be common in the Galaxy, and the next step in studying these abundant worlds is to characterize their atmospheres. As new instrumentation and observing techniques develop, it is rapidly becoming possible to characterize smaller and cooler planets than ever before. In this talk, I will discuss the status quo in exoplanet atmosphere characterization, including recent measurements of sub-Neptune atmosphere composition and efforts to determine whether Earth-size planets have atmospheres at all. I will also overview the progress expected from next-generation observing facilities, including unprecedentedly precise measurements of the chemical composition and cloud properties of gaseous planets, and a first glimpse at the atmospheric and surface properties of rocky worlds.
Laura Kreidberg (MPIA)
Heidelberg Joint Astronomical Colloquium
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Exoplanets are now known to be common in the Galaxy, and the next step in studying these abundant worlds is to characterize their atmospheres. As new instrumentation and observing techniques develop, it is rapidly becoming possible to characterize smaller and cooler planets than ever before. In this talk, I will discuss the status quo in exoplanet atmosphere characterization, including recent measurements of sub-Neptune atmosphere composition and efforts to determine whether Earth-size planets have atmospheres at all. I will also overview the progress expected from next-generation observing facilities, including unprecedentedly precise measurements of the chemical composition and cloud properties of gaseous planets, and a first glimpse at the atmospheric and surface properties of rocky worlds.
2020-12-15
16:00
16:00
Red-giant stars inside out
Saskia Hekker (HITS/Heidelberg University)
Heidelberg Joint Astronomical Colloquium
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Did you know that we can probe the core of a red-giant star better than the core of the Sun? Actually, we do thanks to oscillations that are sensitive to the core that can be observed on the stellar surface. Over the past decade this has led to several groundbreaking discoveries. In this talk I will discuss these discoveries and explain how it is possible to look into the core of a red giant and not into the Sun.
Saskia Hekker (HITS/Heidelberg University)
Heidelberg Joint Astronomical Colloquium
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Did you know that we can probe the core of a red-giant star better than the core of the Sun? Actually, we do thanks to oscillations that are sensitive to the core that can be observed on the stellar surface. Over the past decade this has led to several groundbreaking discoveries. In this talk I will discuss these discoveries and explain how it is possible to look into the core of a red giant and not into the Sun.
2020-12-08
16:00
16:00
The genesis of the first elements
Ryan Cooke (Durham University)
Heidelberg Joint Astronomical Colloquium
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Ryan Cooke (Durham University)
Heidelberg Joint Astronomical Colloquium
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2020-12-08
16:00
16:00
The puzzle of multiple populations in globular clusters
Nate Bastian (LJMU)
Heidelberg Joint Astronomical Colloquium
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Globular clusters (GCs) exhibit star-to-star variations in specific elements (e.g., He, C, N, O, Na, Al) that bear the hallmark of high-temperature H-burning. These abundance variations can be observed spectroscopically and also photometrically, with the appropriate choice of filters, due to the changing of spectral features within the band pass. This phenomenon is observed in nearly all of the ancient GCs, and has recently been found in many younger clusters as well. Many scenarios have been suggested to explain this phenomenon, with most invoking multiple epochs of star formation within the cluster; however, all have failed to reproduce various key observations. I will review the state of current observations and outline the successes and failures of some of the main proposed models. The traditional idea of using the stellar ejecta from a first generation of stars to form a second generation of stars, while conceptually straightforward, has failed to reproduce an increasing number of observational constraints. I conclude that the puzzle of multiple populations remains unsolved, hence alternative theories are needed, and will present new HST and VLT/MUSE results that suggest that we may be finally closing in on origin of this enigmatic phenomenon.
Nate Bastian (LJMU)
Heidelberg Joint Astronomical Colloquium
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Globular clusters (GCs) exhibit star-to-star variations in specific elements (e.g., He, C, N, O, Na, Al) that bear the hallmark of high-temperature H-burning. These abundance variations can be observed spectroscopically and also photometrically, with the appropriate choice of filters, due to the changing of spectral features within the band pass. This phenomenon is observed in nearly all of the ancient GCs, and has recently been found in many younger clusters as well. Many scenarios have been suggested to explain this phenomenon, with most invoking multiple epochs of star formation within the cluster; however, all have failed to reproduce various key observations. I will review the state of current observations and outline the successes and failures of some of the main proposed models. The traditional idea of using the stellar ejecta from a first generation of stars to form a second generation of stars, while conceptually straightforward, has failed to reproduce an increasing number of observational constraints. I conclude that the puzzle of multiple populations remains unsolved, hence alternative theories are needed, and will present new HST and VLT/MUSE results that suggest that we may be finally closing in on origin of this enigmatic phenomenon.
2020-12-01
16:00
16:00
Frontiers of high-energy computational astrophysics: bridging gaps between large and small scales
Andrea Mignone (University of Turin)
Heidelberg Joint Astronomical Colloquium
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High-energy non-thermal astrophysical environments - such as Active Galactic Nuclei, Pulsar Wind Nebulae and Gamma Ray burst - involve magnetized relativistic flows, whose energy flux can be partly converted, at dissipation sites, into random relativistic motion of particles that lose their energy through a variety of non-thermal processes and give rise to the observed radiation. Understanding of these extreme environments requires a detailed description of the highly nonlinear interactions between plasmas, non-thermal relativistic particles and radiation taking place on a wide range of spatial and temporal scales. This has forced practitioners in the field to take a sectorial approach. On the one hand, models at the large scale can be obtained through relativistic magnetohydrodynamical (RMHD) numerical simulations using a fluid model, albeit neglecting the relativistic particle component. On the other, Particle In Cell (PIC) codes allow a deeper comprehension of kinetic phenomena taking place at much smaller scales. As a consequence, the resulting picture is incomplete and fragmentary. In this talk, I will discuss some of the present and future computational perspectives which intend to bridge this gap. This task requires the coupling between large scale dynamics with a detailed treatment of the microphysics at dissipation sites, an extremely challenging task that only now is becoming feasible thanks to the advancements of high performance computing.
Andrea Mignone (University of Turin)
Heidelberg Joint Astronomical Colloquium
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High-energy non-thermal astrophysical environments - such as Active Galactic Nuclei, Pulsar Wind Nebulae and Gamma Ray burst - involve magnetized relativistic flows, whose energy flux can be partly converted, at dissipation sites, into random relativistic motion of particles that lose their energy through a variety of non-thermal processes and give rise to the observed radiation. Understanding of these extreme environments requires a detailed description of the highly nonlinear interactions between plasmas, non-thermal relativistic particles and radiation taking place on a wide range of spatial and temporal scales. This has forced practitioners in the field to take a sectorial approach. On the one hand, models at the large scale can be obtained through relativistic magnetohydrodynamical (RMHD) numerical simulations using a fluid model, albeit neglecting the relativistic particle component. On the other, Particle In Cell (PIC) codes allow a deeper comprehension of kinetic phenomena taking place at much smaller scales. As a consequence, the resulting picture is incomplete and fragmentary. In this talk, I will discuss some of the present and future computational perspectives which intend to bridge this gap. This task requires the coupling between large scale dynamics with a detailed treatment of the microphysics at dissipation sites, an extremely challenging task that only now is becoming feasible thanks to the advancements of high performance computing.
2020-11-17
16:00
16:00
Our astrochemical origins
Paola Caselli (MPE)
Heidelberg Joint Astronomical Colloquium
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Our Solar System was born from a dark and cold cloud made out of molecular gas and small dust particles. Thanks to powerful telescopes, we can now study in detail these clouds, their chemical ingredients and their evolution. We can then reconstruct our origins. Interstellar molecules are unique tracers of the dynamical and chemical evolution of star and planet forming regions. Thus, astrochemistry is crucial to test theories and shed light on our origins. In this talk I shall review the chemical and physical structure of interstellar clouds, where stars and planets are formed, as well as theoretical work on protoplanetary disk formation and early evolution. Links to our Solar System will be made.
Paola Caselli (MPE)
Heidelberg Joint Astronomical Colloquium
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Our Solar System was born from a dark and cold cloud made out of molecular gas and small dust particles. Thanks to powerful telescopes, we can now study in detail these clouds, their chemical ingredients and their evolution. We can then reconstruct our origins. Interstellar molecules are unique tracers of the dynamical and chemical evolution of star and planet forming regions. Thus, astrochemistry is crucial to test theories and shed light on our origins. In this talk I shall review the chemical and physical structure of interstellar clouds, where stars and planets are formed, as well as theoretical work on protoplanetary disk formation and early evolution. Links to our Solar System will be made.
2020-11-10
16:00
16:00
Origin and evolution of cosmic magnetic fields
Jennifer Schober (EPFL)
Heidelberg Joint Astronomical Colloquium
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Magnetic fields are observed on virtually all scales of the modern Universe, from planets and stars to galaxies and galaxy clusters. Observations of blazars suggest that even cosmic voids are permeated by magnetic fields. Being correlated on Mpc-scales, these intergalactic magnetic fields were most likely generated very shortly after the Big Bang and therefore open up a unique window into the physics of the very early Universe. In my colloquium, I will review theoretical models of magnetogenesis and confront these with observational constraints. I will address the possible origin of magnetic fields in the very early Universe, during inflation and the cosmological phase transitions, as well as their pre-recombination evolution in decaying magnetohydrodynamical (MHD) turbulence. Finally, I will present results from high-resolution numerical simulations that show an efficient amplification of magnetic energy due to the so-called chiral anomaly, a standard model effect that necessarily leads to an extension of MHD at high temperatures such as in the early Universe.
Jennifer Schober (EPFL)
Heidelberg Joint Astronomical Colloquium
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Magnetic fields are observed on virtually all scales of the modern Universe, from planets and stars to galaxies and galaxy clusters. Observations of blazars suggest that even cosmic voids are permeated by magnetic fields. Being correlated on Mpc-scales, these intergalactic magnetic fields were most likely generated very shortly after the Big Bang and therefore open up a unique window into the physics of the very early Universe. In my colloquium, I will review theoretical models of magnetogenesis and confront these with observational constraints. I will address the possible origin of magnetic fields in the very early Universe, during inflation and the cosmological phase transitions, as well as their pre-recombination evolution in decaying magnetohydrodynamical (MHD) turbulence. Finally, I will present results from high-resolution numerical simulations that show an efficient amplification of magnetic energy due to the so-called chiral anomaly, a standard model effect that necessarily leads to an extension of MHD at high temperatures such as in the early Universe.
2020-02-04
16:30
16:30
Burning Down the House: Star Formation and Feedback in Giant Molecular Clouds
Eve Ostriker (Princeton University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Giant molecular clouds (GMCs) are the home of the most extreme conditions and the most dramatic events found in the interstellar medium (ISM). As hosts of the densest, coldest portion of the ISM’s gas, gravitational collapse is inevitable, and leads to the formation of star clusters. These young star clusters, in turn, host massive and luminous stars that profoundly alter — and ultimately destroy — their birth clouds, by a combination of photoevaporation, radiation forces on dust, and strong shocks from winds and supernovae. Because GMCs are porous, the energy injected by massive stars also escapes to power the surrounding ISM. Given the complex array of processes involved, numerical simulations are essential to developing quantitative models of the lives and deaths of star-forming GMCs. In this talk, I will describe results from recent radiation (magneto-) hydrodynamic simulations that have helped us to understand how star-forming GMCs self-regulate, while simultaneously regulating the thermal, ionization, and turbulent states of the distant diffuse ISM.
Eve Ostriker (Princeton University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Giant molecular clouds (GMCs) are the home of the most extreme conditions and the most dramatic events found in the interstellar medium (ISM). As hosts of the densest, coldest portion of the ISM’s gas, gravitational collapse is inevitable, and leads to the formation of star clusters. These young star clusters, in turn, host massive and luminous stars that profoundly alter — and ultimately destroy — their birth clouds, by a combination of photoevaporation, radiation forces on dust, and strong shocks from winds and supernovae. Because GMCs are porous, the energy injected by massive stars also escapes to power the surrounding ISM. Given the complex array of processes involved, numerical simulations are essential to developing quantitative models of the lives and deaths of star-forming GMCs. In this talk, I will describe results from recent radiation (magneto-) hydrodynamic simulations that have helped us to understand how star-forming GMCs self-regulate, while simultaneously regulating the thermal, ionization, and turbulent states of the distant diffuse ISM.
2020-01-28
16:30
16:30
A definitive test of the cold dark matter model: no ifs or buts
Carlos Frenk (Durham University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The ``Lambda cold dark matter'' (LCDM) cosmological model is one of the great achievements in Physics of the past thirty years. Theoretical predictions formulated in the 1980s turned out to agree remarkably well with measurements, performed decades later, of the galaxy distribution and the temperature structure of the cosmic microwave background radiation. Yet, these successes do not inform us directly about the nature of the dark matter. Indeed, there are competing (and controversial) claims that the dark matter may have already been discovered, either through the annihilation of cold, or the decay of warm, dark matter particles. In astrophysics the identity of the dark matter manifests itself clearly on subgalactic scales, including the dwarf satellite galaxies of the Milky Way and especially less massive dark matter halos, too small to have made a galaxy. I will discuss predictions from cosmological simulations assuming cold and warm (in the form of sterile neutrinos) dark matter and show how forthcoming astronomical observations can conclusively distinguish between the two.
Carlos Frenk (Durham University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The ``Lambda cold dark matter'' (LCDM) cosmological model is one of the great achievements in Physics of the past thirty years. Theoretical predictions formulated in the 1980s turned out to agree remarkably well with measurements, performed decades later, of the galaxy distribution and the temperature structure of the cosmic microwave background radiation. Yet, these successes do not inform us directly about the nature of the dark matter. Indeed, there are competing (and controversial) claims that the dark matter may have already been discovered, either through the annihilation of cold, or the decay of warm, dark matter particles. In astrophysics the identity of the dark matter manifests itself clearly on subgalactic scales, including the dwarf satellite galaxies of the Milky Way and especially less massive dark matter halos, too small to have made a galaxy. I will discuss predictions from cosmological simulations assuming cold and warm (in the form of sterile neutrinos) dark matter and show how forthcoming astronomical observations can conclusively distinguish between the two.
2020-01-21
16:30
16:30
The 3D view on stellar astrophysics
Friedrich Roepke (HITS/Heidelberg University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The theoretical description of stars is plagued with severe scale problems: the many physical processes at play act on vastly different spatial and temporal scales. The classical approach to deal with this problem has been to formulate the underlying equations assuming spherical symmetry and hydrostatic equilibrium thus allowing for (numerical) solutions that explain the main phases of stellar evolution and reproduce many observables. This success, however, came at a price: casting inherently multidimensional physical processes in a one-dimensional framework required strong parametrization and sometimes even tinkering with the underlying physics. This diminishes the predictive power of stellar models and improvements are required to interpret and guide current and future observations. The next generation of stellar models clearly has to be build on multidimensional simulations. Are current (super-)computational resources sufficient to meet this challenge? What numerical techniques are required to enable simulations of challenging multi-physics, multi-scale stellar models? I will discuss three examples where a one-dimensional treatment clearly fails: convection and hydrodynamical instabilities ins stellar interiors, stellar explosions, and binary stellar evolution. These cases illustrate how the rapid evolution of computational astrophysics enables progress in stellar modeling.
Friedrich Roepke (HITS/Heidelberg University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The theoretical description of stars is plagued with severe scale problems: the many physical processes at play act on vastly different spatial and temporal scales. The classical approach to deal with this problem has been to formulate the underlying equations assuming spherical symmetry and hydrostatic equilibrium thus allowing for (numerical) solutions that explain the main phases of stellar evolution and reproduce many observables. This success, however, came at a price: casting inherently multidimensional physical processes in a one-dimensional framework required strong parametrization and sometimes even tinkering with the underlying physics. This diminishes the predictive power of stellar models and improvements are required to interpret and guide current and future observations. The next generation of stellar models clearly has to be build on multidimensional simulations. Are current (super-)computational resources sufficient to meet this challenge? What numerical techniques are required to enable simulations of challenging multi-physics, multi-scale stellar models? I will discuss three examples where a one-dimensional treatment clearly fails: convection and hydrodynamical instabilities ins stellar interiors, stellar explosions, and binary stellar evolution. These cases illustrate how the rapid evolution of computational astrophysics enables progress in stellar modeling.
2020-01-14
16:30
16:30
The Origin of Turbulence in the Interstellar Medium
Mark Krumholz (Australian National University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In this talk, I review attempts to build a self-consistent model for the origin of turbulence of the interstellar medium (ISM) in star-forming galactic discs. Ideally such a model would incorporate all potential sources of turbulence: stellar feedback, gravitational and other instabilities, and driving by stellar gravity, and would be able to explain observed correlations between ISM turbulence and other properties of galaxies, such as their star formation rates. I summarise the various ways that theorists have attempted to fit together physical ingredients to reach this goal, the differing physical pictures behind these models, and the strengths and weaknesses of each when it comes to reproducing the observations. I then show that it is possible to combine the best elements of these models into a single, unified picture that explains the relative roles of the various sources of turbulence, and successfully reproduces most of the major observations. I suggest future observations and numerical experiments that can be used to test this unified model.
Mark Krumholz (Australian National University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In this talk, I review attempts to build a self-consistent model for the origin of turbulence of the interstellar medium (ISM) in star-forming galactic discs. Ideally such a model would incorporate all potential sources of turbulence: stellar feedback, gravitational and other instabilities, and driving by stellar gravity, and would be able to explain observed correlations between ISM turbulence and other properties of galaxies, such as their star formation rates. I summarise the various ways that theorists have attempted to fit together physical ingredients to reach this goal, the differing physical pictures behind these models, and the strengths and weaknesses of each when it comes to reproducing the observations. I then show that it is possible to combine the best elements of these models into a single, unified picture that explains the relative roles of the various sources of turbulence, and successfully reproduces most of the major observations. I suggest future observations and numerical experiments that can be used to test this unified model.
2020-01-07
16:30
16:30
Successes and challenges in modelling massive stars in one and multiple dimensions
Raphael Hirschi (Keele University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Stars are complex objects involving multi-dimensional processes like convection, rotation and magnetic fields. Ideally, we would like to model stars with three-dimensional (3D) magneto-hydrodynamic (MHD) simulations but it is unfortunately not feasible to simulate their entire evolution in 3D. Stars, including massive stars, have thus mostly been modelled in 1D assuming spherical symmetry. Theoretical prescriptions are used to determine the 1D (time- and spherically-averaged) effects of the multi-D processes listed above into the 1D models. This has been quite successful over the past 50 years or so. The continuously improving observational constraints, however, have highlighted key deficiencies of the present 1D models. In particular asteroseismic constraints cannot be reproduced with stellar models including standard prescriptions of convection and rotation. With the increase in computing power with time, we now have the power to complement observational constraints with constraints from 3D (M)HD simulations of stellar interiors. In this talk, I will first give a brief introduction to 1D stellar evolution modelling and review some of its successes. I will then introduce a framework to develop synergy between 3D and 1D simulations of convection, the so-called RA-ILES framework. I will present recent results obtained by applying this framework to convective boundary mixing, which is one of the most important uncertainties in the evolution of stars of all masses. I will also discuss the topic of angular momentum transport and the related chemical mixing in stars. In this case, it is harder to use 3D simulations but we can use nucleosynthesis to complement other observational constraints. I will end the talk with a summary and outlook.
Raphael Hirschi (Keele University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
Stars are complex objects involving multi-dimensional processes like convection, rotation and magnetic fields. Ideally, we would like to model stars with three-dimensional (3D) magneto-hydrodynamic (MHD) simulations but it is unfortunately not feasible to simulate their entire evolution in 3D. Stars, including massive stars, have thus mostly been modelled in 1D assuming spherical symmetry. Theoretical prescriptions are used to determine the 1D (time- and spherically-averaged) effects of the multi-D processes listed above into the 1D models. This has been quite successful over the past 50 years or so. The continuously improving observational constraints, however, have highlighted key deficiencies of the present 1D models. In particular asteroseismic constraints cannot be reproduced with stellar models including standard prescriptions of convection and rotation. With the increase in computing power with time, we now have the power to complement observational constraints with constraints from 3D (M)HD simulations of stellar interiors. In this talk, I will first give a brief introduction to 1D stellar evolution modelling and review some of its successes. I will then introduce a framework to develop synergy between 3D and 1D simulations of convection, the so-called RA-ILES framework. I will present recent results obtained by applying this framework to convective boundary mixing, which is one of the most important uncertainties in the evolution of stars of all masses. I will also discuss the topic of angular momentum transport and the related chemical mixing in stars. In this case, it is harder to use 3D simulations but we can use nucleosynthesis to complement other observational constraints. I will end the talk with a summary and outlook.
2019-12-17
16:30
16:30
Cupules, Whales and Croziers - Pole-finding and Centralisms in Neolithic Brittany, ca. 5000 - 2500 BC
Stefan Maeder (Freiburger Institut fuer Palaeowissenschaften)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Drawing from the archaeological, astronomical, and symbolical record, recurring patterns in cupule arrangements, as well as two literally central motifs from Neolithic funerary contexts in the Morbihan region of Brittany, France, are introduced and interpreted. In this region anthropogenic cupules/cupmarks (round depressions in rock surfaces, often between 4 and 10 cm diametre) occur mainly on megalithic monuments, rarely on rock outcrops. The “sperm-whale” (fr. “cachalot”) and the “crozier” (fr. “crosse”) occur on menhirs/steles (“standing-stones”) hitherto dated to around the middle of the 5th millennium BC, as well as on central-capstones and orthostats in slightly later passage-graves commonly dated to ca. 4200 - 3900 BC. Here, the often combined and seemingly disparate representations of both motifs are associated for the first time with the phenomenon of precession of the earth´s polar axis. “With respect to spatial orientation, navigation, chronometry, as well as underlying worldviews and aspects of funerary culture (i.e. cosmologies), the apparent and changing centre of the cosmos, the Northern Celestial Pole (NCP), and conspicuous circumpolar asterisms played a pivotal role in Neolithic Europe also.” Since 2009 this working hypothesis proved valid in a variety of instances between Japan and Ireland. In 2017, two asterisms of a “sperm-whale” and “crozier“, closely matching the outline of four 5th millennium BC engravings from Locmariaquer, were identified as concrete and still easily verifiable pole-finders in 4600 BC (+/- 200 years). These not only provide a detailed explanation for accepted regularities concerning megalithic funerary and ritual monuments, but further elaborate most recently published results in support of a “maritime diffusion model for megaliths in Europe”. The presentation is intended as a probe into the largely neglected perspectives of a systematic cooperation between the next generation of astronomers and archaeologists, concerning the pre-history of astronomical observations and their application for navigational and ritual purposes.
Stefan Maeder (Freiburger Institut fuer Palaeowissenschaften)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
Drawing from the archaeological, astronomical, and symbolical record, recurring patterns in cupule arrangements, as well as two literally central motifs from Neolithic funerary contexts in the Morbihan region of Brittany, France, are introduced and interpreted. In this region anthropogenic cupules/cupmarks (round depressions in rock surfaces, often between 4 and 10 cm diametre) occur mainly on megalithic monuments, rarely on rock outcrops. The “sperm-whale” (fr. “cachalot”) and the “crozier” (fr. “crosse”) occur on menhirs/steles (“standing-stones”) hitherto dated to around the middle of the 5th millennium BC, as well as on central-capstones and orthostats in slightly later passage-graves commonly dated to ca. 4200 - 3900 BC. Here, the often combined and seemingly disparate representations of both motifs are associated for the first time with the phenomenon of precession of the earth´s polar axis. “With respect to spatial orientation, navigation, chronometry, as well as underlying worldviews and aspects of funerary culture (i.e. cosmologies), the apparent and changing centre of the cosmos, the Northern Celestial Pole (NCP), and conspicuous circumpolar asterisms played a pivotal role in Neolithic Europe also.” Since 2009 this working hypothesis proved valid in a variety of instances between Japan and Ireland. In 2017, two asterisms of a “sperm-whale” and “crozier“, closely matching the outline of four 5th millennium BC engravings from Locmariaquer, were identified as concrete and still easily verifiable pole-finders in 4600 BC (+/- 200 years). These not only provide a detailed explanation for accepted regularities concerning megalithic funerary and ritual monuments, but further elaborate most recently published results in support of a “maritime diffusion model for megaliths in Europe”. The presentation is intended as a probe into the largely neglected perspectives of a systematic cooperation between the next generation of astronomers and archaeologists, concerning the pre-history of astronomical observations and their application for navigational and ritual purposes.
2019-12-10
16:30
16:30
The subsurface ocean of Enceladus: A habitable place in our solar system
Frank Postberg (Freie Universitaet Berlin)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Saturn’s icy moon Enceladus harbours a global ocean, which lies under an ice crust of just a few kilometres thickness and above a rocky core. Through warm cracks in the crust a cryo-volcanic plume ejects ice grains and vapour into space providing access to materials originating from the ocean. The ocean is 30–55 km deep and provides an environment of mild salinity and alkaline pH. Hydrothermal activity is suspected to be occurring at the bottom of the ocean and also deep inside the water-percolated porous core. The energy is delivered by tidal dissipation. Two mass spectrometers aboard the Cassini spacecraft, the Cosmic Dust Analyzer (CDA) and the Ion and Neutral Gas Spectrometer (INMS) frequently carried out compositional in situ measurements of plume material emerging from the subsurface of Enceladus. Our latest results now show that, in addition to volatile organic compounds, some emitted ice grains contain concentrated macromolecular organic material with molecular masses clearly above 200u. Moreover, the mass spectra of the two instruments provide key constraints on the macromolecular structure. We suggest that the detected organic compounds and other materials found in the plume originate from Enceladus' hydrothermally active rocky core. Thermal ocean convection together with bubbles of volatile gases, transports these materials from the moon’s hydrothermal core up to the ocean surface. There, a spray of salty water together with droplets of solid organic nucleation cores - generated by bubble bursting and subsequently coated with ice from vapor freezing - are ejected into space.
Frank Postberg (Freie Universitaet Berlin)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Saturn’s icy moon Enceladus harbours a global ocean, which lies under an ice crust of just a few kilometres thickness and above a rocky core. Through warm cracks in the crust a cryo-volcanic plume ejects ice grains and vapour into space providing access to materials originating from the ocean. The ocean is 30–55 km deep and provides an environment of mild salinity and alkaline pH. Hydrothermal activity is suspected to be occurring at the bottom of the ocean and also deep inside the water-percolated porous core. The energy is delivered by tidal dissipation. Two mass spectrometers aboard the Cassini spacecraft, the Cosmic Dust Analyzer (CDA) and the Ion and Neutral Gas Spectrometer (INMS) frequently carried out compositional in situ measurements of plume material emerging from the subsurface of Enceladus. Our latest results now show that, in addition to volatile organic compounds, some emitted ice grains contain concentrated macromolecular organic material with molecular masses clearly above 200u. Moreover, the mass spectra of the two instruments provide key constraints on the macromolecular structure. We suggest that the detected organic compounds and other materials found in the plume originate from Enceladus' hydrothermally active rocky core. Thermal ocean convection together with bubbles of volatile gases, transports these materials from the moon’s hydrothermal core up to the ocean surface. There, a spray of salty water together with droplets of solid organic nucleation cores - generated by bubble bursting and subsequently coated with ice from vapor freezing - are ejected into space.
2019-12-03
16:30
16:30
Dense gas and star formation in nearby starburst galaxies with ALMA
Christine Wilson (McMaster University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
With its high sensitivity, excellent angular resolution, and wide spectral coverage, ALMA is revolutionizing our view of galaxies in the nearby universe. ALMA is particularly important for studying the dense molecular gas that is the fuel for star formation. Radio continuum emission from ALMA is also an important measure of the star formation rate, particularly in galaxies with high visual extinction such as starburst galaxies and luminous infrared galaxies. Finally, the ALMA archive contains an ever-growing collection of data that can be mined and combined to produce large samples of targets that can match or exceed the amount of observing invested in a single ALMA large program. I will describe our work on the link between dense gas and star formation for a sample of 9 nearby galaxies from the ALMA archive, which includes measuring the resolved Kennicutt-Schmidt star formation law at extreme star formation rate surface densities and identifying a new molecular line that appears to be an excellent tracer of the densest star forming gas.
Christine Wilson (McMaster University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
With its high sensitivity, excellent angular resolution, and wide spectral coverage, ALMA is revolutionizing our view of galaxies in the nearby universe. ALMA is particularly important for studying the dense molecular gas that is the fuel for star formation. Radio continuum emission from ALMA is also an important measure of the star formation rate, particularly in galaxies with high visual extinction such as starburst galaxies and luminous infrared galaxies. Finally, the ALMA archive contains an ever-growing collection of data that can be mined and combined to produce large samples of targets that can match or exceed the amount of observing invested in a single ALMA large program. I will describe our work on the link between dense gas and star formation for a sample of 9 nearby galaxies from the ALMA archive, which includes measuring the resolved Kennicutt-Schmidt star formation law at extreme star formation rate surface densities and identifying a new molecular line that appears to be an excellent tracer of the densest star forming gas.
2019-11-26
16:30
16:30
The Galactic Halo Renaissance
Alis Deason (Durham University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We are currently witnessing a golden age in Galactic halo science. Largely thanks to the Gaia mission, we now have phase-space plus chemical information for significant numbers of halo stars, globular clusters and satellite dwarf galaxies in the Milky Way. These halo populations can be used to uncover the assembly history of the Galaxy, probe the nature of dark matter, and scrutinise cosmological models. In this talk I will describe recent efforts to address these fundamental questions using a combination of new observational data and state-of-the-art cosmological simulations. In particular, I will discuss the total mass and mass profile of the Milky Way, the last major accretion event that shaped the Galaxy's history, and the (surviving and destroyed) dwarf satellite luminosity function.
Alis Deason (Durham University)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We are currently witnessing a golden age in Galactic halo science. Largely thanks to the Gaia mission, we now have phase-space plus chemical information for significant numbers of halo stars, globular clusters and satellite dwarf galaxies in the Milky Way. These halo populations can be used to uncover the assembly history of the Galaxy, probe the nature of dark matter, and scrutinise cosmological models. In this talk I will describe recent efforts to address these fundamental questions using a combination of new observational data and state-of-the-art cosmological simulations. In particular, I will discuss the total mass and mass profile of the Milky Way, the last major accretion event that shaped the Galaxy's history, and the (surviving and destroyed) dwarf satellite luminosity function.
2019-11-19
16:30
16:30
Radiation-dominated Black Hole Accretion Flows
Jim Stone (Institute for Advanced Study)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
At high accretion rates, the outward force of radiation pressure generated by energy released by infalling matter can exceed the inward pull of gravity. Such super-Eddington accretion flows occur in many systems, such as the inner regions of quasars and luminous AGN, ultra-luminous X-ray sources (ULXs), and tidal disruption events. Understanding such flows is important not only for interpreting the spectra and variability of these sources, but also to predict the rate of growth of black holes in the early universe, and to quantify energy and momentum feedback into the medium surrounding the black hole, a process likely to be important in galaxy formation. New results from a study of the magnetohydrodynamics of luminous accretion flows, in which radiation pressure dominates, will be presented. Our results reveal new physical effects, such as turbulent transport of radiation energy, that require extension of standard thin-disk models. We discuss the implications of our results for the astrophysics of accreting black holes.
Jim Stone (Institute for Advanced Study)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
At high accretion rates, the outward force of radiation pressure generated by energy released by infalling matter can exceed the inward pull of gravity. Such super-Eddington accretion flows occur in many systems, such as the inner regions of quasars and luminous AGN, ultra-luminous X-ray sources (ULXs), and tidal disruption events. Understanding such flows is important not only for interpreting the spectra and variability of these sources, but also to predict the rate of growth of black holes in the early universe, and to quantify energy and momentum feedback into the medium surrounding the black hole, a process likely to be important in galaxy formation. New results from a study of the magnetohydrodynamics of luminous accretion flows, in which radiation pressure dominates, will be presented. Our results reveal new physical effects, such as turbulent transport of radiation energy, that require extension of standard thin-disk models. We discuss the implications of our results for the astrophysics of accreting black holes.
2019-11-12
16:30
16:30
The Cradle of Planets: From Cosmic Dust to Planetesimals
Paola Pinilla (MPIA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In this new era of powerful telescopes such as ALMA, we are now able to study the birth of planets in disks around young stars, in more detail than ever before. New observations are revealing fascinating structures in protoplanetary disks that are transforming our understanding of the formation and evolution of planetary systems. In this colloquium, I will explain theoretical models of dust evolution in protoplanetary disks and I will compare these theoretical predictions with current multi-wavelength disk observations. This link is providing significant insights about how different physical conditions play a crucial role in the formation of the first planetesimals, and is extending our understanding of how initial conditions of protoplanetary disks are reflected in the large diversity of extrasolar systems observed up today.
Paola Pinilla (MPIA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In this new era of powerful telescopes such as ALMA, we are now able to study the birth of planets in disks around young stars, in more detail than ever before. New observations are revealing fascinating structures in protoplanetary disks that are transforming our understanding of the formation and evolution of planetary systems. In this colloquium, I will explain theoretical models of dust evolution in protoplanetary disks and I will compare these theoretical predictions with current multi-wavelength disk observations. This link is providing significant insights about how different physical conditions play a crucial role in the formation of the first planetesimals, and is extending our understanding of how initial conditions of protoplanetary disks are reflected in the large diversity of extrasolar systems observed up today.
2019-11-05
16:30
16:30
The rise of the Milky Way
Joao Alves (University of Vienna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Most of what we know about star and planet formation has been secured from spatial 2D observations of the local Galactic neighborhood, collected over the last 70 years. During this time we have established a series of ground truths developed around a poorly understood structure called Gould’s Belt. In this framework, we use Orion as the template for massive star formation and Taurus for low-mass star formation, but we do not know if these two clouds are related, nor why different clouds have different star formation yields. In this talk I will report the 3-D structure of all local cloud complexes (d < 2kpc), using accurate distances. We find a narrow and coherent 2.7 kpc arrangement of dense gas in the Solar neighborhood that contains many of the clouds thought to be associated with the Gould Belt. This finding is inconsistent with the notion that these clouds are part of a ring, disputing the Gould Belt model. The new structure comprises the majority of nearby star-forming regions, has an aspect ratio of about 1:20, and contains about 3 million solar masses of gas. Remarkably, the new structure appears to be undulating and its 3-D distribution is well described by a damped sinusoidal wave on the plane of the Milky Way, with an average period of about 2 kpc and a maximum amplitude of about 160 pc. Our results represent a first step in the revision of the local gas distribution and offer a new, broader context to studies on the transformation of molecular gas into stars.
Joao Alves (University of Vienna)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Most of what we know about star and planet formation has been secured from spatial 2D observations of the local Galactic neighborhood, collected over the last 70 years. During this time we have established a series of ground truths developed around a poorly understood structure called Gould’s Belt. In this framework, we use Orion as the template for massive star formation and Taurus for low-mass star formation, but we do not know if these two clouds are related, nor why different clouds have different star formation yields. In this talk I will report the 3-D structure of all local cloud complexes (d < 2kpc), using accurate distances. We find a narrow and coherent 2.7 kpc arrangement of dense gas in the Solar neighborhood that contains many of the clouds thought to be associated with the Gould Belt. This finding is inconsistent with the notion that these clouds are part of a ring, disputing the Gould Belt model. The new structure comprises the majority of nearby star-forming regions, has an aspect ratio of about 1:20, and contains about 3 million solar masses of gas. Remarkably, the new structure appears to be undulating and its 3-D distribution is well described by a damped sinusoidal wave on the plane of the Milky Way, with an average period of about 2 kpc and a maximum amplitude of about 160 pc. Our results represent a first step in the revision of the local gas distribution and offer a new, broader context to studies on the transformation of molecular gas into stars.
2019-10-29
16:30
16:30
Dwarf galaxy archaeology: Answering big questions with tiny galaxies
Anna Frebel (MIT)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The first stars and first galaxies formed a few hundred million years after the Big Bang. Their emergence transformed the universe: the first heavy elements changed the gas physics and high energy photons reionized their surroundings. Hence, understanding this early era is at the frontier of modern astrophysics and cosmology. It can be well probed with ancient ultra-faint dwarf galaxies that orbit the Milky Way today. Two ultra-faint dwarf galaxies have been particularly interesting in this regard. Reticulum II is the first known "r-process galaxy". A prolific nucleosynthesis event must have gone off in this system very early on so that subsequent stars formed from gas enriched in large amounts of the very heaviest elements. Calculations for the elemental yield of a neutron star merger match the observed chemical abundances of Reticulum II's stars, thus solving a 60 year old puzzle about the astrophysical site of the rapid (r-) process. Tucana II was recently confirmed to be an extremely metal-poor galaxy ([Fe/H]~-3) with member stars up to 8 half light radii away from the center region. Other systems also contain stars in their outskirts, suggesting that such extended "halos" may not be uncommon among the tinyest dwarf galaxies, possibly being a signature of the very first merger events between galaxies at the earliest times.
Anna Frebel (MIT)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The first stars and first galaxies formed a few hundred million years after the Big Bang. Their emergence transformed the universe: the first heavy elements changed the gas physics and high energy photons reionized their surroundings. Hence, understanding this early era is at the frontier of modern astrophysics and cosmology. It can be well probed with ancient ultra-faint dwarf galaxies that orbit the Milky Way today. Two ultra-faint dwarf galaxies have been particularly interesting in this regard. Reticulum II is the first known "r-process galaxy". A prolific nucleosynthesis event must have gone off in this system very early on so that subsequent stars formed from gas enriched in large amounts of the very heaviest elements. Calculations for the elemental yield of a neutron star merger match the observed chemical abundances of Reticulum II's stars, thus solving a 60 year old puzzle about the astrophysical site of the rapid (r-) process. Tucana II was recently confirmed to be an extremely metal-poor galaxy ([Fe/H]~-3) with member stars up to 8 half light radii away from the center region. Other systems also contain stars in their outskirts, suggesting that such extended "halos" may not be uncommon among the tinyest dwarf galaxies, possibly being a signature of the very first merger events between galaxies at the earliest times.
2019-10-22
16:30
16:30
Fast Radio Bursts: New discoveries and future prospects
Emily Petroff (University of Amsterdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Fast radio bursts (FRBs), bright millisecond duration radio transients, are quickly becoming a subject of intense interest in time-domain astronomy. FRBs have the exciting potential to be used as cosmological probes of both matter and fundamental parameters, but such studies require large populations. Advances in FRB detection using current and next-generation radio telescopes will enable the growth of the population in the next few years from 30 to hundreds. Real-time discovery and follow-up, and new studies of the FRB population will provide us with some of the greatest insights in the coming years. I will discuss many observational aspects of the FRB population, including polarisation, searches for multi-wavelength emission, localisation, and repeating FRBs. I will also discuss how our response to these events can inform next generation surveys and pave the way for the enormous number of FRB discoveries expected in the SKA era.
Emily Petroff (University of Amsterdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Fast radio bursts (FRBs), bright millisecond duration radio transients, are quickly becoming a subject of intense interest in time-domain astronomy. FRBs have the exciting potential to be used as cosmological probes of both matter and fundamental parameters, but such studies require large populations. Advances in FRB detection using current and next-generation radio telescopes will enable the growth of the population in the next few years from 30 to hundreds. Real-time discovery and follow-up, and new studies of the FRB population will provide us with some of the greatest insights in the coming years. I will discuss many observational aspects of the FRB population, including polarisation, searches for multi-wavelength emission, localisation, and repeating FRBs. I will also discuss how our response to these events can inform next generation surveys and pave the way for the enormous number of FRB discoveries expected in the SKA era.
2019-07-23
16:15
16:15
Galactic Magnetism: Past, Present and Future
Sui Ann Mao (Max Planck Inst., Univ. Bonn (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Dynamically important magnetic fields have been shown to play pivotal roles in processes that are closely linked to galaxy evolution. However, how galaxies and their magnetic fields have co-evolved since the early Universe remains an unsolved fundamental question in astro-plasma physics and cosmology. In this talk, I will describe how the advent of broadband radio polarimetry is revolutionizing the field of cosmic magnetism by enabling unambiguous and precise polarization measurements. Then, I will highlight several innovative studies on mapping galactic magnetic fields near and far: from the Milky Way/ nearby galaxies to distant galaxies. I will conclude by discussing the exciting prospects of decoding the origin and evolution of cosmic magnetic fields with Square Kilometre Array pathfinders and the next generation radio telescopes.
Sui Ann Mao (Max Planck Inst., Univ. Bonn (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Dynamically important magnetic fields have been shown to play pivotal roles in processes that are closely linked to galaxy evolution. However, how galaxies and their magnetic fields have co-evolved since the early Universe remains an unsolved fundamental question in astro-plasma physics and cosmology. In this talk, I will describe how the advent of broadband radio polarimetry is revolutionizing the field of cosmic magnetism by enabling unambiguous and precise polarization measurements. Then, I will highlight several innovative studies on mapping galactic magnetic fields near and far: from the Milky Way/ nearby galaxies to distant galaxies. I will conclude by discussing the exciting prospects of decoding the origin and evolution of cosmic magnetic fields with Square Kilometre Array pathfinders and the next generation radio telescopes.
2019-07-16
16:15
16:15
Declining rotation curves, missing baryons, massive clumps and extreme turbulence: the puzzling properties of high-redshift disk galaxies
Andreas Burkert (Dept. Phys., Univ. München (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The redshift 2 universe is one of the most interesting epochs of galaxy evolution. It is the era with the peak of the cosmic star formation rate. Between redshift 3 and 1 the total stellar mass density in galaxies increased fromm15% to 70%. It is also the time of rapid galaxy assembly and the epoch where galaxy morphology was determined. Observations of z=2 star-forming galaxies reveal physical properties that are unparalleled in the z=0 Universe. Gas-rich, extended, fast rotating and highly turbulent disks have been found with star formation rates that are a factor of 10 to 100 larger than in present-day Milky-Way type galaxies. Kpc-sized, massive gas clumps dominate the appearance of these galaxies. Even more interesting are recent observations of declining rotation curves in the outer parts of these disks and dynamical masses, inferred from their rotation velocities that are equal to the observed baryonic mass leaving no room for dark matter. I will summarize the newest observations and the puzzles and challenges that they generate for our theoretical understanding of cosmic galaxy formation and galactic dynamics.
Andreas Burkert (Dept. Phys., Univ. München (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The redshift 2 universe is one of the most interesting epochs of galaxy evolution. It is the era with the peak of the cosmic star formation rate. Between redshift 3 and 1 the total stellar mass density in galaxies increased fromm15% to 70%. It is also the time of rapid galaxy assembly and the epoch where galaxy morphology was determined. Observations of z=2 star-forming galaxies reveal physical properties that are unparalleled in the z=0 Universe. Gas-rich, extended, fast rotating and highly turbulent disks have been found with star formation rates that are a factor of 10 to 100 larger than in present-day Milky-Way type galaxies. Kpc-sized, massive gas clumps dominate the appearance of these galaxies. Even more interesting are recent observations of declining rotation curves in the outer parts of these disks and dynamical masses, inferred from their rotation velocities that are equal to the observed baryonic mass leaving no room for dark matter. I will summarize the newest observations and the puzzles and challenges that they generate for our theoretical understanding of cosmic galaxy formation and galactic dynamics.
2019-07-09
16:15
16:15
Reading physics from stellar spectra
Maria Bergemann (MPIA, Heidelberg (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Stellar spectroscopy is vitally important in many fields of modern astrophysics. The method allows the analysis of fundamental parameters of stars and their chemical composition, the information crucial for studies of stellar physics, star - exoplanet connection, structure and evolution of galaxies. Large surveys, such as WEAVE and 4MOST, will deliver millions of spectra of stars from the most distant corners of the Milky Way. Next-generation gigantic facilities, such as the Extremely Large Telescope (ELT), will observe stars beyond tens of megaparsecs past the Local Group. I will highlight some of the key recent advances in spectroscopy of cool stars. New models of stellar atmospheres and spectra, which account for hydrodynamics and non-local thermodynamic equilibrium, make stars look different and turn classical concepts about stellar physics, origin of the elements, and Galactic evolution upside-down. I will discuss how these developments impact our understanding of stellar explosions and of the Milky Way’s past, in particular, in relation to the emerging field of Galactoseismology. I will also discuss the potential of extragalactic stellar spectroscopy with ELT and present outlook for the future studies.
Maria Bergemann (MPIA, Heidelberg (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Stellar spectroscopy is vitally important in many fields of modern astrophysics. The method allows the analysis of fundamental parameters of stars and their chemical composition, the information crucial for studies of stellar physics, star - exoplanet connection, structure and evolution of galaxies. Large surveys, such as WEAVE and 4MOST, will deliver millions of spectra of stars from the most distant corners of the Milky Way. Next-generation gigantic facilities, such as the Extremely Large Telescope (ELT), will observe stars beyond tens of megaparsecs past the Local Group. I will highlight some of the key recent advances in spectroscopy of cool stars. New models of stellar atmospheres and spectra, which account for hydrodynamics and non-local thermodynamic equilibrium, make stars look different and turn classical concepts about stellar physics, origin of the elements, and Galactic evolution upside-down. I will discuss how these developments impact our understanding of stellar explosions and of the Milky Way’s past, in particular, in relation to the emerging field of Galactoseismology. I will also discuss the potential of extragalactic stellar spectroscopy with ELT and present outlook for the future studies.
2019-07-02
16:15
16:15
Early galaxy formation and its large-scale effects
Pratika Dayal (Univ. Groningen, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Galaxy formation in the first billion years mark a time of great upheaval in the history of the Universe: as the first sources of light, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of cosmic reionization. As the earliest building blocks, the galaxies that formed in the first billion years also determine the physical properties of all subsequent galaxy populations. I will start by introducing the reionization process and detail the reasons foe which the history and topology of reionization remain debated. I will then show how cross-correlations of 21cm data with the underlying galaxy population, in the forthcoming era of 21cm cosmology, will yield tantalising constraints on the average intergalactic medium ionization state as well as the reionization topology (outside-in versus inside-out). Time permitting, I will try to give a flavour of how the assembly of early galaxies, accessible with the forthcoming James Webb Space Telescope, can provide a powerful testbed for Dark Matter models beyond "Cold Dark Matter".
Pratika Dayal (Univ. Groningen, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Galaxy formation in the first billion years mark a time of great upheaval in the history of the Universe: as the first sources of light, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of cosmic reionization. As the earliest building blocks, the galaxies that formed in the first billion years also determine the physical properties of all subsequent galaxy populations. I will start by introducing the reionization process and detail the reasons foe which the history and topology of reionization remain debated. I will then show how cross-correlations of 21cm data with the underlying galaxy population, in the forthcoming era of 21cm cosmology, will yield tantalising constraints on the average intergalactic medium ionization state as well as the reionization topology (outside-in versus inside-out). Time permitting, I will try to give a flavour of how the assembly of early galaxies, accessible with the forthcoming James Webb Space Telescope, can provide a powerful testbed for Dark Matter models beyond "Cold Dark Matter".
2019-06-25
16:15
16:15
Exoplanets around Stars of Different Masses and Evolutionary Stages
Sabine Reffert (LSW, Univ. Heidelberg (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
ith about 4000 extrasolar planets orbiting about 3000 different host stars known today, we are now clearly in the realm of detailed statistical studies of planet and host star properties. Furthermore, rarer systems are found, which sometimes can constrain planet formation and evolution theories single-handedly. Here I will review the main results of two Doppler surveys: the Lick G and K giant survey, focusing on evolved and relatively massive host stars, as well as the Carmenes survey which targets M dwarfs, the least massive host stars. I will discuss both, ensemble properties as well as individual systems, and will summarize what we have learned so far.
Sabine Reffert (LSW, Univ. Heidelberg (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
ith about 4000 extrasolar planets orbiting about 3000 different host stars known today, we are now clearly in the realm of detailed statistical studies of planet and host star properties. Furthermore, rarer systems are found, which sometimes can constrain planet formation and evolution theories single-handedly. Here I will review the main results of two Doppler surveys: the Lick G and K giant survey, focusing on evolved and relatively massive host stars, as well as the Carmenes survey which targets M dwarfs, the least massive host stars. I will discuss both, ensemble properties as well as individual systems, and will summarize what we have learned so far.
2019-06-18
16:15
16:15
Exciting gravitational waves: Messages from merging black holes
Norbert Langer (Argelander Inst., Univ. Bonn, (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Massive black hole merger excite strong gravitational waves that travel throughout the Universe. Currently, about two events per week are being detected. Next to the associated amazing physics of merging black holes and gravitational waves, the question emerges: which astrophysical processes can lead to merging black holes, and which messages are encoded in the five fundamental properties measured in these events (the two masses, spins, and the distance)? An attempt to answer this leads to the physics of stars, supernovae and gamma-ray bursts, star clusters, and high redshift galaxies.
Norbert Langer (Argelander Inst., Univ. Bonn, (D))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Massive black hole merger excite strong gravitational waves that travel throughout the Universe. Currently, about two events per week are being detected. Next to the associated amazing physics of merging black holes and gravitational waves, the question emerges: which astrophysical processes can lead to merging black holes, and which messages are encoded in the five fundamental properties measured in these events (the two masses, spins, and the distance)? An attempt to answer this leads to the physics of stars, supernovae and gamma-ray bursts, star clusters, and high redshift galaxies.
2019-06-11
16:15
16:15
Magnetic fields in neutron stars: from radio pulsars to magnetars
Nanda Rea (Institute of Space Sciences (ICE) Barcelona (Spain))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will review current observational and modelling results on neutron stars with strong magnetic fields (aka magnetars): in particular their outburst activity, their predicted evolution, birth and possible connection with GRBs and SLSNe. Furthermore, I will present new discoveries that strengthen somehow the relation between magnetars and other neutron star classes, and that argue on the ubiquitous presence of strong field non-dipolar component in possibly any young neutron star.
Nanda Rea (Institute of Space Sciences (ICE) Barcelona (Spain))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will review current observational and modelling results on neutron stars with strong magnetic fields (aka magnetars): in particular their outburst activity, their predicted evolution, birth and possible connection with GRBs and SLSNe. Furthermore, I will present new discoveries that strengthen somehow the relation between magnetars and other neutron star classes, and that argue on the ubiquitous presence of strong field non-dipolar component in possibly any young neutron star.
2019-06-04
16:15
16:15
The Multi-Messenger Picture of Neutron Star Mergers
Brian David Metzger (Columbia University, New York (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In 2017 the LIGO/Virgo gravitational wave observatories detected the first binary neutron star merger event (GW170817), a discovery followed by the most ambitious electromagnetic (EM) follow-up campaign ever conducted. Within 2 seconds of the merger, a weak burst of gamma-rays was discovered by the Fermi and INTEGRAL satellites. Within 11 hours, a bright but rapidly-fading thermal optical counterpart was discovered in the galaxy NGC 4993 at a distance of only 130 Million light years. The properties of the optical transient match remarkably well predictions for “kilonova” emission powered by the radioactive decay of heavy nuclei synthesized in the expanding merger ejecta by rapid neutron capture nucleosynthesis (r-process). The rapid spectral evolution of the kilonova emission to near-infrared wavelengths demonstrates that a portion of the ejecta contains heavy lanthanide nuclei. Two weeks after the merger, rising non-thermal X-ray and radio emission were detected from the position of the optical transient, consistent with delayed synchrotron afterglow radiation from an initially off-axis relativistic jet. I will describe efforts to create a unified scenario for the range of EM counterparts from GW170817 and their implications for the astrophysical origin of the r-process and the properties of neutron stars (particularly their uncertain radii and maximum mass, which are determined by the equation of state of dense nuclear matter). Time permitting, I will preview the upcoming era of multi-messenger astronomy, in the current O3 run and once Advanced LIGO/Virgo reach design sensitivity and a neutron star merger is detected every few weeks.
Brian David Metzger (Columbia University, New York (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In 2017 the LIGO/Virgo gravitational wave observatories detected the first binary neutron star merger event (GW170817), a discovery followed by the most ambitious electromagnetic (EM) follow-up campaign ever conducted. Within 2 seconds of the merger, a weak burst of gamma-rays was discovered by the Fermi and INTEGRAL satellites. Within 11 hours, a bright but rapidly-fading thermal optical counterpart was discovered in the galaxy NGC 4993 at a distance of only 130 Million light years. The properties of the optical transient match remarkably well predictions for “kilonova” emission powered by the radioactive decay of heavy nuclei synthesized in the expanding merger ejecta by rapid neutron capture nucleosynthesis (r-process). The rapid spectral evolution of the kilonova emission to near-infrared wavelengths demonstrates that a portion of the ejecta contains heavy lanthanide nuclei. Two weeks after the merger, rising non-thermal X-ray and radio emission were detected from the position of the optical transient, consistent with delayed synchrotron afterglow radiation from an initially off-axis relativistic jet. I will describe efforts to create a unified scenario for the range of EM counterparts from GW170817 and their implications for the astrophysical origin of the r-process and the properties of neutron stars (particularly their uncertain radii and maximum mass, which are determined by the equation of state of dense nuclear matter). Time permitting, I will preview the upcoming era of multi-messenger astronomy, in the current O3 run and once Advanced LIGO/Virgo reach design sensitivity and a neutron star merger is detected every few weeks.
2019-05-28
16:15
16:15
The Story of 1I/’Oumuamua, The First Visitor from Another Star System
Karen Meech (Inst. Astron., Univ. Hawaii (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
On October 19, 2017 the Pan-STARRS1 telescope discovered a rapidly moving object. Additional astrometry obtained with pre-discovery observations on October 18 through data obtained with the Canada-France-Hawaii-Telescope on October 22 showed that the object had the highest hyperbolic eccentricity ever detected, confirming that this object clearly originated from outside the solar system. 1I/2017 U1 passed perihelion on September 9, 2017 and had made its Earth close approach at 63 lunar radii on October 14. The official name of ‘Oumuamua, meaning visitor from the distant past, was approved by the IAU on November 6. Beginning on October 22 there was an intense effort to secure observing resources to characterize the object. Because it was receding rapidly from the Earth and Sun, within a week of discovery the brightness had dropped by a factor of 10 and in less than a month it had dropped by a factor of 100. Thus, there was a period of just over a week where the target could be relatively easily characterized. Deep images of ‘Oumuamua showed no hint of cometary activity, with limits on the amount of dust that could be present at less than 7-8 orders of magnitude that of a typical comet at similar distances. Light curve observations showed that the object was rotating with an instantaneous rotation period of 7.34 hours, and a light curve range of 2.5 magnitudes, implying an extremely elongated axis ratio perhaps as large as 10:1, but certainly larger than 5:1. Spitzer observations suggest an average diameter somewhere between 98-440 km depending on model-dependent surface thermal properties. As more time series data were obtained, it was evident that ‘Oumuamua was in an excited spin state with the long axis precessing around the total angular momentum vector with an average period of 8.67±0.34 hr. The timescale for damping an excited spin in a body this size is very long, so the spin state may reflect the violent process of ejection of ‘Oumuamua from its host planetary system. The color of ‘Oumuamua was found to be quite red with a spectral slope of 23%±3% per 100 nm, consistent with comet surfaces, the dark side of Iapetus, and other minerals. Precision astrometric measurements obtained from the Hubble Space Telescope and the ground allowed us to do a detailed study of the orbit. Analysis of 207 astrometric positions showed that the orbit cannot be fit by a purely gravity-only trajectory, but are well matched (at the 30-sigma level) by the addition of a radial acceleration. We explored several explanations for the non-gravitational motion, and found that cometary outgassing is the most physically plausible, but requires that ‘Oumuamua has a somewhat different nature from solar system comets. Many attempts were made to trace ‘Oumuamua back to it’s home system, the most detailed after the release of the Gaia 2 catalog, but no convincing candidates have been found. Whether this will ever be feasible depends on how long ago it was ejected. ‘Oumuamua has challenged many of our assumptions about what small bodies from another solar system would look like, and has triggered an avalanche of papers, some highly speculative. In this talk I’ll share the story of the discovery of ‘Oumuamua and discuss what we know about our first known interstellar visitor – including new information from papers in press.
Karen Meech (Inst. Astron., Univ. Hawaii (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
On October 19, 2017 the Pan-STARRS1 telescope discovered a rapidly moving object. Additional astrometry obtained with pre-discovery observations on October 18 through data obtained with the Canada-France-Hawaii-Telescope on October 22 showed that the object had the highest hyperbolic eccentricity ever detected, confirming that this object clearly originated from outside the solar system. 1I/2017 U1 passed perihelion on September 9, 2017 and had made its Earth close approach at 63 lunar radii on October 14. The official name of ‘Oumuamua, meaning visitor from the distant past, was approved by the IAU on November 6. Beginning on October 22 there was an intense effort to secure observing resources to characterize the object. Because it was receding rapidly from the Earth and Sun, within a week of discovery the brightness had dropped by a factor of 10 and in less than a month it had dropped by a factor of 100. Thus, there was a period of just over a week where the target could be relatively easily characterized. Deep images of ‘Oumuamua showed no hint of cometary activity, with limits on the amount of dust that could be present at less than 7-8 orders of magnitude that of a typical comet at similar distances. Light curve observations showed that the object was rotating with an instantaneous rotation period of 7.34 hours, and a light curve range of 2.5 magnitudes, implying an extremely elongated axis ratio perhaps as large as 10:1, but certainly larger than 5:1. Spitzer observations suggest an average diameter somewhere between 98-440 km depending on model-dependent surface thermal properties. As more time series data were obtained, it was evident that ‘Oumuamua was in an excited spin state with the long axis precessing around the total angular momentum vector with an average period of 8.67±0.34 hr. The timescale for damping an excited spin in a body this size is very long, so the spin state may reflect the violent process of ejection of ‘Oumuamua from its host planetary system. The color of ‘Oumuamua was found to be quite red with a spectral slope of 23%±3% per 100 nm, consistent with comet surfaces, the dark side of Iapetus, and other minerals. Precision astrometric measurements obtained from the Hubble Space Telescope and the ground allowed us to do a detailed study of the orbit. Analysis of 207 astrometric positions showed that the orbit cannot be fit by a purely gravity-only trajectory, but are well matched (at the 30-sigma level) by the addition of a radial acceleration. We explored several explanations for the non-gravitational motion, and found that cometary outgassing is the most physically plausible, but requires that ‘Oumuamua has a somewhat different nature from solar system comets. Many attempts were made to trace ‘Oumuamua back to it’s home system, the most detailed after the release of the Gaia 2 catalog, but no convincing candidates have been found. Whether this will ever be feasible depends on how long ago it was ejected. ‘Oumuamua has challenged many of our assumptions about what small bodies from another solar system would look like, and has triggered an avalanche of papers, some highly speculative. In this talk I’ll share the story of the discovery of ‘Oumuamua and discuss what we know about our first known interstellar visitor – including new information from papers in press.
2019-05-21
16:15
16:15
Surveying the Physical State of Cold Gas in Nearby Galaxies in the ALMA Era
Adam Leroy (Ohio State University (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Stars form in cold, dense clouds of molecular gas. This gas spans a wide range of density, pressure, composition, and dynamical state, and these properties affect how interacts with the galaxy and forms stars. Until the last few years, surveying this gas in other galaxies has been mostly restricted to coarse inventories, with little information on the physical properties of the gas. As a result, we so far lack a full, observationally-tested theory of cold gas in galaxies that spans cloud formation, star formation, and stellar feedback. Over the last few, the Atacama Large Millimeter/submillimeter Array (ALMA) and upgraded facility like NOEMA have begun to change this situation. I will describe how a new generation of surveys are resolving the physical properties of gas - density, pressure, evolutionary state, and detailed relation to stars and other gas phases - across many galaxies. I will highlight results from the ongoing PHANGS-ALMA survey and the recently completed EMPIRE survey that both show a strong dependence of cold gas properties on host galaxy and dynamical environment within the galaxy.
Adam Leroy (Ohio State University (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Stars form in cold, dense clouds of molecular gas. This gas spans a wide range of density, pressure, composition, and dynamical state, and these properties affect how interacts with the galaxy and forms stars. Until the last few years, surveying this gas in other galaxies has been mostly restricted to coarse inventories, with little information on the physical properties of the gas. As a result, we so far lack a full, observationally-tested theory of cold gas in galaxies that spans cloud formation, star formation, and stellar feedback. Over the last few, the Atacama Large Millimeter/submillimeter Array (ALMA) and upgraded facility like NOEMA have begun to change this situation. I will describe how a new generation of surveys are resolving the physical properties of gas - density, pressure, evolutionary state, and detailed relation to stars and other gas phases - across many galaxies. I will highlight results from the ongoing PHANGS-ALMA survey and the recently completed EMPIRE survey that both show a strong dependence of cold gas properties on host galaxy and dynamical environment within the galaxy.
2019-05-14
16:15
16:15
Planet formation in protoplanetary discs around young stars
Anders Johansen (Lund Observatory (Sweden))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Planets form in protoplanetary discs around young stars as dust and ice particles collide to form larger and larger bodies. I will present a coherent theory framework for the formation of planetary systems. Dust grows to pebbles by coagulation and deposition of volatile ices, but the continued growth to planetesimals is hampered by the poor sticking of mm-cm-sized pebbles. Planetesimals can nevertheless form by gravitational collapse of pebble clumps concentrated in the turbulent gas through the streaming instability. The subsequent growth initially occurs by planetesimal-planetesimal collisions, but the accretion rate of pebbles dominates the growth from 1000-km-sized protoplanets to form the solid cores of gas giants, ice giants and super-Earths. The high growth rates by pebble accretion allow planetary cores to start their growth in much more distant positions than their final orbits. The giant planets orbiting our Sun and other stars can therefore be formed in consistency with planetary migration.
Anders Johansen (Lund Observatory (Sweden))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Planets form in protoplanetary discs around young stars as dust and ice particles collide to form larger and larger bodies. I will present a coherent theory framework for the formation of planetary systems. Dust grows to pebbles by coagulation and deposition of volatile ices, but the continued growth to planetesimals is hampered by the poor sticking of mm-cm-sized pebbles. Planetesimals can nevertheless form by gravitational collapse of pebble clumps concentrated in the turbulent gas through the streaming instability. The subsequent growth initially occurs by planetesimal-planetesimal collisions, but the accretion rate of pebbles dominates the growth from 1000-km-sized protoplanets to form the solid cores of gas giants, ice giants and super-Earths. The high growth rates by pebble accretion allow planetary cores to start their growth in much more distant positions than their final orbits. The giant planets orbiting our Sun and other stars can therefore be formed in consistency with planetary migration.
2019-05-07
16:15
16:15
Advanced optical instrumentation for the characterization of habitable planets, including our own Earth
Frans Snik (Univ. Leiden (NL))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
To directly image and characterize exoplanets, we need advanced optical systems on current and future telescopes that can suppress the bright glare of stars by 6-10 orders of magnitude, and analyze the feeble light of potential planetary companions. Such high-contrast imaging systems consist of advanced adaptive optics and associated wavefront sensing techniques, coronagraphy to (locally) suppress the diffracted starlight, contrast-enhancing techniques like angular/spectral/polarimetric differential imaging, and diagnostic capabilities like (high-resolution) spectroscopy and (spectro)polarimetry. In our group in Leiden we combine all these different aspects of high-contrast imaging, with the aim to achieve the ultimate contrast performance and characterization potential. We are currently exploiting brand-new liquid-crystal technologies that offer important performance benefits for coronagraphy, and for the system as a whole. We have currently installed our “vector-APP” coronagraph at MagAO, LBT, SCExAO, and the stratospheric balloon telescope HiCIBaS, and are developing versions for several other telescopes on the ground and in space. To prepare for our ultimate goal of directly characterizing the atmosphere and surface of a habitable exoplanet and potentially detecting signs of life, we are developing instruments to provide benchmark data for the only planet currently known to harbor life: our own Earth. We have recently performed field measurements of the most compelling biomarker: circular polarization due to homochirality of biological molecules. We are currently building instruments to map biomarkers for our planet as a whole from the ISS and from the moon. As a spin-off of all these activities, we are developing remote-sensing approaches for measuring the pollution in our own atmosphere. The instrument SPEXone, based on our spectropolarimetric technology, has been selected for NASA’s next large Earth-observation satellite to measure the influence of aerosol particles on our climate and health. We have even applied the same technique on smartphones (iSPEX), and are collaborating with an army of citizen scientists to perform measurements of air and water pollution.
Frans Snik (Univ. Leiden (NL))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
To directly image and characterize exoplanets, we need advanced optical systems on current and future telescopes that can suppress the bright glare of stars by 6-10 orders of magnitude, and analyze the feeble light of potential planetary companions. Such high-contrast imaging systems consist of advanced adaptive optics and associated wavefront sensing techniques, coronagraphy to (locally) suppress the diffracted starlight, contrast-enhancing techniques like angular/spectral/polarimetric differential imaging, and diagnostic capabilities like (high-resolution) spectroscopy and (spectro)polarimetry. In our group in Leiden we combine all these different aspects of high-contrast imaging, with the aim to achieve the ultimate contrast performance and characterization potential. We are currently exploiting brand-new liquid-crystal technologies that offer important performance benefits for coronagraphy, and for the system as a whole. We have currently installed our “vector-APP” coronagraph at MagAO, LBT, SCExAO, and the stratospheric balloon telescope HiCIBaS, and are developing versions for several other telescopes on the ground and in space. To prepare for our ultimate goal of directly characterizing the atmosphere and surface of a habitable exoplanet and potentially detecting signs of life, we are developing instruments to provide benchmark data for the only planet currently known to harbor life: our own Earth. We have recently performed field measurements of the most compelling biomarker: circular polarization due to homochirality of biological molecules. We are currently building instruments to map biomarkers for our planet as a whole from the ISS and from the moon. As a spin-off of all these activities, we are developing remote-sensing approaches for measuring the pollution in our own atmosphere. The instrument SPEXone, based on our spectropolarimetric technology, has been selected for NASA’s next large Earth-observation satellite to measure the influence of aerosol particles on our climate and health. We have even applied the same technique on smartphones (iSPEX), and are collaborating with an army of citizen scientists to perform measurements of air and water pollution.
2019-04-30
16:15
16:15
Magnets in the Sky
Bryan M. Gaensler (Dunlap Institute for Astronomy and Astrophysic, Univ. Toronto)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Everywhere we look, the Universe is threaded with magnetism. These magnetic fields are surprisingly organised and coherent, and are vital to many of the fundamental processes that astronomers take for granted. However, the mechanisms that create and then sustain magnetism in the Universe are not understood, in no small part because magnetic fields are usually not directly observable. I will present innovative new observations of radio polarimetry and Faraday rotation, and will explain how these data sets provide a unique view of magnetic fields in the Milky Way, in distant galaxies, and in the intergalactic medium. I will conclude by showcasing the powerful new generation of radio telescopes that are at last fully opening the window to the magnetic Universe.
Bryan M. Gaensler (Dunlap Institute for Astronomy and Astrophysic, Univ. Toronto)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
Everywhere we look, the Universe is threaded with magnetism. These magnetic fields are surprisingly organised and coherent, and are vital to many of the fundamental processes that astronomers take for granted. However, the mechanisms that create and then sustain magnetism in the Universe are not understood, in no small part because magnetic fields are usually not directly observable. I will present innovative new observations of radio polarimetry and Faraday rotation, and will explain how these data sets provide a unique view of magnetic fields in the Milky Way, in distant galaxies, and in the intergalactic medium. I will conclude by showcasing the powerful new generation of radio telescopes that are at last fully opening the window to the magnetic Universe.
2019-02-05
16:15
16:15
Molecular tori, black hole fueling and feedback in nearby AGN
Francoise Combes (Observatoire de Paris (France))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Recent molecular line observations with ALMA in several nearby Seyferts have revealed the existence of molecular tori, and the nature of gas flows at 10-20pc scale. At 100pc scale, or kpc-scale, previous work on gravitational torques had shown that only about one third of Seyfert galaxies experienced molecular inflow and central fueling, while in most cases the gas was stalled in rings. At higher resolution, i.e. 10-20pc scale, it is possible now to see in some cases AGN fueling due to nuclear trailing spirals, influenced by the black hole potential. This brings smoking gun evidence for nuclear fueling. In our sample galaxies, the angular resolution of up to 80mas allows us to reach the BH-zone of influence and the BH mass can be derived more directly than with the M-sigma relation.
Francoise Combes (Observatoire de Paris (France))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Recent molecular line observations with ALMA in several nearby Seyferts have revealed the existence of molecular tori, and the nature of gas flows at 10-20pc scale. At 100pc scale, or kpc-scale, previous work on gravitational torques had shown that only about one third of Seyfert galaxies experienced molecular inflow and central fueling, while in most cases the gas was stalled in rings. At higher resolution, i.e. 10-20pc scale, it is possible now to see in some cases AGN fueling due to nuclear trailing spirals, influenced by the black hole potential. This brings smoking gun evidence for nuclear fueling. In our sample galaxies, the angular resolution of up to 80mas allows us to reach the BH-zone of influence and the BH mass can be derived more directly than with the M-sigma relation.
2019-01-29
16:15
16:15
Formation and properties of galactic discs: The N-body view
Lia Athanassoula (Laboratoire d’Astrophysique de Marseille (France))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
I will use realistic N-body chemo-dynamic simulations to provide understanding about the formation and evolution of galactic discs and of their structures. After a general introduction, I will focus on a few specific points, as e.g. the influence of bars, a comparison of the evolution and properties of the thin and the thick discs, etc. My approach will include not only morphology, kinematics and dynamics, but also stellar populations, defined by their ages and chemical abundances. I will, whenever possible, make comparisons with the Milky Way.
Lia Athanassoula (Laboratoire d’Astrophysique de Marseille (France))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
I will use realistic N-body chemo-dynamic simulations to provide understanding about the formation and evolution of galactic discs and of their structures. After a general introduction, I will focus on a few specific points, as e.g. the influence of bars, a comparison of the evolution and properties of the thin and the thick discs, etc. My approach will include not only morphology, kinematics and dynamics, but also stellar populations, defined by their ages and chemical abundances. I will, whenever possible, make comparisons with the Milky Way.
2019-01-22
16:15
16:15
-- NO COLLOQUIUM --
(speaker got ill) (...)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Because this weeks speaker got ill we have to cancel the colloquium.
(speaker got ill) (...)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
Because this weeks speaker got ill we have to cancel the colloquium.
2019-01-15
16:15
16:15
How can nucleosynthesis constrain explosions? New perspectives using multi-D supernova models
Claudia Travaglio (INAF (Turino))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
During this seminar I will describe my research program aiming at a better understanding of the physics of supernovae and of the origin of nuclei by increasing the quality and predictive power of numerical models as well as nucleosynthesis calculations. Supernovae play essential roles in the frameworks of many branches of astrophysics: star formation, galaxy dynamics, high-energy astrophysics, galactic chemical evolution, and cosmology. In spite of their ubiquitous presence in astrophysics, there are many uncertainties related to progenitor systems, treatment of the explosions, cross section determinations at such high temperatures, and comparisons with spectra. Most popular results in the field of nucleosynthesis during explosions are still mostly based on one-spatial dimension calculations. The pioneering and very innovative aspect today is the possibility of coupling nucleosynthesis to multidimensional simulations of different type of supernovae. I will show recent results and future perspectives in multi-dimensional calculations of thermonuclear as well as core-collapse supernovae, using tracer particle method for nucleosynthesis. I will illustrate detailed comparison of 1D and 3D supernova models with nucleosynthesis calculations and discussing the needs of multi-D (and where it is needed). Despite the huge investments in nuclear physics experiments, theoretical studies establishing priority lists of reactions to be measured and precision required for astrophysics are currently very limited. During this seminar I will also discuss a priority list for future experiments and improvements in predictions of key nuclear reactions for explosive nucleosynthesis. My expertise in Galactic Chemical Evolution modelling lead to the possibility to study a dependence of the SNe yields on metallicity and their contribution over the galactic age up to reproducing the Solar System composition. During my talk I will refer different times to result of chemical evolution studies with the need of a more clear understanding of the impact of supernovae at the earliest stages of the evolution of galaxies, and their contribution to the Solar System composition. The wealth of information from galactic surveys makes this the ideal time for a theorist to understand the formation and evolution of galaxies with a new generation of chemical evolution models. To this goal, at the end of my talk, I will describe a novel project to model chemo-dynamical evolution of the cosmos, based on a N-body SPH RAMSES code making use of the framework on a moving mesh, adjusting automatically spatial resolution but using a large number of isotopes.
Claudia Travaglio (INAF (Turino))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
During this seminar I will describe my research program aiming at a better understanding of the physics of supernovae and of the origin of nuclei by increasing the quality and predictive power of numerical models as well as nucleosynthesis calculations. Supernovae play essential roles in the frameworks of many branches of astrophysics: star formation, galaxy dynamics, high-energy astrophysics, galactic chemical evolution, and cosmology. In spite of their ubiquitous presence in astrophysics, there are many uncertainties related to progenitor systems, treatment of the explosions, cross section determinations at such high temperatures, and comparisons with spectra. Most popular results in the field of nucleosynthesis during explosions are still mostly based on one-spatial dimension calculations. The pioneering and very innovative aspect today is the possibility of coupling nucleosynthesis to multidimensional simulations of different type of supernovae. I will show recent results and future perspectives in multi-dimensional calculations of thermonuclear as well as core-collapse supernovae, using tracer particle method for nucleosynthesis. I will illustrate detailed comparison of 1D and 3D supernova models with nucleosynthesis calculations and discussing the needs of multi-D (and where it is needed). Despite the huge investments in nuclear physics experiments, theoretical studies establishing priority lists of reactions to be measured and precision required for astrophysics are currently very limited. During this seminar I will also discuss a priority list for future experiments and improvements in predictions of key nuclear reactions for explosive nucleosynthesis. My expertise in Galactic Chemical Evolution modelling lead to the possibility to study a dependence of the SNe yields on metallicity and their contribution over the galactic age up to reproducing the Solar System composition. During my talk I will refer different times to result of chemical evolution studies with the need of a more clear understanding of the impact of supernovae at the earliest stages of the evolution of galaxies, and their contribution to the Solar System composition. The wealth of information from galactic surveys makes this the ideal time for a theorist to understand the formation and evolution of galaxies with a new generation of chemical evolution models. To this goal, at the end of my talk, I will describe a novel project to model chemo-dynamical evolution of the cosmos, based on a N-body SPH RAMSES code making use of the framework on a moving mesh, adjusting automatically spatial resolution but using a large number of isotopes.
2019-01-08
16:15
16:15
The IllustrisTNG Project
Lars Hernquist (Harvard-Smithsonian Center for Astrophysics, Cambridge (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
A predictive theory of galaxy formation remains elusive, even after more than 50 years of dedicated effort by many renowned astrophysicists. The problem of galaxy formation is made difficult by the large range in scales involved and the many non-linear physical processes at play. This talk describes a new generation of numerical models that are designed to overcome these difficulties based on novel schemes for solving the fluid equations on a moving mesh. In particular, I will describe an ongoing project that extends results from the Illustris simulation by employing refined models for feedback from stars and supermassive black holes. Several applications will be described, including the color evolution of galaxies, low surface brightness galaxies, and large-scale structure statistics.
Lars Hernquist (Harvard-Smithsonian Center for Astrophysics, Cambridge (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
A predictive theory of galaxy formation remains elusive, even after more than 50 years of dedicated effort by many renowned astrophysicists. The problem of galaxy formation is made difficult by the large range in scales involved and the many non-linear physical processes at play. This talk describes a new generation of numerical models that are designed to overcome these difficulties based on novel schemes for solving the fluid equations on a moving mesh. In particular, I will describe an ongoing project that extends results from the Illustris simulation by employing refined models for feedback from stars and supermassive black holes. Several applications will be described, including the color evolution of galaxies, low surface brightness galaxies, and large-scale structure statistics.
2018-12-18
16:15
16:15
Star formation from kpc to hundreds of AU scales
Henrik Beuther (MPI for Astronomy (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Star formation is a hierarchical process where fragmentation and gas dynamical processes start on the largest galactic scales and continue down to the formation and accretion processes around the protostars. Starting with bar-spiral arm interfaces, then going step-wise to smaller scales of molecular clouds, star-forming regions, cores and potential (massive)accretion disks, I will present recent observational results related to the dynamical processes during cloud and star formation.
Henrik Beuther (MPI for Astronomy (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Star formation is a hierarchical process where fragmentation and gas dynamical processes start on the largest galactic scales and continue down to the formation and accretion processes around the protostars. Starting with bar-spiral arm interfaces, then going step-wise to smaller scales of molecular clouds, star-forming regions, cores and potential (massive)accretion disks, I will present recent observational results related to the dynamical processes during cloud and star formation.
2018-12-11
16:15
16:15
Carbon-enhanced metal-poor stars: probes of first-star nucleosynthesis and galaxy assembly
Timothy C. Beers (University of Notre Dame (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Over the course of the past few decades, it has become clear that the class of metal-poor stars known as carbon-enhanced metal-poor (CEMP) stars are powerful probes of a number of areas of interest to contemporary astrophysics. I review the multiple lines of evidence that demonstrate the association of CEMP-no stars (which do not exhibit neutron-capture element enhancements) with the nucleosynthesis products of the very first stars, their likely birth place in low-mass mini-halos, and (once accreted by the halo) their role as tracers of the outer-halo population of the Galaxy. The CEMP-s stars (which exhibit enhancements of the heavy s-process elements), by contrast, are likely to have been born in more massive mini-halos, and serve as tracers of the inner-halo population. The well-known increasing frequency of CEMP-no stars (and newly recognized relative constancy of CEMP-s stars) with declining metallicity, and the identification of the primary groups in the Yoon-Beers diagram of A(C) vs. [Fe/H], provide the means to explore these associations in more detail, and to constrain numerical models of the formation of the Milky Way.
Timothy C. Beers (University of Notre Dame (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Over the course of the past few decades, it has become clear that the class of metal-poor stars known as carbon-enhanced metal-poor (CEMP) stars are powerful probes of a number of areas of interest to contemporary astrophysics. I review the multiple lines of evidence that demonstrate the association of CEMP-no stars (which do not exhibit neutron-capture element enhancements) with the nucleosynthesis products of the very first stars, their likely birth place in low-mass mini-halos, and (once accreted by the halo) their role as tracers of the outer-halo population of the Galaxy. The CEMP-s stars (which exhibit enhancements of the heavy s-process elements), by contrast, are likely to have been born in more massive mini-halos, and serve as tracers of the inner-halo population. The well-known increasing frequency of CEMP-no stars (and newly recognized relative constancy of CEMP-s stars) with declining metallicity, and the identification of the primary groups in the Yoon-Beers diagram of A(C) vs. [Fe/H], provide the means to explore these associations in more detail, and to constrain numerical models of the formation of the Milky Way.
2018-12-04
16:15
16:15
Evaluating Cosmic Dawn
Anastasia Fialkov (Institute of Astronomy, Cambridge (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Cosmic dawn is one of the least-explored epochs in the history of the Universe illuminated by the very first stars and black holes. 21-cm radio signal produced by the intergalactic neutral hydrogen is tied to the intensity of radiation generated by these first sources of light. The signal can be used to constrain process of primordial star and black hole formation as well as reionization. In my talk I will discuss astrophysical processes that drive the signal. Pioneering radio experiments such as EDGES High-Band and SARASII deliver data which are capable to disfavor large sections of the high-redshift astrophysical parameter space. I will show the first observational constraints on reionization and cosmic dawn derived using the data of global 21-cm experiments at redshifts z~6-14. I will also discuss combined constraints with high-redshift quasars and Lyman Break Galaxies. Finally, I will comment on the claimed detection made with the EDGES Low-Band antenna at z~17.
Anastasia Fialkov (Institute of Astronomy, Cambridge (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Cosmic dawn is one of the least-explored epochs in the history of the Universe illuminated by the very first stars and black holes. 21-cm radio signal produced by the intergalactic neutral hydrogen is tied to the intensity of radiation generated by these first sources of light. The signal can be used to constrain process of primordial star and black hole formation as well as reionization. In my talk I will discuss astrophysical processes that drive the signal. Pioneering radio experiments such as EDGES High-Band and SARASII deliver data which are capable to disfavor large sections of the high-redshift astrophysical parameter space. I will show the first observational constraints on reionization and cosmic dawn derived using the data of global 21-cm experiments at redshifts z~6-14. I will also discuss combined constraints with high-redshift quasars and Lyman Break Galaxies. Finally, I will comment on the claimed detection made with the EDGES Low-Band antenna at z~17.
2018-11-27
16:15
16:15
Asteroid Vesta and Jupiter's formation: an astrochemical tale
Diego Turrini (INAF-IAPS Rom, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The first few millions of years of the life of the Solar System, when the young Sun was surrounded by its protoplanetary disk, is a period extremely difficult to investigate and of which we still know very little. Advancements in theoretical models of planetary formation have highlighted the existence of different paths for the formation of the first generations of solid bodies, starting from different formation environments and resulting in different final properties. In parallel, they also highlighted how the formation of giant planets and their orbital migration played a major role in determining how violent the dynamical and collisional evolution of the young Solar System was. As a result, not only the number of proposed formation scenarios has dramatically increased, but even formation scenarios based on extremely different evolutionary paths appear capable of producing final outcomes quite similar to the current Solar System. Luckily for us asteroid Vesta, one of the two targets of the NASA mission Dawn, offers the key to solve this conundrum. Dawn confirmed Vesta's volcanic crust as the source of a specific family of meteorites, the Howardite-Eucrite-Diogenite meteorites (also known collectively as HEDs) and this 'genetic' link reveals that Vesta is one of the most ancient bodies in the Solar System and witnessed the appearance of its giant planets. Together, the HEDs and Dawn tell us two important facts about Vesta. The first one is that the impacts it experienced over the whole life of the Solar System could not destroy its volcanic crust and expose the underlying mantle. The second one is that the early impacts that occurred when the young crust was still partially molten delivered only limited amounts of exogenous materials, most importantly water and metals, to it. Using the formation of Jupiter as a case study, in this talk I'll show how the joint use of these two pieces of information provides a new astrochemical constraint against which to test and quantitatively compare the different scenarios for the formation of the Solar System and the evolution of its protoplanetary disk. Finally, I'll show how the hindsight gained through the study of the Solar System can be applied to investigating circumstellar disks hosting young giant planets around other stars.
Diego Turrini (INAF-IAPS Rom, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The first few millions of years of the life of the Solar System, when the young Sun was surrounded by its protoplanetary disk, is a period extremely difficult to investigate and of which we still know very little. Advancements in theoretical models of planetary formation have highlighted the existence of different paths for the formation of the first generations of solid bodies, starting from different formation environments and resulting in different final properties. In parallel, they also highlighted how the formation of giant planets and their orbital migration played a major role in determining how violent the dynamical and collisional evolution of the young Solar System was. As a result, not only the number of proposed formation scenarios has dramatically increased, but even formation scenarios based on extremely different evolutionary paths appear capable of producing final outcomes quite similar to the current Solar System. Luckily for us asteroid Vesta, one of the two targets of the NASA mission Dawn, offers the key to solve this conundrum. Dawn confirmed Vesta's volcanic crust as the source of a specific family of meteorites, the Howardite-Eucrite-Diogenite meteorites (also known collectively as HEDs) and this 'genetic' link reveals that Vesta is one of the most ancient bodies in the Solar System and witnessed the appearance of its giant planets. Together, the HEDs and Dawn tell us two important facts about Vesta. The first one is that the impacts it experienced over the whole life of the Solar System could not destroy its volcanic crust and expose the underlying mantle. The second one is that the early impacts that occurred when the young crust was still partially molten delivered only limited amounts of exogenous materials, most importantly water and metals, to it. Using the formation of Jupiter as a case study, in this talk I'll show how the joint use of these two pieces of information provides a new astrochemical constraint against which to test and quantitatively compare the different scenarios for the formation of the Solar System and the evolution of its protoplanetary disk. Finally, I'll show how the hindsight gained through the study of the Solar System can be applied to investigating circumstellar disks hosting young giant planets around other stars.
2018-11-20
16:15
16:15
What sets the stellar initial mass function? Why is it so universal?
Patrick Hennebelle (CEA Saclay (France))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Stars are building blocks of our Universe. They determine its chemical evolution through nuclear synthesis, they host planets and they determine the evolution of galaxies. The characteristics of stars is predominantly determined by their masses. As such the stellar mass spectrum, also called the initial mass function (IMF), is truly a fundamental quantity to understand how our Universe works. A large number of studies have been performed to infer the IMF and it appears strikingly universal. That is to say, even when measured in rather different environments, the IMF presents no or modest variations. This is an intriguing fact as naive expectations would naturally relate the mass spectrum of stars to quantities such as the Jeans mass which depends significantly on the gas density and gas temperature. During the talk I will review some of the ideas that have been proposed to explain the IMF and discuss their success and failure. I will then present a large sets of simulations in which the initial conditions, the thermodynamics and the numerical resolution are all systematically varied. These simulations reveal that the initial conditions determine the power-law part of the IMF while the gas effective equation of state (EOS), which describe the isothermal to adiabatic transition, sets the peak of the stellar distribution. Analytical models are developed and compared with the simulation results. It is argued that the power-law part of the mass spectrum is due to an interplay between gravity and turbulence that determine the mass spectrum of gas reservoirs from which stars built their masses. The peak on the other hand, occurs at a mass which is 5-10 times the mass of the first Larson hydrostatic cores determined by the effective EOS. We propose that the very reason of the IMF weak variability is that the first hydrostatic core and immediate surrounding collapsing envelope are small scale processes which are nearly independent of the large scale environment characteristics. I will finish the talk by discussing remaining issues and suggests a possible "unifying picture".
Patrick Hennebelle (CEA Saclay (France))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
Stars are building blocks of our Universe. They determine its chemical evolution through nuclear synthesis, they host planets and they determine the evolution of galaxies. The characteristics of stars is predominantly determined by their masses. As such the stellar mass spectrum, also called the initial mass function (IMF), is truly a fundamental quantity to understand how our Universe works. A large number of studies have been performed to infer the IMF and it appears strikingly universal. That is to say, even when measured in rather different environments, the IMF presents no or modest variations. This is an intriguing fact as naive expectations would naturally relate the mass spectrum of stars to quantities such as the Jeans mass which depends significantly on the gas density and gas temperature. During the talk I will review some of the ideas that have been proposed to explain the IMF and discuss their success and failure. I will then present a large sets of simulations in which the initial conditions, the thermodynamics and the numerical resolution are all systematically varied. These simulations reveal that the initial conditions determine the power-law part of the IMF while the gas effective equation of state (EOS), which describe the isothermal to adiabatic transition, sets the peak of the stellar distribution. Analytical models are developed and compared with the simulation results. It is argued that the power-law part of the mass spectrum is due to an interplay between gravity and turbulence that determine the mass spectrum of gas reservoirs from which stars built their masses. The peak on the other hand, occurs at a mass which is 5-10 times the mass of the first Larson hydrostatic cores determined by the effective EOS. We propose that the very reason of the IMF weak variability is that the first hydrostatic core and immediate surrounding collapsing envelope are small scale processes which are nearly independent of the large scale environment characteristics. I will finish the talk by discussing remaining issues and suggests a possible "unifying picture".
2018-11-13
16:15
16:15
The growth of spiral galaxies over cosmic time
Richard Tuffs (MPI for Nuclear Physics (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
A growing body of photometric, imaging and spectroscopic measurements of the distant galaxy population over the last decade have led to a concensus that the stars that we see today in the local Universe predominantly formed over the past 10Gyr in rotationally-supported and secularly evolving disk-dominated galaxies. Although this observational picture of the evolution of star formation with cosmic time is now well established, observational constraints on how the growth of galaxian disks is modulated (with respect to the overall evolution of the density of the Universe) by the non-linear growth of the parent dark matter (DM) haloes of galaxies have hitherto been limited to indirect statistical treatments, which moreover have been agnostic to galaxy morphology. After an introductory review, I will present results obtained using the Galaxy And Mass Assembly (GAMA) spectroscopic survey, of the so-called "Main Sequence" (MS) relation between SFR and stellar mass for morphologically-selected disk-dominated galaxies in the local Universe. These results are used to examine how the MS relation depends (at fixed stellar mass) on the mass of the host DM halo, as measured through kinematic and weak lensing data. I will also examine the dependence of the relation on cosmic time over the past Gyr - from which the present-day time-derivative of the light curve of galaxy disks in the UV as a function of their stellar mass will be inferred - and the effect on the MS relation and its scatter of whether a galaxy is a dominant central galaxy or is a satellite orbiting within the halo. The overall picture given by this analysis is one in which the efficiency of the condensation of baryons in the intergalactic medium into stars in galaxy disks as a function of halo mass varies according to a simple time-independent power law relation. Overall, this picture suggests that the present day diversity of the galaxy population, in particular the well-known propensity of red/blue galaxies to inhabit more/less dense regions of the cosmic web, and the rapidity at which the star formation activity of the Universe is being extinguished, is driven mainly by the transformation of morphology from disks to spheroids in different environments, rather than by variations of the cooling and accretion of the intergalactic medium onto galaxies as a function of environment.
Richard Tuffs (MPI for Nuclear Physics (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
A growing body of photometric, imaging and spectroscopic measurements of the distant galaxy population over the last decade have led to a concensus that the stars that we see today in the local Universe predominantly formed over the past 10Gyr in rotationally-supported and secularly evolving disk-dominated galaxies. Although this observational picture of the evolution of star formation with cosmic time is now well established, observational constraints on how the growth of galaxian disks is modulated (with respect to the overall evolution of the density of the Universe) by the non-linear growth of the parent dark matter (DM) haloes of galaxies have hitherto been limited to indirect statistical treatments, which moreover have been agnostic to galaxy morphology. After an introductory review, I will present results obtained using the Galaxy And Mass Assembly (GAMA) spectroscopic survey, of the so-called "Main Sequence" (MS) relation between SFR and stellar mass for morphologically-selected disk-dominated galaxies in the local Universe. These results are used to examine how the MS relation depends (at fixed stellar mass) on the mass of the host DM halo, as measured through kinematic and weak lensing data. I will also examine the dependence of the relation on cosmic time over the past Gyr - from which the present-day time-derivative of the light curve of galaxy disks in the UV as a function of their stellar mass will be inferred - and the effect on the MS relation and its scatter of whether a galaxy is a dominant central galaxy or is a satellite orbiting within the halo. The overall picture given by this analysis is one in which the efficiency of the condensation of baryons in the intergalactic medium into stars in galaxy disks as a function of halo mass varies according to a simple time-independent power law relation. Overall, this picture suggests that the present day diversity of the galaxy population, in particular the well-known propensity of red/blue galaxies to inhabit more/less dense regions of the cosmic web, and the rapidity at which the star formation activity of the Universe is being extinguished, is driven mainly by the transformation of morphology from disks to spheroids in different environments, rather than by variations of the cooling and accretion of the intergalactic medium onto galaxies as a function of environment.
2018-11-06
16:15
16:15
The role of chemistry in the formation of stars
Simon Glover (Center for Astronomy (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The good correlation that is observed in local spiral galaxies between the molecular gas surface density and the star formation rate surface density demonstrates that there is a close connection between the presence of molecular gas and the formation of stars. However, the nature of this connection remains a matter of some debate. Does efficient star formation require the cooling provided by carbon monoxide (CO) and other heavy molecules? Or are they simply good tracers of conditions conducive to star formation? In this talk, I will discuss the role that molecules such as CO play in governing the thermal balance of interstellar gas and present the results of some recent simulations designed to explore the connection between molecular gas and star formation.
Simon Glover (Center for Astronomy (Heidelberg))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The good correlation that is observed in local spiral galaxies between the molecular gas surface density and the star formation rate surface density demonstrates that there is a close connection between the presence of molecular gas and the formation of stars. However, the nature of this connection remains a matter of some debate. Does efficient star formation require the cooling provided by carbon monoxide (CO) and other heavy molecules? Or are they simply good tracers of conditions conducive to star formation? In this talk, I will discuss the role that molecules such as CO play in governing the thermal balance of interstellar gas and present the results of some recent simulations designed to explore the connection between molecular gas and star formation.
2018-10-30
16:15
16:15
H0 and the never-ending story of the expansion rate of the universe
Bruno Leibundgut (ESO Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The uncertainty of the measured Hubble constant (H0) has been reduced by more than a factor of 10 over the past three decades. Despite this significant improvement the discussion on H0 continues unabated. The value of the Hubble constant sets the size and age of the universe. Since H0 is based on an absolute measurement, it is regarded as the most difficult cosmological parameter to determine. In particular, a discrepancy between local determinations of H0 and the ones based on cosmological models has emerged. It has been speculated that if the tension is confirmed an additional cosmological parameter would have to be introduced. The critical measurements of the distance ladder and in particular the use of supernovae as distance indicators will be discussed within this context.
Bruno Leibundgut (ESO Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
The uncertainty of the measured Hubble constant (H0) has been reduced by more than a factor of 10 over the past three decades. Despite this significant improvement the discussion on H0 continues unabated. The value of the Hubble constant sets the size and age of the universe. Since H0 is based on an absolute measurement, it is regarded as the most difficult cosmological parameter to determine. In particular, a discrepancy between local determinations of H0 and the ones based on cosmological models has emerged. It has been speculated that if the tension is confirmed an additional cosmological parameter would have to be introduced. The critical measurements of the distance ladder and in particular the use of supernovae as distance indicators will be discussed within this context.
2018-10-23
16:14
16:14
The photoevaporation of protoplanetary discs
Cathie J. Clarke (Cambridge, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Planets form in dusty discs whose upper layers are bathed in energetic radiation, either deriving from the central star or from massive stars in the local environment. Heating of surface layers can drive powerful winds which can limit the lifetime of discs and their planet forming potential. I will describe some highlights of recent research into disc photoevaporation, emphasising in particular the evidence for substantial photoevaporative losses from environmental heating even in rather sparse birth environments. I will also show how recent studies in OB associations demonstrate that proximity to neighouring OB stars has a significant impact on disc lifetimes and can be used to test theories of disc photoevaporation.
Cathie J. Clarke (Cambridge, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
Planets form in dusty discs whose upper layers are bathed in energetic radiation, either deriving from the central star or from massive stars in the local environment. Heating of surface layers can drive powerful winds which can limit the lifetime of discs and their planet forming potential. I will describe some highlights of recent research into disc photoevaporation, emphasising in particular the evidence for substantial photoevaporative losses from environmental heating even in rather sparse birth environments. I will also show how recent studies in OB associations demonstrate that proximity to neighouring OB stars has a significant impact on disc lifetimes and can be used to test theories of disc photoevaporation.
2018-07-24
16:15
16:15
Models of galaxy formation and evolutions: recent progress and open questions - the view from the GAlaxy Evolution and Assembly (GAEA) model.
Gabriella de Lucia
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the physical mechanisms driving the formation and evolution of galaxies in a cosmological context represents one of the most important yet unresolved questions of modern astrophysics. Different methods have been developed over the years to link the physical properties of galaxies to the dark matter haloes in which they reside. I will give a brief overview of the aims and limits of these methods, with particular emphasis on semi-analytic models of galaxy formation. I will then review recent developments of our model for GAlaxy Evolution and Assembly (GAEA), and discuss the role of various physical processes in shaping the measured evolution of the galaxy stellar mass function and mass metallicity relation. I will overview our recent work to include a treatment for the partition of cold gas in its atomic and molecular gas components, and a variable stellar Initial Mass Function. I will conclude by discussing open problems and future perspectives.
Gabriella de Lucia
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the physical mechanisms driving the formation and evolution of galaxies in a cosmological context represents one of the most important yet unresolved questions of modern astrophysics. Different methods have been developed over the years to link the physical properties of galaxies to the dark matter haloes in which they reside. I will give a brief overview of the aims and limits of these methods, with particular emphasis on semi-analytic models of galaxy formation. I will then review recent developments of our model for GAlaxy Evolution and Assembly (GAEA), and discuss the role of various physical processes in shaping the measured evolution of the galaxy stellar mass function and mass metallicity relation. I will overview our recent work to include a treatment for the partition of cold gas in its atomic and molecular gas components, and a variable stellar Initial Mass Function. I will conclude by discussing open problems and future perspectives.
2018-07-17
16:15
16:15
Protoplanetary disks at high angular resolution
Cornelis P. Dullemond (Institut für theoretische Astrophysik, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
With ALMA and high-contrast optical/IR imaging, protoplanetary disks are revealed to be structured objects. They display rings, spirals, vortices and warps. These structures appear to be extremely well-defined and often have high contrast. This poses the question: what processes cause these conspicuous structures? Are these signs of planet formation? Or do they betray the existence of just-born planets in these disks? In this talk I will discuss these observations and some theoretical models that attempt to explain them. I will show that these structures indicate that dust “pebbles” are being moved around and are trapped in so-called “pressure traps”. I will show that planetary/substellar companions perturb the disk, but that also disk-internal processes can explain some of the ringlike dust traps. Finally I will discuss some ideas to explain the strong warps seen in some of these protoplanetary disks.
Cornelis P. Dullemond (Institut für theoretische Astrophysik, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
With ALMA and high-contrast optical/IR imaging, protoplanetary disks are revealed to be structured objects. They display rings, spirals, vortices and warps. These structures appear to be extremely well-defined and often have high contrast. This poses the question: what processes cause these conspicuous structures? Are these signs of planet formation? Or do they betray the existence of just-born planets in these disks? In this talk I will discuss these observations and some theoretical models that attempt to explain them. I will show that these structures indicate that dust “pebbles” are being moved around and are trapped in so-called “pressure traps”. I will show that planetary/substellar companions perturb the disk, but that also disk-internal processes can explain some of the ringlike dust traps. Finally I will discuss some ideas to explain the strong warps seen in some of these protoplanetary disks.
2018-07-10
16:15
16:15
From the Galaxy to clumps and back again: a tale of star formation from Galactic plane surveys
Sergio Molinari (Inst. Natl. Astrophys., Rome, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Milky Way Galaxy, our home, is a complex ecosystem where a cyclical transformation process brings diffuse barionic matter into dense unstable condensations to form stars, that produce radiant energy for billions of years before releasing chemically enriched material back into the ISM in their final stages of evolution. Star formation is the trigger of this process, eventually driving the evolution of ordinary matter in the Universe from its primordial composition to the present-day chemical diversity necessary for the birth of life. I will present an overview of the Milky Way Galaxy as a star formation engine as painted by the last generation Galactic Plane surveys in continuum and molecular lines. Pivoting around the Herschel Hi-GAL far infrared and submillimeter survey, the multiwavelength Milky Way now offers a complete and statistically significant observational scenario from diffuse ISM clouds, through the pervasive network of filamentary structures, down to the formation of dense clumps and embedded stellar clusters from the individual star formation site to the panoramic view of entire spiral arms. With the VIALACTEA project we organised and analysed these datasets in a unified framework, deploying a homogeneous analysis and classification scheme for nearly 30,000 candidate filamentary structures and more than 100,000 dense clumps with heliocentric distance determinations. We are now able to complete the first resolved map of the Star Formation Rate in the Milky Way and analyse in detail its variation with Galactocentric distance and with respect to spiral arms, as well as in comparison to star formation triggering agents.
Sergio Molinari (Inst. Natl. Astrophys., Rome, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Milky Way Galaxy, our home, is a complex ecosystem where a cyclical transformation process brings diffuse barionic matter into dense unstable condensations to form stars, that produce radiant energy for billions of years before releasing chemically enriched material back into the ISM in their final stages of evolution. Star formation is the trigger of this process, eventually driving the evolution of ordinary matter in the Universe from its primordial composition to the present-day chemical diversity necessary for the birth of life. I will present an overview of the Milky Way Galaxy as a star formation engine as painted by the last generation Galactic Plane surveys in continuum and molecular lines. Pivoting around the Herschel Hi-GAL far infrared and submillimeter survey, the multiwavelength Milky Way now offers a complete and statistically significant observational scenario from diffuse ISM clouds, through the pervasive network of filamentary structures, down to the formation of dense clumps and embedded stellar clusters from the individual star formation site to the panoramic view of entire spiral arms. With the VIALACTEA project we organised and analysed these datasets in a unified framework, deploying a homogeneous analysis and classification scheme for nearly 30,000 candidate filamentary structures and more than 100,000 dense clumps with heliocentric distance determinations. We are now able to complete the first resolved map of the Star Formation Rate in the Milky Way and analyse in detail its variation with Galactocentric distance and with respect to spiral arms, as well as in comparison to star formation triggering agents.
2018-07-03
16:15
16:15
Galaxy Formation and Evolution in 3D
Lisa Kewley (Australian National Univ.)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Tracing matter and chemical elements in the Universe is critical for understanding the formation of the first galaxies, the formation and growth of supermassive black holes, and ultimately the evolution of galaxies like our Milky Way. Throughout the history of the universe, large-scale gas flows have moulded the arms of spiral galaxies, formed the bulges of the most massive galaxies in the universe, fed supermassive black holes in the centers of galaxies, fueled generation upon generation of new stars, and enriched the intergalactic medium with metals. The physics and impact of these processes can now be traced through new efficient, wide-field 3D integral field spectrographs. We use multi-object integral field spectroscopy to build the largest local sample of galaxies with wide 3-dimensional imaging spectroscopy. We combine our local results with insights into the early universe probed through gravitational lensing and adaptive optics. I will present the latest results from our large local and high-z 3D surveys to understand the relationship between gas inflows, galactic-scale outflows, star-formation, chemical enrichment, and active galactic nuclei in galaxies. I will finish by discussing how this field will be transformed in the JWST and ELT era.
Lisa Kewley (Australian National Univ.)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
Tracing matter and chemical elements in the Universe is critical for understanding the formation of the first galaxies, the formation and growth of supermassive black holes, and ultimately the evolution of galaxies like our Milky Way. Throughout the history of the universe, large-scale gas flows have moulded the arms of spiral galaxies, formed the bulges of the most massive galaxies in the universe, fed supermassive black holes in the centers of galaxies, fueled generation upon generation of new stars, and enriched the intergalactic medium with metals. The physics and impact of these processes can now be traced through new efficient, wide-field 3D integral field spectrographs. We use multi-object integral field spectroscopy to build the largest local sample of galaxies with wide 3-dimensional imaging spectroscopy. We combine our local results with insights into the early universe probed through gravitational lensing and adaptive optics. I will present the latest results from our large local and high-z 3D surveys to understand the relationship between gas inflows, galactic-scale outflows, star-formation, chemical enrichment, and active galactic nuclei in galaxies. I will finish by discussing how this field will be transformed in the JWST and ELT era.
2018-06-26
16:15
16:15
Pulsar Winds
John Kirk (Max Planck Institut für Kernphysik, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Pulsar Winds and the nebulae which they energize (PWN) are among the most enigmatic objects in astrophysics. They consist of a relativistic, magnetized, electron-positron plasma that forms a compact cloud surrounding young pulsars. Their nonthermal synchrotron and inverse-Compton emission is detected from the radio band to very high energy (TeV) gamma-rays, where they are the dominant galactic source population. The radio-to-infrared spectra of PWN are flat, indicating a remarkably efficient particle acceleration mechanism, able to transfer most of the system energy into a tiny fraction of particles. Despite decades of research, the mechanism responsible for accelerating these particles has remained elusive, and poses one of the greatest challenges in particle acceleration theory. In this talk I will give an introduction to the physics of pulsar winds, and describe recent work on the acceleration mechanisms thought to be at work. These include not only variants of the well-known first-order Fermi mechanism, but also "inductive acceleration", which may explain the mysterious gamma-ray flares from the Crab Nebula, discovered in 2011 by the Agile and Fermi satellites.
John Kirk (Max Planck Institut für Kernphysik, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Pulsar Winds and the nebulae which they energize (PWN) are among the most enigmatic objects in astrophysics. They consist of a relativistic, magnetized, electron-positron plasma that forms a compact cloud surrounding young pulsars. Their nonthermal synchrotron and inverse-Compton emission is detected from the radio band to very high energy (TeV) gamma-rays, where they are the dominant galactic source population. The radio-to-infrared spectra of PWN are flat, indicating a remarkably efficient particle acceleration mechanism, able to transfer most of the system energy into a tiny fraction of particles. Despite decades of research, the mechanism responsible for accelerating these particles has remained elusive, and poses one of the greatest challenges in particle acceleration theory. In this talk I will give an introduction to the physics of pulsar winds, and describe recent work on the acceleration mechanisms thought to be at work. These include not only variants of the well-known first-order Fermi mechanism, but also "inductive acceleration", which may explain the mysterious gamma-ray flares from the Crab Nebula, discovered in 2011 by the Agile and Fermi satellites.
2018-06-19
16:15
16:15
Interstellar grains analysed by the Cassini and Stardust space missions
Mario Trieloff (Inst. Geowiss., Universität Heidelberg, D)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In 1992 the Ulysses spacecraft detected a stream of interstellar dust grains passing our solar system. The Stardust mission succeeded in collecting and identifying seven particles of likely interstellar origin. They are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from representative models of interstellar dust inferred from astronomical observations and theory, but the relatively large grains found are biased to the high mass tail of the interstellar population and may not be truly representative. In-situ analyses of the Cosmic Dust Analyser on-board the Cassini spacecraft obtained between 2004 and 2013 yielded the first mass spectra of grains from the Local Interstellar Cloud. These 36 interstellar grains can be clearly identified and distinguished from Saturn bound dust by their direction and high velocity, and their mean mass is consistent with the typical ISD size inferred from astronomical observations. Mass spectra and grain dynamics suggest the presence of magnesium-rich grains of silicate and oxide composition, partly with iron inclusions. Major rock-forming elements (magnesium, silicon, iron, and calcium) are present in approximately cosmic abundances, with only small grain-to-grain variations, but sulfur and carbon are depleted. The ISD grains in the solar neighborhood appear to be homogenized, likely by repeated processing in the interstellar medium.
Mario Trieloff (Inst. Geowiss., Universität Heidelberg, D)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In 1992 the Ulysses spacecraft detected a stream of interstellar dust grains passing our solar system. The Stardust mission succeeded in collecting and identifying seven particles of likely interstellar origin. They are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from representative models of interstellar dust inferred from astronomical observations and theory, but the relatively large grains found are biased to the high mass tail of the interstellar population and may not be truly representative. In-situ analyses of the Cosmic Dust Analyser on-board the Cassini spacecraft obtained between 2004 and 2013 yielded the first mass spectra of grains from the Local Interstellar Cloud. These 36 interstellar grains can be clearly identified and distinguished from Saturn bound dust by their direction and high velocity, and their mean mass is consistent with the typical ISD size inferred from astronomical observations. Mass spectra and grain dynamics suggest the presence of magnesium-rich grains of silicate and oxide composition, partly with iron inclusions. Major rock-forming elements (magnesium, silicon, iron, and calcium) are present in approximately cosmic abundances, with only small grain-to-grain variations, but sulfur and carbon are depleted. The ISD grains in the solar neighborhood appear to be homogenized, likely by repeated processing in the interstellar medium.
2018-06-12
16:15
16:15
Multi-Messenger Astronomy with Ultra-High Energy Cosmic Rays
Karl-Heinz Kampert (Bergische Universität Wuppertal, D)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The search for the sources of ultra-high energy cosmic rays (UHECR) is the prime motivation for operating high energy gamma-ray-, neutrino-, and cosmic ray observatories around the globe. Cosmic rays are observed to energies reaching beyond 10^20 eV but their sources cannot be identified easily because cosmic rays suffer deflections in galactic and intergalactic magnetic fields. High energy photons and neutrinos, expected as secondary particles from hadronic interactions at or near the sources, propagate without any deflection and would allow seeing the UHECR sources. However, photons can result also from pure electromagnetic processes and neutrinos did not exhibit any point source, yet. To advance the field, information from the three high energy probes is being combined and more recently, also gravitational waves were added for specific transient sources. In fact, last years first simultaneous observation of gravitational waves and electromagnetic emission from the neutron star merger GW170817 is generally considered the start of multi-messenger astronomy. In this talk, we shall highlight benefits from joint observations and we review some recent results, including the search for neutrinos from the neutron star merger GW170817, the study of cross correlations of neutrinos and UHECR, the first significant observations of anisotropies in the UHECR sky above 8 EeV, and evidence of an excess of arrivals from strong nearby sources at energies above 40 EeV.
Karl-Heinz Kampert (Bergische Universität Wuppertal, D)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The search for the sources of ultra-high energy cosmic rays (UHECR) is the prime motivation for operating high energy gamma-ray-, neutrino-, and cosmic ray observatories around the globe. Cosmic rays are observed to energies reaching beyond 10^20 eV but their sources cannot be identified easily because cosmic rays suffer deflections in galactic and intergalactic magnetic fields. High energy photons and neutrinos, expected as secondary particles from hadronic interactions at or near the sources, propagate without any deflection and would allow seeing the UHECR sources. However, photons can result also from pure electromagnetic processes and neutrinos did not exhibit any point source, yet. To advance the field, information from the three high energy probes is being combined and more recently, also gravitational waves were added for specific transient sources. In fact, last years first simultaneous observation of gravitational waves and electromagnetic emission from the neutron star merger GW170817 is generally considered the start of multi-messenger astronomy. In this talk, we shall highlight benefits from joint observations and we review some recent results, including the search for neutrinos from the neutron star merger GW170817, the study of cross correlations of neutrinos and UHECR, the first significant observations of anisotropies in the UHECR sky above 8 EeV, and evidence of an excess of arrivals from strong nearby sources at energies above 40 EeV.
2018-06-05
16:15
16:15
Molecular interactions in dilute media studied with fast ion beams in the Heidelberg Cryogenic Storage Ring
Andreas Wolf (MPI für Kernphysik, Heidelberg, D)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
A cryogenic electrostatic storage ring, the CSR, has been taken into operation at the Max Planck Institute for Nuclear Physics. With laboratory astrophysics studies as one of its goals, the machine was built to store fast ion beams in extremely high vacuum, screened against terrestrial thermal radiation, and over times reaching up to an hour. Through the few-Kelvin cryogenic environment and the extreme suppression of collisional perturbations, in contrast to other ion-trap arrangements, low-energy molecular excitations (rotation, low-frequency vibrations or isomeric conformations) can evolve freely and thermalize purely by radiation. Controlled interaction is applied to the circulating ions by laser radiation or by merged or crossed particle beams (electrons, neutral atoms). Event-by-event multi-fragment detection, even for neutral products, and the high accuracy of charged-particle current measurements enable reaction cross-section and branching ratio measurements. The presentation focuses on laboratory studies of rotational excitation in small molecular ions and on inelastic collisions of molecular ions with cold electrons (dissociative recombination and collisional (de-)excitation). First experimental results, planned studies on polyatomic species relevant in interstellar and circumstellar media, and further projects to study complex molecular ions will be addressed.
Andreas Wolf (MPI für Kernphysik, Heidelberg, D)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
A cryogenic electrostatic storage ring, the CSR, has been taken into operation at the Max Planck Institute for Nuclear Physics. With laboratory astrophysics studies as one of its goals, the machine was built to store fast ion beams in extremely high vacuum, screened against terrestrial thermal radiation, and over times reaching up to an hour. Through the few-Kelvin cryogenic environment and the extreme suppression of collisional perturbations, in contrast to other ion-trap arrangements, low-energy molecular excitations (rotation, low-frequency vibrations or isomeric conformations) can evolve freely and thermalize purely by radiation. Controlled interaction is applied to the circulating ions by laser radiation or by merged or crossed particle beams (electrons, neutral atoms). Event-by-event multi-fragment detection, even for neutral products, and the high accuracy of charged-particle current measurements enable reaction cross-section and branching ratio measurements. The presentation focuses on laboratory studies of rotational excitation in small molecular ions and on inelastic collisions of molecular ions with cold electrons (dissociative recombination and collisional (de-)excitation). First experimental results, planned studies on polyatomic species relevant in interstellar and circumstellar media, and further projects to study complex molecular ions will be addressed.
2018-05-29
16:15
16:15
The Planck view at the magnetized dusty interstellar medium
Francois Boulanger (Université Paris-Sud, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Observations of Galactic dust are a highlight and a lasting legacy of the Planck space mission. Spectacular images combining the intensity of dust emission with the texture derived from polarization data have received world-wide attention and become part of the general scientific knowledge. Beyond this popular success, the dust maps are an immense step forward for Galactic astrophysics, greatly superseding earlier observations. Planck has provided us with the data needed to statistically characterize the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence. Planck multi-frequency observations have also opened a new perspective on interstellar dust, upsetting existing models. Futrhermore, the astrophysics of dust emission has become inter-connected to a paramount objective of observational cosmology: the quest for curl-like (B-mode) polarization of the cosmic microwave background expected to arise from primordial gravitational waves produced during the inflation era in the very early Universe. I will introduce these science topics and highlight key results and perspectives of on-going research.
Francois Boulanger (Université Paris-Sud, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Observations of Galactic dust are a highlight and a lasting legacy of the Planck space mission. Spectacular images combining the intensity of dust emission with the texture derived from polarization data have received world-wide attention and become part of the general scientific knowledge. Beyond this popular success, the dust maps are an immense step forward for Galactic astrophysics, greatly superseding earlier observations. Planck has provided us with the data needed to statistically characterize the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence. Planck multi-frequency observations have also opened a new perspective on interstellar dust, upsetting existing models. Futrhermore, the astrophysics of dust emission has become inter-connected to a paramount objective of observational cosmology: the quest for curl-like (B-mode) polarization of the cosmic microwave background expected to arise from primordial gravitational waves produced during the inflation era in the very early Universe. I will introduce these science topics and highlight key results and perspectives of on-going research.
2018-05-22
16:15
16:15
Type Ia supernovae: From explosions to cosmology
Kate Maguire (Queens University Belfast, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Type Ia supernovae are the incredibly luminous deaths of white dwarfs in binary systems. They play a vital role in chemical enrichment, galaxy feedback, stellar evolution, as well as being instrumental in the discovery of dark energy. However, what are their progenitor systems, and how they explode, remains a mystery. There is increasing observational evidence that there are multiple ways in which white dwarfs can explode. I will review the status of what we know about the stellar systems that produce Type Ia supernovae, as well as discuss the recently discovered zoo of peculiar transients that are also predicted to result from the explosions of white dwarfs, such as He-shell mergers, tidal disruption events, violent mergers. Distinguishing between these explosion scenarios and understanding their diversity is vital for producing the best samples for future precision measurements of the cosmological parameters.
Kate Maguire (Queens University Belfast, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Type Ia supernovae are the incredibly luminous deaths of white dwarfs in binary systems. They play a vital role in chemical enrichment, galaxy feedback, stellar evolution, as well as being instrumental in the discovery of dark energy. However, what are their progenitor systems, and how they explode, remains a mystery. There is increasing observational evidence that there are multiple ways in which white dwarfs can explode. I will review the status of what we know about the stellar systems that produce Type Ia supernovae, as well as discuss the recently discovered zoo of peculiar transients that are also predicted to result from the explosions of white dwarfs, such as He-shell mergers, tidal disruption events, violent mergers. Distinguishing between these explosion scenarios and understanding their diversity is vital for producing the best samples for future precision measurements of the cosmological parameters.
2018-05-15
16:15
16:15
Pulsating variables as tracers of the galaxy formation.
Giuliana Fiorentino (INAF Bologna, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We will review the role of classical variables crossing the Instability Strip in our understanding of galaxy formation and evolution. We will discuss the fundamental role of photometric surveys of resolved stellar populations in our Galaxy and beyond. We have recently analysed the old stellar populations, as traced by RR Lyrae stars, observed in low density environments such as the Galactic halo and dwarf galaxies surrounding the Milky Way. This investigation has revealed that small satellites can not have had a major role in building up this old component of the Galaxy, whereas the contribution of more massive dwarf galaxies like the Large Magellanic Cloud (LMC) and/or the still merging Sagittarius dwarf spheroidal galaxy can be significant. In the near future thanks to Gaia and to the Large Synoptic Survey Telescope these kind of studies will gain much more detail and will be largely extended to the the outskirts of our Local Group (distances 1Mpc).
Giuliana Fiorentino (INAF Bologna, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We will review the role of classical variables crossing the Instability Strip in our understanding of galaxy formation and evolution. We will discuss the fundamental role of photometric surveys of resolved stellar populations in our Galaxy and beyond. We have recently analysed the old stellar populations, as traced by RR Lyrae stars, observed in low density environments such as the Galactic halo and dwarf galaxies surrounding the Milky Way. This investigation has revealed that small satellites can not have had a major role in building up this old component of the Galaxy, whereas the contribution of more massive dwarf galaxies like the Large Magellanic Cloud (LMC) and/or the still merging Sagittarius dwarf spheroidal galaxy can be significant. In the near future thanks to Gaia and to the Large Synoptic Survey Telescope these kind of studies will gain much more detail and will be largely extended to the the outskirts of our Local Group (distances 1Mpc).
2018-05-08
16:15
16:15
Understanding the solar chromosphere
Jorrit Leenaarts (Department of Astronomy Institute for Solar Physics, Stockholm Univ., SE)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The chromosphere is the interface between the interior of the Sun, where its magnetic field is generated, and the hot outer corona that drives the solar wind and causes space weather. It is difficult to understand: the chromosphere is the interface where the dynamics change from gas-pressure driving to magnetic-force driving, radiation transport changes from optically thick to optically thin, the gas state changes from neutral to ionised and from local thermodynamic equilibrium (LTE) to non-equilibrium conditions, and the MHD approximation is not sufficient to fully describe its physics. In this talk I will give an overview of the major open questions on understanding the solar chromosphere, and dicuss how observations, simulations, and advanced analysis tools can be used to shed light on these questions.
Jorrit Leenaarts (Department of Astronomy Institute for Solar Physics, Stockholm Univ., SE)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The chromosphere is the interface between the interior of the Sun, where its magnetic field is generated, and the hot outer corona that drives the solar wind and causes space weather. It is difficult to understand: the chromosphere is the interface where the dynamics change from gas-pressure driving to magnetic-force driving, radiation transport changes from optically thick to optically thin, the gas state changes from neutral to ionised and from local thermodynamic equilibrium (LTE) to non-equilibrium conditions, and the MHD approximation is not sufficient to fully describe its physics. In this talk I will give an overview of the major open questions on understanding the solar chromosphere, and dicuss how observations, simulations, and advanced analysis tools can be used to shed light on these questions.
2018-04-24
16:15
16:15
Weak lensing by large-scale structure as an accurate probe of cosmology and much more!
Henk Hoekstra (Sterrewacht Leiden, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Weak lensing by large-scale structure is one of the most promising techniques to learn more about the nature of dark energy by mapping the dark matter distribution in the Universe as a function of distance. Weak lensing has also developed into the main tool to determine cluster masses, critical for their use for cosmology, but can also be used to study the dark matter halos of galaxies.I will review the recent progress in this active area of research and discuss the prospects for future projects, such as Euclid.
Henk Hoekstra (Sterrewacht Leiden, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Weak lensing by large-scale structure is one of the most promising techniques to learn more about the nature of dark energy by mapping the dark matter distribution in the Universe as a function of distance. Weak lensing has also developed into the main tool to determine cluster masses, critical for their use for cosmology, but can also be used to study the dark matter halos of galaxies.I will review the recent progress in this active area of research and discuss the prospects for future projects, such as Euclid.
2018-02-06
16:15
16:15
Gravitational-wave emission and their multi-messenger signatures
Alessandra Buonanno (MPI Gravitationsphysik, Potsdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The detection of gravitational waves has opened a new era of scientific discovery, as it permits a new kind of observation of the cosmos, quite different from electromagnetic and particle observations. In this talk I will review the gravitational-wave signals detected up to now by LIGO and Virgo, and discuss the theoretical groundwork that allows to identify and interpret those signals. I will also highlight how those new astronomical messengers are unveiling the properties of the most extreme astrophysical objects in the universe and probe fundamental physics.
Alessandra Buonanno (MPI Gravitationsphysik, Potsdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The detection of gravitational waves has opened a new era of scientific discovery, as it permits a new kind of observation of the cosmos, quite different from electromagnetic and particle observations. In this talk I will review the gravitational-wave signals detected up to now by LIGO and Virgo, and discuss the theoretical groundwork that allows to identify and interpret those signals. I will also highlight how those new astronomical messengers are unveiling the properties of the most extreme astrophysical objects in the universe and probe fundamental physics.
2018-01-30
16:15
16:15
Black holes in the era of gravitational wave astronomy
Frans Pretorius (Perimeter Inst., Princeton, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Black holes are one of the more astonishing predictions of the theory of General Relativity. The Schwarzschild black hole solution was discovered within months of Einstein publishing the field equations of general relativity, though for decades after was regarded more as a mathematical curiosity than a plausible description of any real object in the universe. This began to change in the 1960's, both through theoretical and observational discoveries, and finally in 2015 the LIGO gravitational wave detectors found the first direct evidence for the existence of black holes, having measured a signal consistent with the inspiral and merger of two black holes. In this talk I will give an overview of black holes in general relativity, the LIGO observations, and what we can hope to learn about black holes in the coming decade as a plethora of new data is gathered from ground based gravitational wave detectors, the Event Horizon Telescope, and pulsar timing arrays.
Frans Pretorius (Perimeter Inst., Princeton, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Black holes are one of the more astonishing predictions of the theory of General Relativity. The Schwarzschild black hole solution was discovered within months of Einstein publishing the field equations of general relativity, though for decades after was regarded more as a mathematical curiosity than a plausible description of any real object in the universe. This began to change in the 1960's, both through theoretical and observational discoveries, and finally in 2015 the LIGO gravitational wave detectors found the first direct evidence for the existence of black holes, having measured a signal consistent with the inspiral and merger of two black holes. In this talk I will give an overview of black holes in general relativity, the LIGO observations, and what we can hope to learn about black holes in the coming decade as a plethora of new data is gathered from ground based gravitational wave detectors, the Event Horizon Telescope, and pulsar timing arrays.
2018-01-23
16:15
16:15
The circumgalactic medium of high redshift galaxies in emission
Lutz Wisotzki (Leibniz Institut für Astrophysik, Potsdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I present observations with the MUSE instrument at the ESO-VLT that reveal the ubiquitous presence of extended Ly-alpha emitting envelopes around individual normal (non-AGN) galaxies at redshifts z > 3. These haloes are larger by factors of ~3-20 than the corresponding rest-frame UV continuum sources as seen by HST. Between ~20% and >~95% of the observed total Ly-alpha flux comes from the extended halo component. At the sensitivity level provided by MUSE, a large fraction of the field of view is actually covered with Ly alpha emission from redshifts 3 < z < 6, and I present a spectacular colour image visualising the "Sky in Ly-alpha". Our observations provide direct insights into the spatial distribution of at least partly neutral gas in the circumgalactic medium of low to intermediate mass galaxies at z > 3. I also discuss some implications for the demographics of high-redshift galaxies.
Lutz Wisotzki (Leibniz Institut für Astrophysik, Potsdam)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I present observations with the MUSE instrument at the ESO-VLT that reveal the ubiquitous presence of extended Ly-alpha emitting envelopes around individual normal (non-AGN) galaxies at redshifts z > 3. These haloes are larger by factors of ~3-20 than the corresponding rest-frame UV continuum sources as seen by HST. Between ~20% and >~95% of the observed total Ly-alpha flux comes from the extended halo component. At the sensitivity level provided by MUSE, a large fraction of the field of view is actually covered with Ly alpha emission from redshifts 3 < z < 6, and I present a spectacular colour image visualising the "Sky in Ly-alpha". Our observations provide direct insights into the spatial distribution of at least partly neutral gas in the circumgalactic medium of low to intermediate mass galaxies at z > 3. I also discuss some implications for the demographics of high-redshift galaxies.
2018-01-16
16:15
16:15
Black hole mass growth across cosmic time: Insights from radio surveys
Vernesa Smolcic (Univ. Zagreb)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding how galaxies form and evolve through cosmic time, and how these processes are influenced by active galactic nuclei (AGN) are important goals of modern astrophysics. In this context, “radio-mode AGN feedback” is a regular ingredient in cosmological models, yet from an observational perspective still rather poorly understood. It is considered to be a key feedback mechanism, related to central supermassive black hole mass growth, at work in the latest phases of massive galaxy formation, and controlling the galaxy’s stellar mass build-up. Over the past decades our understanding of radio AGN was significantly advanced by panchromatic look-back sky surveys, and we have recently entered a “golden age” of radio astronomy thanks to upgraded and new facilities delivering now an order of magnitude increase in sensitivity. The VLA-COSMOS 3 GHz Large Project is based on 384 hours of observations with the upgraded, Karl G. Jansky Very Large Array (VLA) at 3 GHz (10 cm) toward the two square degree COSMOS field. The survey, reaching a median rms of 2.3 uJy/beam over the two square degrees at an angular resolution of 0.75′′, contains 10,830 radio sources down to 5 times the rms. It simultaneously provides the largest and deepest radio continuum survey at such angular resolution to-date, bridging the gap between last-generation and next-generation radio surveys. These radio data, in conjunction with the panchromatic COSMOS data sets, allowed us to study the physical properties, composite nature (i.e., star-formation vs. AGN related contributions to the total radio emission of the sources), and cosmic evolution of radio AGN out to a redshift of about 6, which can directly be linked to the radio-mode feedback, as postulated in cosmological models.
Vernesa Smolcic (Univ. Zagreb)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding how galaxies form and evolve through cosmic time, and how these processes are influenced by active galactic nuclei (AGN) are important goals of modern astrophysics. In this context, “radio-mode AGN feedback” is a regular ingredient in cosmological models, yet from an observational perspective still rather poorly understood. It is considered to be a key feedback mechanism, related to central supermassive black hole mass growth, at work in the latest phases of massive galaxy formation, and controlling the galaxy’s stellar mass build-up. Over the past decades our understanding of radio AGN was significantly advanced by panchromatic look-back sky surveys, and we have recently entered a “golden age” of radio astronomy thanks to upgraded and new facilities delivering now an order of magnitude increase in sensitivity. The VLA-COSMOS 3 GHz Large Project is based on 384 hours of observations with the upgraded, Karl G. Jansky Very Large Array (VLA) at 3 GHz (10 cm) toward the two square degree COSMOS field. The survey, reaching a median rms of 2.3 uJy/beam over the two square degrees at an angular resolution of 0.75′′, contains 10,830 radio sources down to 5 times the rms. It simultaneously provides the largest and deepest radio continuum survey at such angular resolution to-date, bridging the gap between last-generation and next-generation radio surveys. These radio data, in conjunction with the panchromatic COSMOS data sets, allowed us to study the physical properties, composite nature (i.e., star-formation vs. AGN related contributions to the total radio emission of the sources), and cosmic evolution of radio AGN out to a redshift of about 6, which can directly be linked to the radio-mode feedback, as postulated in cosmological models.
2018-01-09
16:15
16:15
Nucleosynthesis and the origin of stardust grains
Maria Lugaro (Konkoly Obs., HU)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Sixty years ago the picture of the production of the elements in stars was established with the eight nucleosynthetic processes that still represent the basis of this research field. I will describe the birth of stellar nucleosynthesis, the production of the chemical elements in stars, and the observational constraints coming from stellar spectroscopy and from the laboratory analysis of stardust grains extracted from meteorites, as well as the differences between the two. Finally, I will show how recent progress in the laboratory analysis of extra-terrestrial samples has allowed the discovery of tiny but unmistakable signatures of stellar nucleosynthetic origin even in bulk materials in the Solar System, from the Earth to different types of meteorites. These signatures must have been carried by the original stardust grains and their sorting can potentially give us new information on the evolution of the protoplanetary disk.
Maria Lugaro (Konkoly Obs., HU)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Sixty years ago the picture of the production of the elements in stars was established with the eight nucleosynthetic processes that still represent the basis of this research field. I will describe the birth of stellar nucleosynthesis, the production of the chemical elements in stars, and the observational constraints coming from stellar spectroscopy and from the laboratory analysis of stardust grains extracted from meteorites, as well as the differences between the two. Finally, I will show how recent progress in the laboratory analysis of extra-terrestrial samples has allowed the discovery of tiny but unmistakable signatures of stellar nucleosynthetic origin even in bulk materials in the Solar System, from the Earth to different types of meteorites. These signatures must have been carried by the original stardust grains and their sorting can potentially give us new information on the evolution of the protoplanetary disk.
2017-12-19
16:15
16:15
Cassini at Saturn: Mission accomplished
Tilmann Denk (Univ. Berlin)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Grand Lecture Hall -- NOTE: There will be Glühwein and Cookies before the colloquium!
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Abstract
After two decades of flying through space and more than 13 years orbiting Saturn, the journey of the Cassini spacecraft ended in mid-September with an intended crash into the atmosphere of the ring planet. The months before brought an absolute highlight: In the "Grand Finale" of the mission, Cassini crossed the narrow gap between the rings and the atmosphere of the planet 22 times. What has the spacecraft experienced in these 20 years and especially in the Grand Finale, what have we learned about Saturn, its rings and the numerous moons? After having worked with Cassini throughout its entire journey, I will give you a small insight into the most interesting and exciting events and results, garnished with images of huge storms, complex ring structures, intricate tectonics, Germany-sized seas of methane, water eruption "plumes" hundreds of kilometers high, gigantic mountains, objects that look like flying saucers, or in short: pictures of Saturn, its rings and its moons.
Tilmann Denk (Univ. Berlin)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Grand Lecture Hall -- NOTE: There will be Glühwein and Cookies before the colloquium!
Show/hide abstract
Abstract
After two decades of flying through space and more than 13 years orbiting Saturn, the journey of the Cassini spacecraft ended in mid-September with an intended crash into the atmosphere of the ring planet. The months before brought an absolute highlight: In the "Grand Finale" of the mission, Cassini crossed the narrow gap between the rings and the atmosphere of the planet 22 times. What has the spacecraft experienced in these 20 years and especially in the Grand Finale, what have we learned about Saturn, its rings and the numerous moons? After having worked with Cassini throughout its entire journey, I will give you a small insight into the most interesting and exciting events and results, garnished with images of huge storms, complex ring structures, intricate tectonics, Germany-sized seas of methane, water eruption "plumes" hundreds of kilometers high, gigantic mountains, objects that look like flying saucers, or in short: pictures of Saturn, its rings and its moons.
2017-12-12
16:15
16:15
Charting new physics territories with time-domain astronomy
Ariel Goobar (Univ. Stockholm)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The accelerated expansion of the Universe, attributed to the existence of dark energy, was discovered nearly two decades ago using distance measurements of Type Ia supernovae. To find the supernovae, image differencing was used targeting small parts of the sky, with just several thousand galaxies observed a few weeks apart. Since then, technological advances have allowed us to drastically increase the science reach of time-domain astronomy: the new generation of optical cameras can image the entire observable sky in a single night. We are starting to discover very rare phenomena, and to explore new time scales for transient phenomena, allowing us to chart new physics territories.
Ariel Goobar (Univ. Stockholm)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The accelerated expansion of the Universe, attributed to the existence of dark energy, was discovered nearly two decades ago using distance measurements of Type Ia supernovae. To find the supernovae, image differencing was used targeting small parts of the sky, with just several thousand galaxies observed a few weeks apart. Since then, technological advances have allowed us to drastically increase the science reach of time-domain astronomy: the new generation of optical cameras can image the entire observable sky in a single night. We are starting to discover very rare phenomena, and to explore new time scales for transient phenomena, allowing us to chart new physics territories.
2017-12-05
16:15
16:15
Zooming in on planet-forming zones of disks around young stars
Ewine F. van Dishoeck (Leiden Obs., NL / MPE Garching)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Protoplanetary disks are the birthplaces of planets but the spatial resolution at long wavelengths has so far been insufficient to resolve the critical 5-30 AU region. The Atacama Large Millimeter Array (ALMA) now allows us to zoom in to nearby disks and determine the physical and chemical structure associated with planet formation. This talk will provide examples of recent work on observations and models of protoplanetary disks in various stages of evolution. Surveys of large numbers of disks provide insight into typical masses and sizes, revealing surprisingly weak gas emission. Special attention will be given to transitional disks, which are a subset of disks with evidence for sharp-rimmed cavities (gaps or holes). They are the best candidate sources for harboring just-formed giant planets. ALMA allows imaging of both the gas and dust in these disks, providing constraints on the properties of any young planets. Some prospects for JWST will be mentioned.
Ewine F. van Dishoeck (Leiden Obs., NL / MPE Garching)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Protoplanetary disks are the birthplaces of planets but the spatial resolution at long wavelengths has so far been insufficient to resolve the critical 5-30 AU region. The Atacama Large Millimeter Array (ALMA) now allows us to zoom in to nearby disks and determine the physical and chemical structure associated with planet formation. This talk will provide examples of recent work on observations and models of protoplanetary disks in various stages of evolution. Surveys of large numbers of disks provide insight into typical masses and sizes, revealing surprisingly weak gas emission. Special attention will be given to transitional disks, which are a subset of disks with evidence for sharp-rimmed cavities (gaps or holes). They are the best candidate sources for harboring just-formed giant planets. ALMA allows imaging of both the gas and dust in these disks, providing constraints on the properties of any young planets. Some prospects for JWST will be mentioned.
2017-11-28
16:15
16:15
Exoplanets and the search for extraterrestrial life
Ignas Snellen (Univ. Leiden, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Placing the solar system in the context of other planetary systems is one of the central objectives driving the study of extrasolar planets. One of the most fascinating questions in modern science is whether other life-bearing planets exist. In this talk I will review the current state of the art of exoplanet research and discuss future ways to probe biomarker gases in Earth-like exoplanets that could point to biological activity.
Ignas Snellen (Univ. Leiden, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Placing the solar system in the context of other planetary systems is one of the central objectives driving the study of extrasolar planets. One of the most fascinating questions in modern science is whether other life-bearing planets exist. In this talk I will review the current state of the art of exoplanet research and discuss future ways to probe biomarker gases in Earth-like exoplanets that could point to biological activity.
2017-11-21
16:15
16:15
The chemical composition of globular clusters throughout the Local Group
Søren Larsen (Univ. Nijmegen, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will discuss results from our recent work on the detailed chemistry of globular clusters (GCs) in Local Group galaxies. This work is based on a combination of integrated-light spectroscopy at high resolution and resolved imaging with HST in colour combinations that are sensitive to light-element abundance variations. Through the resolved imaging studies, it is now clear that the abundance anomalies that are the hallmark of multiple stellar populations are not restricted to old GCs, but are also found in LMC/SMC clusters as young as 2 Gyrs. This rules out formation mechanisms that were unique to the high redshift Universe. More generally, we find that GCs in dwarfs are, on average, more metal-poor than those in larger galaxies, although no clusters more metal-poor than [Fe/H]\approx-2.5 have been found so far. Overall, a large fraction of the most metal-poor stars in dwarf galaxies tend to belong to GCs. This has important implications for scenarios that invoke heavy cluster mass loss to account for the large fractions of enriched "second-generation" stars in GCs, as well as for globular cluster disruption and its contribution to the field star populations in halos in general.
Søren Larsen (Univ. Nijmegen, NL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will discuss results from our recent work on the detailed chemistry of globular clusters (GCs) in Local Group galaxies. This work is based on a combination of integrated-light spectroscopy at high resolution and resolved imaging with HST in colour combinations that are sensitive to light-element abundance variations. Through the resolved imaging studies, it is now clear that the abundance anomalies that are the hallmark of multiple stellar populations are not restricted to old GCs, but are also found in LMC/SMC clusters as young as 2 Gyrs. This rules out formation mechanisms that were unique to the high redshift Universe. More generally, we find that GCs in dwarfs are, on average, more metal-poor than those in larger galaxies, although no clusters more metal-poor than [Fe/H]\approx-2.5 have been found so far. Overall, a large fraction of the most metal-poor stars in dwarf galaxies tend to belong to GCs. This has important implications for scenarios that invoke heavy cluster mass loss to account for the large fractions of enriched "second-generation" stars in GCs, as well as for globular cluster disruption and its contribution to the field star populations in halos in general.
2017-11-14
16:15
16:15
Quasars in the epoch of reionization
Fabian Walter (Max Planck Institute for Astronomy, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
A prime objective of observational astrophysics is to characterize the earliest sources in the first Gyr of the universe, and to peer into the cosmic times when the first stars, black holes and galaxies formed. Although galaxy candidates are now identified up to redshifts of about 10, their faintness typically precludes detailed studies of their nature. Quasars, on the other hand, are the most luminous non-transient sources known and can be studied in detail at the earliest cosmic epochs. The discovery and characterization of a statistically significant sample of quasars at z>6 is crucial to study the epoch of reionization. I will present our progress in building such a statistical sample, which led to tripling the number of these quasars in just the last three years. I will discuss the diverse range of physical properties of this quasar sample as well as our follow-up studies from optical to radio wavelengths, including a new quasar at a record redshift (z=7.5). In particular, recent observations with ALMA revealed the presence of far-infrared companions around the quasars, and provide key constraints on the spatially resolved properties of the quasar host galaxies. Through multi-line ALMA spectroscopy we can also derive first constraints on the physical conditions of the interstellar medium in the quasar hosts. I will also discuss the potential of future JWST observations.
Fabian Walter (Max Planck Institute for Astronomy, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
A prime objective of observational astrophysics is to characterize the earliest sources in the first Gyr of the universe, and to peer into the cosmic times when the first stars, black holes and galaxies formed. Although galaxy candidates are now identified up to redshifts of about 10, their faintness typically precludes detailed studies of their nature. Quasars, on the other hand, are the most luminous non-transient sources known and can be studied in detail at the earliest cosmic epochs. The discovery and characterization of a statistically significant sample of quasars at z>6 is crucial to study the epoch of reionization. I will present our progress in building such a statistical sample, which led to tripling the number of these quasars in just the last three years. I will discuss the diverse range of physical properties of this quasar sample as well as our follow-up studies from optical to radio wavelengths, including a new quasar at a record redshift (z=7.5). In particular, recent observations with ALMA revealed the presence of far-infrared companions around the quasars, and provide key constraints on the spatially resolved properties of the quasar host galaxies. Through multi-line ALMA spectroscopy we can also derive first constraints on the physical conditions of the interstellar medium in the quasar hosts. I will also discuss the potential of future JWST observations.
2017-11-07
16:15
16:15
No Colloquium - Higgs Workshop at Phil 12
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Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
2017-10-31
16:15
16:15
No Colloquium - 500 Years of Reformation (public holiday)
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Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
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Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Philosophenweg 12
2017-10-24
16:15
16:15
Quantum mechanics and stellar spectroscopy: towards accurate abundance analysis of late-type stars
Paul Barklem (Univ. Uppsala, Sweden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The measurement of stellar properties such as chemical compositions, masses and ages, through stellar spectra, is a fundamental problem in astrophysics, of importance to many fields (e.g. Galactic archeology, chemical evolution, planetary formation, etc.). I discuss progress in the understanding of atomic collision processes relevant to high-accuracy non-LTE analysis of late-type stellar spectra. In particular, to analyse spectra at accuracies approaching the 1% level, quantum mechanical effects such as electron transfer by tunnelling and spin transfer via the exchange interaction should be accounted for in modelling collision processes involving electrons and hydrogen atoms. Similar processes are also important in the relatively young field of non-LTE analysis of spectra of supernova ejecta, showing even larger effects than in stellar atmospheres.
Paul Barklem (Univ. Uppsala, Sweden)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
The measurement of stellar properties such as chemical compositions, masses and ages, through stellar spectra, is a fundamental problem in astrophysics, of importance to many fields (e.g. Galactic archeology, chemical evolution, planetary formation, etc.). I discuss progress in the understanding of atomic collision processes relevant to high-accuracy non-LTE analysis of late-type stellar spectra. In particular, to analyse spectra at accuracies approaching the 1% level, quantum mechanical effects such as electron transfer by tunnelling and spin transfer via the exchange interaction should be accounted for in modelling collision processes involving electrons and hydrogen atoms. Similar processes are also important in the relatively young field of non-LTE analysis of spectra of supernova ejecta, showing even larger effects than in stellar atmospheres.
2017-07-25
16:15
16:15
The centre of M31
John Magorrian (Oxford Univ., UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
M31 is the nearest large galaxy for which we have a dust-free multi-wavelength picture of its central regions. It presents some puzzles. The inner few parsecs are dominated by a double nucleus, which is most naturally explained by Tremaine's (1995) model of an eccentric disc of old stars around a supermassive black hole. A more recent surprise is the discovery of a very compact cluster of young stars around the black hole. I review ongoing work on the construction of a coherent picture of this system and compare it to the clusters found at the centres of other nearby galaxies.
John Magorrian (Oxford Univ., UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
M31 is the nearest large galaxy for which we have a dust-free multi-wavelength picture of its central regions. It presents some puzzles. The inner few parsecs are dominated by a double nucleus, which is most naturally explained by Tremaine's (1995) model of an eccentric disc of old stars around a supermassive black hole. A more recent surprise is the discovery of a very compact cluster of young stars around the black hole. I review ongoing work on the construction of a coherent picture of this system and compare it to the clusters found at the centres of other nearby galaxies.
2017-07-18
16:15
16:15
Characterising atmospheric turbulence for advanced optical astronomical observations
James Osborn (Durham Univ., UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The next generation of 40 m class Extremely Large Telescopes (ELTs) are currently under construction. These vast instruments will enable new discoveries in all areas of astronomy and push forwards the boundaries of human knowledge. They will look further back in space and time to explore the early universe and shed light on unanswered questions such as dark matter and dark energy. They will discover and characterise extra-solar planets and potentially find habitable, or even inhabited, worlds. To fulfil these ambitious objectives these giant telescopes will be equipped with highly sophisticated adaptive technologies in order to counteract the detrimental effects of the Earth’s atmosphere. The characterisation of atmospheric optical turbulence is critical for advanced optical astronomical observations. This includes using data from Adaptive Optics (AO) systems, dedicated auxiliary instrumentation as well as forecasts from numerical models of the Earth’s atmosphere. Exploiting this hybrid approaches enables us to determine the vertical profile of the turbulence strength, velocity, outer scale as well as the local turbulence contained in the telescope dome. This detailed knowledge is vital for wide-field AO systems which are particularly sensitive to the vertical structure of these atmospheric parameters and for highly-complex systems such as extreme AO, where the varying atmospheric parameters have a significant impact on performance. Atmospheric turbulence characterisation is therefore required for modelling, monitoring and optimising AO instrumentation, enabling efficient operation of current sophisticated instrumentation systems as well as the future Extremely Large Telescopes.
James Osborn (Durham Univ., UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The next generation of 40 m class Extremely Large Telescopes (ELTs) are currently under construction. These vast instruments will enable new discoveries in all areas of astronomy and push forwards the boundaries of human knowledge. They will look further back in space and time to explore the early universe and shed light on unanswered questions such as dark matter and dark energy. They will discover and characterise extra-solar planets and potentially find habitable, or even inhabited, worlds. To fulfil these ambitious objectives these giant telescopes will be equipped with highly sophisticated adaptive technologies in order to counteract the detrimental effects of the Earth’s atmosphere. The characterisation of atmospheric optical turbulence is critical for advanced optical astronomical observations. This includes using data from Adaptive Optics (AO) systems, dedicated auxiliary instrumentation as well as forecasts from numerical models of the Earth’s atmosphere. Exploiting this hybrid approaches enables us to determine the vertical profile of the turbulence strength, velocity, outer scale as well as the local turbulence contained in the telescope dome. This detailed knowledge is vital for wide-field AO systems which are particularly sensitive to the vertical structure of these atmospheric parameters and for highly-complex systems such as extreme AO, where the varying atmospheric parameters have a significant impact on performance. Atmospheric turbulence characterisation is therefore required for modelling, monitoring and optimising AO instrumentation, enabling efficient operation of current sophisticated instrumentation systems as well as the future Extremely Large Telescopes.
2017-07-11
16:15
16:15
The Cosmic Nursery: Growth Spurting Galaxies and Baby Black Holes
Sadegh Khochfar (Univ. Edinburgh, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In my talk I will present and discuss recent results from high-resolution simulations on the formation of the first galaxies and how these influence their environment. I will take a close look at how black holes will be seeded in such an environment and how the escape fraction of ionizing photons from galaxies evolves. Results from these simulations have profound implications for future observational missions with e.g. the James Webb Space Telescope and I will discuss these.
Sadegh Khochfar (Univ. Edinburgh, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In my talk I will present and discuss recent results from high-resolution simulations on the formation of the first galaxies and how these influence their environment. I will take a close look at how black holes will be seeded in such an environment and how the escape fraction of ionizing photons from galaxies evolves. Results from these simulations have profound implications for future observational missions with e.g. the James Webb Space Telescope and I will discuss these.
2017-07-04
16:15
16:15
The Milky Way – evidence for Seyfert activity in the recent past
Joss Bland-Hawthorn (Univ. Sydney, Australia)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Galaxy's supermassive black hole is a hundred times closer than any other massive singularity. It is surrounded by a highly unstable gas disk so why is the black hole so peaceful at the present time? This mystery has led to a flurry of models in order to explain why Sgr A* is radiating far below (1 part in 108) the Eddington accretion limit. But has this always been so? Evidence is gathering that Sgr A* has been far more active in the recent past, on timescales of thousands of years and longer. The bipolar wind discovered by MSX, the Fermi gamma-ray bubbles, the WMAP haze, the positronium flash confirmed by INTEGRAL, are indicative of something truly spectacular in the past. But when and how did this happen? We present new evidence that the Galactic Centre was a full blown "active galaxy" just a few million years ago. We discuss the most likely scenario for this incredible event which can be seen today imprinted across the Galaxy.
Joss Bland-Hawthorn (Univ. Sydney, Australia)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
The Galaxy's supermassive black hole is a hundred times closer than any other massive singularity. It is surrounded by a highly unstable gas disk so why is the black hole so peaceful at the present time? This mystery has led to a flurry of models in order to explain why Sgr A* is radiating far below (1 part in 108) the Eddington accretion limit. But has this always been so? Evidence is gathering that Sgr A* has been far more active in the recent past, on timescales of thousands of years and longer. The bipolar wind discovered by MSX, the Fermi gamma-ray bubbles, the WMAP haze, the positronium flash confirmed by INTEGRAL, are indicative of something truly spectacular in the past. But when and how did this happen? We present new evidence that the Galactic Centre was a full blown "active galaxy" just a few million years ago. We discuss the most likely scenario for this incredible event which can be seen today imprinted across the Galaxy.
2017-06-27
16:15
16:15
IllustrisTNG: The new frontier to understand the co-evolution of dark-matter and galaxies with cosmological simulations of structure formation
Annalisa Pillepich (MPIA, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will describe the numerical efforts to simulate galaxies with the code AREPO across an unprecedented range of halo masses, environments, evolutionary stages and cosmic times. In particular, I will focus on the IllustrisTNG project, a collaboration among Heidelberg, Munich, New York and Boston. There we are aiming to simulate a series of three gravity+magnetohydrodynamics cosmological volumes (50, 100, 300 Mpc a side, respectively) capable of both resolving the inner structures of galaxies as small as the classical dwarfs of the Milky Way, as well as of sampling the large scale structure of the Universe with thousands among groups and clusters of galaxies. I will briefly review what is explicitly and empirically solved in gravity+magnetohydrodynamics simulations for galaxy formation in a cosmological context and what is required and what it means to “successfully” reproduce populations of galaxies which resemble the real ones. I will therefore show preliminary results from the IllustrisTNG simulations, by focusing on the assembly of the most massive structures in the Universe, the build up and characterisation of the faint stellar envelopes around galaxies, the connections of the latter to their host DM haloes, and our theoretical expectations for the distribution of dark matter (DM) and stars on large scales and within galaxies.
Annalisa Pillepich (MPIA, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will describe the numerical efforts to simulate galaxies with the code AREPO across an unprecedented range of halo masses, environments, evolutionary stages and cosmic times. In particular, I will focus on the IllustrisTNG project, a collaboration among Heidelberg, Munich, New York and Boston. There we are aiming to simulate a series of three gravity+magnetohydrodynamics cosmological volumes (50, 100, 300 Mpc a side, respectively) capable of both resolving the inner structures of galaxies as small as the classical dwarfs of the Milky Way, as well as of sampling the large scale structure of the Universe with thousands among groups and clusters of galaxies. I will briefly review what is explicitly and empirically solved in gravity+magnetohydrodynamics simulations for galaxy formation in a cosmological context and what is required and what it means to “successfully” reproduce populations of galaxies which resemble the real ones. I will therefore show preliminary results from the IllustrisTNG simulations, by focusing on the assembly of the most massive structures in the Universe, the build up and characterisation of the faint stellar envelopes around galaxies, the connections of the latter to their host DM haloes, and our theoretical expectations for the distribution of dark matter (DM) and stars on large scales and within galaxies.
2017-06-20
16:15
16:15
On the front of exoplanet modelling: Interior structures and atmospheres
Isabelle Baraffe (Univ. Exeter, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will present recent developments of exoplanet atmospheric dynamics based on state-of-the-art Global Circulation Models and will discuss basic assumptions performed previously in this field, in terms of radiative transfer treatment and of chemistry. I will show the importance of treating consistently non equilibrium chemistry in these atmospheres. I will also present a scenario to explain the radius inflation of hot Jupiters, providing a robust mechanism to explain this puzzle.
Isabelle Baraffe (Univ. Exeter, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will present recent developments of exoplanet atmospheric dynamics based on state-of-the-art Global Circulation Models and will discuss basic assumptions performed previously in this field, in terms of radiative transfer treatment and of chemistry. I will show the importance of treating consistently non equilibrium chemistry in these atmospheres. I will also present a scenario to explain the radius inflation of hot Jupiters, providing a robust mechanism to explain this puzzle.
2017-06-13
16:15
16:15
Studying galaxies in three dimensions
Michele Cappellari (Oxford Univ., UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
For a century, galaxy studies have been based on two-dimensional images and spectra of their energy distribution obtained at a limited number of spatial locations on the galaxies. In the past decade, this kind of observations has been replaced by a new wave of instruments, which are able to obtain spectra at every location over the galaxies, producing a full three-dimensional view. I will give an overview of the new discoveries in our understanding of galaxy formation, produced by this observational revolution.
Michele Cappellari (Oxford Univ., UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
For a century, galaxy studies have been based on two-dimensional images and spectra of their energy distribution obtained at a limited number of spatial locations on the galaxies. In the past decade, this kind of observations has been replaced by a new wave of instruments, which are able to obtain spectra at every location over the galaxies, producing a full three-dimensional view. I will give an overview of the new discoveries in our understanding of galaxy formation, produced by this observational revolution.
2017-06-06
16:15
16:15
Do we understand the cosmic dipole?
Dominik Schwarz (Univ. Bielefeld)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The dipole of the cosmic microwave background (CMB) defines a reference frame for cosmology. Is is assumed since its discovery that the CMB dipole is caused by the proper motion of the Solar system. This hypothesis leads to the prediction that the corresponding Doppler shifts and abberation effects are universal to all frequencies. Thus the CMB frame is assumed to be the comoving frame of freely falling Friedmann observers, which is essential in the analysis of many cosmological observables such as the Hubble diagram. As any fundamental hypothesis, also the proper motion hypothesis must be tested. I present results from a suite of cosmic radio dipole measurements based on radio continuum catalogues across frequencies. We find that the cosmic radio dipole agrees with the direction of the CMB dipole within errors but has an excess in amplitude which increases with wavelength. The limitations and consequences of our finding are discussed.
Dominik Schwarz (Univ. Bielefeld)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The dipole of the cosmic microwave background (CMB) defines a reference frame for cosmology. Is is assumed since its discovery that the CMB dipole is caused by the proper motion of the Solar system. This hypothesis leads to the prediction that the corresponding Doppler shifts and abberation effects are universal to all frequencies. Thus the CMB frame is assumed to be the comoving frame of freely falling Friedmann observers, which is essential in the analysis of many cosmological observables such as the Hubble diagram. As any fundamental hypothesis, also the proper motion hypothesis must be tested. I present results from a suite of cosmic radio dipole measurements based on radio continuum catalogues across frequencies. We find that the cosmic radio dipole agrees with the direction of the CMB dipole within errors but has an excess in amplitude which increases with wavelength. The limitations and consequences of our finding are discussed.
2017-05-30
16:15
16:15
Frontier Problems in the Theory of Exoplanetary Atmospheres
Kevin Heng (Univ. Bern, Switzerland)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The study of the atmospheres of exoplanets has evolved into a frontier topic in astronomy and astrophysics. In principle, these atmospheres encode information on the formation history of exoplanets, their gaseous chemical inventory, and whether they are habitable and/or inhabitable. In practice, there are a series of unsolved theoretical problems that need to be overcome before the promise of exoplanetary atmospheres is fulfilled. In this colloquium, I will review a selected subset of these problems, some of which are active topics of research within my group and research center. As a prelude, I will perform a concise, theorist’s review of the landscape of current and future observations, both from the ground and space. I will then discuss the following 5 problems: degeneracies in transmission spectra, cloudiness, 1D versus 3D models, geochemical cycles and biosignature gases. I will end by performing a concise, executive review of my new textbook (“Exoplanetary Atmospheres: Theoretical Concepts and Foundations”) by Princeton University Press. (The first student who comes up to me after the colloquium and demonstrates that he/she is a student will receive a free copy.)
Kevin Heng (Univ. Bern, Switzerland)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
The study of the atmospheres of exoplanets has evolved into a frontier topic in astronomy and astrophysics. In principle, these atmospheres encode information on the formation history of exoplanets, their gaseous chemical inventory, and whether they are habitable and/or inhabitable. In practice, there are a series of unsolved theoretical problems that need to be overcome before the promise of exoplanetary atmospheres is fulfilled. In this colloquium, I will review a selected subset of these problems, some of which are active topics of research within my group and research center. As a prelude, I will perform a concise, theorist’s review of the landscape of current and future observations, both from the ground and space. I will then discuss the following 5 problems: degeneracies in transmission spectra, cloudiness, 1D versus 3D models, geochemical cycles and biosignature gases. I will end by performing a concise, executive review of my new textbook (“Exoplanetary Atmospheres: Theoretical Concepts and Foundations”) by Princeton University Press. (The first student who comes up to me after the colloquium and demonstrates that he/she is a student will receive a free copy.)
2017-05-23
16:15
16:15
Cosmic Test Ban Violators: Classical Novae across the Spectrum
Steve Shore (Dept. of Physics, Univ. of Pisa; Astron. Inst., Charles Univ. Prague)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
For those whose tastes run to explosions, classical novae are a goldmine of physical processes whose study illuminates a broad range of comic objects: planetary nebulae and luminous blue variables in fast forward, supernovae in slow motion, and lots in between. I'll review some of the results of the last seven years of panchromatic observations and simulations that are the basis of the Nova Legacy Project, a coordinated benchmark study of every known subtype of nova from cm through MeV.
Steve Shore (Dept. of Physics, Univ. of Pisa; Astron. Inst., Charles Univ. Prague)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
For those whose tastes run to explosions, classical novae are a goldmine of physical processes whose study illuminates a broad range of comic objects: planetary nebulae and luminous blue variables in fast forward, supernovae in slow motion, and lots in between. I'll review some of the results of the last seven years of panchromatic observations and simulations that are the basis of the Nova Legacy Project, a coordinated benchmark study of every known subtype of nova from cm through MeV.
2017-05-16
16:15
16:15
Volume-density-driven star formation in the Galaxy
Genevieve Parmentier (ARI, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Properties of star-cluster forming regions are crucial to determining whether nascent clusters emerge of their gaseous cradle as bound entities, or whether they immediately contribute to the field star population. Thanks to the Spitzer, Herschel and Wide-Field Infrared Survey Explorer space telescopes, the characterization of cluster-forming regions has made a major leap forward. In particular, molecular clouds of the Solar neighbourhood have revealed a quadratic star formation relation. We demonstrate that such a star formation relation can be accounted for by a model in which stars form in centrally-concentrated molecular clumps with a constant star formation efficiency per free-fall time. The corresponding model consequences – (i) improved survivability of clusters after the expulsion of the residual star-forming gas, and (ii) smaller stellar age spreads in clusters formed out of higher-density gas -- are discussed. Forging ahead, we also explore the pitfalls which affect the comparison of the star-formation relation for nearby molecular clouds, at low gas surface density, with the star-formation relation for more distant compact molecular clumps, at high gas surface density.
Genevieve Parmentier (ARI, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Properties of star-cluster forming regions are crucial to determining whether nascent clusters emerge of their gaseous cradle as bound entities, or whether they immediately contribute to the field star population. Thanks to the Spitzer, Herschel and Wide-Field Infrared Survey Explorer space telescopes, the characterization of cluster-forming regions has made a major leap forward. In particular, molecular clouds of the Solar neighbourhood have revealed a quadratic star formation relation. We demonstrate that such a star formation relation can be accounted for by a model in which stars form in centrally-concentrated molecular clumps with a constant star formation efficiency per free-fall time. The corresponding model consequences – (i) improved survivability of clusters after the expulsion of the residual star-forming gas, and (ii) smaller stellar age spreads in clusters formed out of higher-density gas -- are discussed. Forging ahead, we also explore the pitfalls which affect the comparison of the star-formation relation for nearby molecular clouds, at low gas surface density, with the star-formation relation for more distant compact molecular clumps, at high gas surface density.
2017-05-09
16:15
16:15
On the rare Stellar Marriages that live happily ever after to eventually merge as Binary Black Holes
Selma de Mink (Univ. Amsterdam, The Netherlands)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Massive stars are nearly always found in close pairs when they are young. A very small fraction of these pairs stay together throughout their turbulent lives. They end their lives as a double black hole system. Their orbit slowly decays until, eventually, they coalesce. These mergers giving rise to such strong bursts of gravitational wave emission that they can be detected directly at earth. The gravitational wave detector LIGO has publicly announced two of such events at the time of writing as well as one candidate event. In this talk I will focus on the lives of the extreme progenitors of LIGO’s black holes and discuss what we are learning about the lives and deaths of the most massive stars.
Selma de Mink (Univ. Amsterdam, The Netherlands)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Massive stars are nearly always found in close pairs when they are young. A very small fraction of these pairs stay together throughout their turbulent lives. They end their lives as a double black hole system. Their orbit slowly decays until, eventually, they coalesce. These mergers giving rise to such strong bursts of gravitational wave emission that they can be detected directly at earth. The gravitational wave detector LIGO has publicly announced two of such events at the time of writing as well as one candidate event. In this talk I will focus on the lives of the extreme progenitors of LIGO’s black holes and discuss what we are learning about the lives and deaths of the most massive stars.
2017-05-02
16:15
16:15
CARMENES: Searching for Blue Planets Orbiting Red Stars
Andreas Quirrenbach (LSW, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
CARMENES is a radial-velocity survey with the 3.5m telescope on Calar Alto looking for terrestrial planets in the habitable zones of 300 nearby M dwarfs. A consortium of eleven German and Spanish institutions built a pair of stabilized high-resolution spectrographs especially for this project. I will explain the scientific and technical considerations underlying the instrument design, show some early science data, and discuss the astronomy program that will be carried out with CARMENES in the coming years.
Andreas Quirrenbach (LSW, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
CARMENES is a radial-velocity survey with the 3.5m telescope on Calar Alto looking for terrestrial planets in the habitable zones of 300 nearby M dwarfs. A consortium of eleven German and Spanish institutions built a pair of stabilized high-resolution spectrographs especially for this project. I will explain the scientific and technical considerations underlying the instrument design, show some early science data, and discuss the astronomy program that will be carried out with CARMENES in the coming years.
2017-04-25
16:15
16:15
Intrinsically aligned galaxies in weak lensing data
Björn Malte Schäfer (ZAH, ITA Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In gravitational lensing one commonly assumes that the intrinsic shapes of galaxies are uncorrelated and that any correlation in the shapes is due to correlated distortion in the weak lensing mapping: But in fact there are tidal interaction mechanisms that can make galaxy shapes intrinsically correlated. In my presentation I will discuss possible tidal interaction and alignment mechanisms for spiral and elliptical galaxies, how the details of the tidal interaction mechanism generates shape correlations as their signature, and how this contribution affects the measurement of cosmological parameters from gravitational lensing. Changing the perspective I will quantify how much about alignment and tidal interaction mechanisms can be learned from weak lensing data and how the two effects can be statistically separated. Finally, I will discuss the role of tidal interaction in the formation of haloes and how tidal interaction changes the mass distribution of haloes.
Björn Malte Schäfer (ZAH, ITA Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
In gravitational lensing one commonly assumes that the intrinsic shapes of galaxies are uncorrelated and that any correlation in the shapes is due to correlated distortion in the weak lensing mapping: But in fact there are tidal interaction mechanisms that can make galaxy shapes intrinsically correlated. In my presentation I will discuss possible tidal interaction and alignment mechanisms for spiral and elliptical galaxies, how the details of the tidal interaction mechanism generates shape correlations as their signature, and how this contribution affects the measurement of cosmological parameters from gravitational lensing. Changing the perspective I will quantify how much about alignment and tidal interaction mechanisms can be learned from weak lensing data and how the two effects can be statistically separated. Finally, I will discuss the role of tidal interaction in the formation of haloes and how tidal interaction changes the mass distribution of haloes.
2017-02-07
17:15
17:15
Gaia 1992-2017: Twenty-five years of kinks & bends - and always uphill.
Ulrich Bastian (Astron. Rechen. Inst., Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will present a few selected aspects of the history and evolution of the Gaia project, from its very start up to its present status, including a short description of last September's "Gaia Data Release 1" and a little preview of the forthcoming, much more dramatic "Gaia Data Release 2". - Summary: Sisyphos is about to finally and definitely deposit his rock on the mountaintop.
Ulrich Bastian (Astron. Rechen. Inst., Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will present a few selected aspects of the history and evolution of the Gaia project, from its very start up to its present status, including a short description of last September's "Gaia Data Release 1" and a little preview of the forthcoming, much more dramatic "Gaia Data Release 2". - Summary: Sisyphos is about to finally and definitely deposit his rock on the mountaintop.
2017-01-31
17:15
17:15
From gas to stars in galaxies
Adrianne Slyz (Univ. Oxford (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Despite differences in their cosmological life stories, galaxies follow a seemingly simple script for star formation: gas transforms itself to stars at a rate which depends on the average gas surface density of a galaxy. For years, galaxy formation simulations have exploited this simple global relationship to make stars, but nature is indicating that more than gas surface density is at play. Turbulence in the star forming gas appears to be key. I will describe the evidence for this and current theoretical ideas of how turbulence shapes star formation. I will then discuss attempts to capture the effect of turbulence on star formation in high resolution cosmological simulations of individual galaxies, which incorporate results from resolved molecular cloud simulations. Consequences for stellar feedback, galaxy mophology, interstellar medium structure and dynamics will be presented.
Adrianne Slyz (Univ. Oxford (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Despite differences in their cosmological life stories, galaxies follow a seemingly simple script for star formation: gas transforms itself to stars at a rate which depends on the average gas surface density of a galaxy. For years, galaxy formation simulations have exploited this simple global relationship to make stars, but nature is indicating that more than gas surface density is at play. Turbulence in the star forming gas appears to be key. I will describe the evidence for this and current theoretical ideas of how turbulence shapes star formation. I will then discuss attempts to capture the effect of turbulence on star formation in high resolution cosmological simulations of individual galaxies, which incorporate results from resolved molecular cloud simulations. Consequences for stellar feedback, galaxy mophology, interstellar medium structure and dynamics will be presented.
2017-01-24
17:15
17:15
Shedding Light on the Dark Cosmos through Gravitational Lensing
Sherry Suyu (MPA, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Gravitational lensing provides powerful means to study dark energy and dark matter in the Universe. In particular, strong lens systems with measured time delays between the multiple images can be used to determine the "time-delay distance" to the lens, which is primarily sensitive to the Hubble constant. Measuring the Hubble constant is crucial for inferring properties of dark energy, spatial curvature of the Universe and neutrino physics. I will describe the ingredients and newly developed techniques for measuring accurately time-delay distances with a realistic account of systematic uncertainties. A program initiated to measure the Hubble constant to <3.5% in precision from gravitational lens time delays is in progress, and I will present the latest results and their implications. An exciting discovery of the first strongly lensed supernova has offered a rare opportunity to perform a true blind test of our modeling techniques. I will show the bright prospects of gravitational lens time delays as an independent and competitive cosmological probe.
Sherry Suyu (MPA, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
Gravitational lensing provides powerful means to study dark energy and dark matter in the Universe. In particular, strong lens systems with measured time delays between the multiple images can be used to determine the "time-delay distance" to the lens, which is primarily sensitive to the Hubble constant. Measuring the Hubble constant is crucial for inferring properties of dark energy, spatial curvature of the Universe and neutrino physics. I will describe the ingredients and newly developed techniques for measuring accurately time-delay distances with a realistic account of systematic uncertainties. A program initiated to measure the Hubble constant to <3.5% in precision from gravitational lens time delays is in progress, and I will present the latest results and their implications. An exciting discovery of the first strongly lensed supernova has offered a rare opportunity to perform a true blind test of our modeling techniques. I will show the bright prospects of gravitational lens time delays as an independent and competitive cosmological probe.
2017-01-17
17:15
17:15
Galactic archaeology to its limits
Else Starkenburg (Leipniz Inst. Astrophys. Potsdam (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The lowest metallicity stars that still exist today probably carry the imprint of very few supernova. As such, they represent our best observational approach to understand the First Stars. In this talk I will review the early (chemical) evolution of the Milky Way system from both modeling and observational perspectives. In particular, I will present results of the Pristine survey, a Franco-Canadian photometric survey of the Milky Way halo designed to efficiently decompose the metallicity structures of the Milky Way halo. I will show how we can use this great discriminatory power to hunt for the very rare extremely metal-poor stars (bearers of the chemical imprint of the first stars), to weed out contaminants around metal-poor dwarf galaxies, and to search for stellar structures in the halo.
Else Starkenburg (Leipniz Inst. Astrophys. Potsdam (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The lowest metallicity stars that still exist today probably carry the imprint of very few supernova. As such, they represent our best observational approach to understand the First Stars. In this talk I will review the early (chemical) evolution of the Milky Way system from both modeling and observational perspectives. In particular, I will present results of the Pristine survey, a Franco-Canadian photometric survey of the Milky Way halo designed to efficiently decompose the metallicity structures of the Milky Way halo. I will show how we can use this great discriminatory power to hunt for the very rare extremely metal-poor stars (bearers of the chemical imprint of the first stars), to weed out contaminants around metal-poor dwarf galaxies, and to search for stellar structures in the halo.
2017-01-10
17:15
17:15
Molecular Gas, Star Formation and Galaxy Dynamics from z~2.5 - 0
Linda Tacconi (MPE, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Comprehensive and systematic studies of star formation and the gas contents of galaxies during the epochs that are associated with the peak (z~1-3), and subsequent winding down (z<1) of star formation in the Universe are enabling us to illustrate the important role that cold gas, the fuel for star formation, has played in the assembly of galaxies across cosmic time. Modest sized surveys already provide robust molecular gas detections in hundreds to a few thousand star forming galaxies (SFGs), from redshifts 0-3. Furthermore, spatially resolved spectroscopy in both the (sub)mm and NIR wavelengths now enable us to study the detailed kinematics, star formation, and ISM properties in SFGs on few kpc scales. I will discuss the results from these surveys, and place them in the general context of galaxy formation and evolution.
Linda Tacconi (MPE, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Comprehensive and systematic studies of star formation and the gas contents of galaxies during the epochs that are associated with the peak (z~1-3), and subsequent winding down (z<1) of star formation in the Universe are enabling us to illustrate the important role that cold gas, the fuel for star formation, has played in the assembly of galaxies across cosmic time. Modest sized surveys already provide robust molecular gas detections in hundreds to a few thousand star forming galaxies (SFGs), from redshifts 0-3. Furthermore, spatially resolved spectroscopy in both the (sub)mm and NIR wavelengths now enable us to study the detailed kinematics, star formation, and ISM properties in SFGs on few kpc scales. I will discuss the results from these surveys, and place them in the general context of galaxy formation and evolution.
2016-12-20
17:15
17:15
Physik, Astronomie und Raumfahrt in Entenhausen (in German)
Stefan Jordan (Astron. Rechen. Inst., Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Anhand einiger von Carl Barks gezeichneter Berichte aus Entenhausen wird geprüft, ob die in unserem Universum gültigen physikalischen Gesetze (z.B. Massenerhaltung, Impulserhaltung, Energieerhaltung, 2. Hauptsatz der Thermodynamik, Gravitationsgesetz) auch auf "Stella Anatium", dem Planeten, auf dem sich Entenhausen befindet, Gültigkeit besitzen. Darüber hinaus wird auf einige Eigenschaften der näheren kosmischen Umgebung von Donald Ducks Heimatplaneten eingegangen, was dadurch erleichtert wird, dass dort Raumfahrt betrieben wird. Der Vortrag wird auf Deutsch gehalten. The talk will be given in German.
Stefan Jordan (Astron. Rechen. Inst., Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Anhand einiger von Carl Barks gezeichneter Berichte aus Entenhausen wird geprüft, ob die in unserem Universum gültigen physikalischen Gesetze (z.B. Massenerhaltung, Impulserhaltung, Energieerhaltung, 2. Hauptsatz der Thermodynamik, Gravitationsgesetz) auch auf "Stella Anatium", dem Planeten, auf dem sich Entenhausen befindet, Gültigkeit besitzen. Darüber hinaus wird auf einige Eigenschaften der näheren kosmischen Umgebung von Donald Ducks Heimatplaneten eingegangen, was dadurch erleichtert wird, dass dort Raumfahrt betrieben wird. Der Vortrag wird auf Deutsch gehalten. The talk will be given in German.
2016-12-13
17:15
17:15
Cosmology with Clusters of Galaxies
Jochen Weller (LMU, München (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Jochen Weller (LMU, München (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
2016-12-06
17:15
17:15
ALMA studies of dust-obscured starbursts in the distant Universe
Ian Smail (Inst. Computational Cosmology, Durham Univ. (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
For more than two decades we have known of the existence of a population of very dusty, far-infrared luminous sources at high redshift. But until the commissioning of ALMA, many of the basic characteristics of these sources were unclear. I will discuss recent studies with ALMA which are beginning to penetrate the obscuration in these systems to allow us to understand their fundamental properties. I will also discuss their connection to the formation and evolution of the galaxy populations we see in the Universe today.
Ian Smail (Inst. Computational Cosmology, Durham Univ. (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
For more than two decades we have known of the existence of a population of very dusty, far-infrared luminous sources at high redshift. But until the commissioning of ALMA, many of the basic characteristics of these sources were unclear. I will discuss recent studies with ALMA which are beginning to penetrate the obscuration in these systems to allow us to understand their fundamental properties. I will also discuss their connection to the formation and evolution of the galaxy populations we see in the Universe today.
2016-11-29
17:15
17:15
Exoplanets@SAC: System architectures of exoplanet systems
Simon Albrecht (MIT, Cambridge (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Over the last twenty years astronomers have discovered thousands of planets orbiting other stars than our sun. Many of these exoplanets display characteristics very different from the planets in our own solar system. Among these are planets on very eccentric (highly elliptical) and highly inclined (oblique) orbits. At Aarhus University one of our research foci is on getting a better understanding of these characteristics by measuring the system architectures for systems ranging from hot-Jupiters to systems with mall multiple planets. I will explain our techniques and present some recent highlights. We also started studying planets showing Transit Timing Variations (TTV). Here we focus on systems which had not been fully characterized by the Kepler mission due to Kepler's limited life time. These systems we now continue to monitor using ground based telescopes.
Simon Albrecht (MIT, Cambridge (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Over the last twenty years astronomers have discovered thousands of planets orbiting other stars than our sun. Many of these exoplanets display characteristics very different from the planets in our own solar system. Among these are planets on very eccentric (highly elliptical) and highly inclined (oblique) orbits. At Aarhus University one of our research foci is on getting a better understanding of these characteristics by measuring the system architectures for systems ranging from hot-Jupiters to systems with mall multiple planets. I will explain our techniques and present some recent highlights. We also started studying planets showing Transit Timing Variations (TTV). Here we focus on systems which had not been fully characterized by the Kepler mission due to Kepler's limited life time. These systems we now continue to monitor using ground based telescopes.
2016-11-22
17:15
17:15
Unveiling the structure of planet-forming disks
Misato Fukagawa (Natl. Astron Obs. Japan, Osawa (Japan))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I present the images of protoplanetary disks around intermediate-mass stars with ages of a few to several million years, collected from Subaru and ALMA. Disk spatial/density structure is an important key to understand how disks evolve possibly under mutual interaction with new-born planets. In our near-infrared observations, rich structures have been uncovered such as radial gaps and spiral arms in remnant envelopes or disks. The strong non-axisymmetry has also been found with ALMA in dust continuum for a few disks with wide gaps, suggesting localized accumulation of dust particles. Although the sample size is still very small (~10), gaps and non-axisymmetry seem common, implying that the significant fraction of disks harbor stellar/planetary-mass companions, or planet-forming activity is already triggered.
Misato Fukagawa (Natl. Astron Obs. Japan, Osawa (Japan))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I present the images of protoplanetary disks around intermediate-mass stars with ages of a few to several million years, collected from Subaru and ALMA. Disk spatial/density structure is an important key to understand how disks evolve possibly under mutual interaction with new-born planets. In our near-infrared observations, rich structures have been uncovered such as radial gaps and spiral arms in remnant envelopes or disks. The strong non-axisymmetry has also been found with ALMA in dust continuum for a few disks with wide gaps, suggesting localized accumulation of dust particles. Although the sample size is still very small (~10), gaps and non-axisymmetry seem common, implying that the significant fraction of disks harbor stellar/planetary-mass companions, or planet-forming activity is already triggered.
2016-11-15
17:15
17:15
The Galactic Centre: a template for understanding star formation and feedback in a high-pressure environment
Steve Longmore (John Moores Univ., Liverpool (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The unknown physics of star formation and feedback represent the main bottleneck in connecting the observable galaxy population to cold dark matter cosmology. Both physical processes are expected to vary strongly with galactic environment and across cosmic history. I will discuss recent progress in understanding the physics of star formation and feedback in the inner few hundred pc of the Milky Way — the Central Molecular Zone (CMZ) — an environment with gas properties very similar to those in starbursts and high-z galaxies, in which most stars in the Universe formed. Within our lifetime, the CMZ is the only such environment for which it will be possible to simultaneously resolve the gas properties down to the size scales of individual (forming) stars, while also tracing galactic-scale processes, making it a critical benchmark for studies of star formation, feedback, and the interstellar medium across cosmic time. I will focus on recent work seeking to explain a puzzling observational paradox: the vast majority of gas in the CMZ is underproducing stars by 1-2 orders of magnitude compared to empirical star formation relations and theoretical predictions, and yet at the same time a very small fraction of the gas is producing the most violent star formation events in the Galaxy. I will discuss the implications of these findings for environmentally (in)dependent star formation relations and theories. I will finish by outlining the details of a model linking the emerging, multi-scale picture of star formation and feedback to a more general understanding of the mass flows and energy cycles in galactic nuclei.
Steve Longmore (John Moores Univ., Liverpool (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The unknown physics of star formation and feedback represent the main bottleneck in connecting the observable galaxy population to cold dark matter cosmology. Both physical processes are expected to vary strongly with galactic environment and across cosmic history. I will discuss recent progress in understanding the physics of star formation and feedback in the inner few hundred pc of the Milky Way — the Central Molecular Zone (CMZ) — an environment with gas properties very similar to those in starbursts and high-z galaxies, in which most stars in the Universe formed. Within our lifetime, the CMZ is the only such environment for which it will be possible to simultaneously resolve the gas properties down to the size scales of individual (forming) stars, while also tracing galactic-scale processes, making it a critical benchmark for studies of star formation, feedback, and the interstellar medium across cosmic time. I will focus on recent work seeking to explain a puzzling observational paradox: the vast majority of gas in the CMZ is underproducing stars by 1-2 orders of magnitude compared to empirical star formation relations and theoretical predictions, and yet at the same time a very small fraction of the gas is producing the most violent star formation events in the Galaxy. I will discuss the implications of these findings for environmentally (in)dependent star formation relations and theories. I will finish by outlining the details of a model linking the emerging, multi-scale picture of star formation and feedback to a more general understanding of the mass flows and energy cycles in galactic nuclei.
2016-11-08
17:15
17:15
Weak Gravitational Lensing by Large-Scale Structure
Hendrik Hildebrandt (Argelander Inst. Astron., Bonn)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Gravitational lensing represents a unique tool to study the dark Universe. In the weak lensing regime small distortions in the images of galaxies caused by the large-scale structure can be detected over the whole sky. Measuring these coherent distortions yields cosmological insights complementary to other probes like the cosmic microwave background (CMB). Ongoing wide-field imaging surveys exploit this to come up with competitive constraints on important cosmological parameters. In this colloquium I will concentrate on recent results from the ongoing European Kilo Degree Survey (KiDS) and show a mild tension of these results with CMB measurements from the Planck mission. Possible future developments will be discussed that could help make cosmic shear measurements even more robust and lead to an answer to the question whether this tension is real or not. I will conclude with an outlook towards future missions like Euclid, LSST, and WFIRST.
Hendrik Hildebrandt (Argelander Inst. Astron., Bonn)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Gravitational lensing represents a unique tool to study the dark Universe. In the weak lensing regime small distortions in the images of galaxies caused by the large-scale structure can be detected over the whole sky. Measuring these coherent distortions yields cosmological insights complementary to other probes like the cosmic microwave background (CMB). Ongoing wide-field imaging surveys exploit this to come up with competitive constraints on important cosmological parameters. In this colloquium I will concentrate on recent results from the ongoing European Kilo Degree Survey (KiDS) and show a mild tension of these results with CMB measurements from the Planck mission. Possible future developments will be discussed that could help make cosmic shear measurements even more robust and lead to an answer to the question whether this tension is real or not. I will conclude with an outlook towards future missions like Euclid, LSST, and WFIRST.
2016-10-25
17:15
17:15
Cosmic Ray Feedback: Written on the Wind
Ellen Zweibel (Univ. Wisconsin-Madison (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Cosmic rays account for about 1/3 of the energy density in the interstellar medium of the Milky Way, and affect interstellar gas dynamics and thermodynamics significantly. Detection and modeling of nonthermal radio and gamma-ray emission from other galaxies and from galaxy clusters is making it possible to measure this fraction remotely and to test theories of cosmic ray acceleration and transport in other environments. I will discuss how cosmic rays are coupled to the ambient medium, assess where extensions of the coupling theory are needed, and show that the nature of cosmic ray coupling matters to the stability of interstellar gas and in driving galactic winds.
Ellen Zweibel (Univ. Wisconsin-Madison (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Cosmic rays account for about 1/3 of the energy density in the interstellar medium of the Milky Way, and affect interstellar gas dynamics and thermodynamics significantly. Detection and modeling of nonthermal radio and gamma-ray emission from other galaxies and from galaxy clusters is making it possible to measure this fraction remotely and to test theories of cosmic ray acceleration and transport in other environments. I will discuss how cosmic rays are coupled to the ambient medium, assess where extensions of the coupling theory are needed, and show that the nature of cosmic ray coupling matters to the stability of interstellar gas and in driving galactic winds.
2016-07-26
17:15
17:15
How cosmic rays shape galaxies
Christoph Pfrommer (HITS, Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the physics of galaxy formation is arguably among the most complicated problems in modern astrophysics. Recent cosmological simulations have demonstrated that feedback by star formation, supernovae and active galactic nuclei appears to be critical in obtaining realistic disk galaxies, to slow down star formation to the small observed rates, and to move gas and metals out of galaxies into the intergalactic medium. However the particular physical processes underlying these feedback processes still remain elusive. In particular, these simulations neglected cosmic rays and magnetic fields, which provide a comparable pressure support in comparison to turbulence in our Galaxy, and are known to couple dynamically and thermally to the gas. I will present our recent efforts to model cosmic ray physics in the cosmological simulation code AREPO and demonstrate that cosmic rays matter on all scales relevant for galaxy formation. Diffusive shock acceleration of cosmic rays at supernova remnants modifies the expansion velocity of the shock wave and the inclusion of cosmic-ray physics in models of the interstellar medium allows for self-regulated outflows from the star-forming disk. I will also present global simulations of galaxy formation that couple cosmic rays to the magneto-hydrodynamics and demonstrate how powerful galactic winds can be launched which reduces the available amount of gas for star formation. Finally, I will discuss the non-thermal radio and gamma-ray emission of Milky-Way like galaxies and how the next-generation instruments such as SKA and CTA can be used to infer properties relevant for galaxy formation.
Christoph Pfrommer (HITS, Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the physics of galaxy formation is arguably among the most complicated problems in modern astrophysics. Recent cosmological simulations have demonstrated that feedback by star formation, supernovae and active galactic nuclei appears to be critical in obtaining realistic disk galaxies, to slow down star formation to the small observed rates, and to move gas and metals out of galaxies into the intergalactic medium. However the particular physical processes underlying these feedback processes still remain elusive. In particular, these simulations neglected cosmic rays and magnetic fields, which provide a comparable pressure support in comparison to turbulence in our Galaxy, and are known to couple dynamically and thermally to the gas. I will present our recent efforts to model cosmic ray physics in the cosmological simulation code AREPO and demonstrate that cosmic rays matter on all scales relevant for galaxy formation. Diffusive shock acceleration of cosmic rays at supernova remnants modifies the expansion velocity of the shock wave and the inclusion of cosmic-ray physics in models of the interstellar medium allows for self-regulated outflows from the star-forming disk. I will also present global simulations of galaxy formation that couple cosmic rays to the magneto-hydrodynamics and demonstrate how powerful galactic winds can be launched which reduces the available amount of gas for star formation. Finally, I will discuss the non-thermal radio and gamma-ray emission of Milky-Way like galaxies and how the next-generation instruments such as SKA and CTA can be used to infer properties relevant for galaxy formation.
2016-07-19
17:15
17:15
Dust evolution in the interstellar medium and the influence of dust on the dynamics in protoplanetary disks
Melanie Koehler (QMUL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Dust grains play a crucial role in many physical and chemical processes in the interstellar medium (ISM) and in protoplanetary disks (PPDs). In the ISM, dust properties influence, for example, the formation and temperature of the major molecules in molecular clouds. It is therefore important to characterise the grain size, structure, shape and material composition in all phases of the ISM. Observations of the dust SED and extinction give indication of the dust properties and how these properties change towards denser regions. Compared to the diffuse ISM the observed SEDs of these denser regions show a decrease in colour temperature, increase in spectral index and increase in emissivity at 250 μm. Based on the THEMIS dust model, these observations can be explained self-consistently with coagulation and accretion processes of dust in regions with Av<16. These evolutionary processes can also explain the observed core- and cloud-shine. In conclusion, the evolutionary processes and especially grain growth begins in denser regions of the ISM. The dynamics of PPDs depend on the chemistry and ionisation rate of the disk which is influenced by the abundance and properties of dust particles. Assuming different approaches to calculate the X-ray (and UV) ionisation rate and different chemical reaction networks including dust particles, the electron abundance and subsequently the Elsasser number are derived. The calculations show that non-ideal magnetohydrodynamic effects dominate the disk interior in the early stage of the disk and that dust growth and dust settling can lead to turbulences in the disk. The calculations further show that dust settling is strongly dependent on the properties of the dust particles.
Melanie Koehler (QMUL)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Dust grains play a crucial role in many physical and chemical processes in the interstellar medium (ISM) and in protoplanetary disks (PPDs). In the ISM, dust properties influence, for example, the formation and temperature of the major molecules in molecular clouds. It is therefore important to characterise the grain size, structure, shape and material composition in all phases of the ISM. Observations of the dust SED and extinction give indication of the dust properties and how these properties change towards denser regions. Compared to the diffuse ISM the observed SEDs of these denser regions show a decrease in colour temperature, increase in spectral index and increase in emissivity at 250 μm. Based on the THEMIS dust model, these observations can be explained self-consistently with coagulation and accretion processes of dust in regions with Av<16. These evolutionary processes can also explain the observed core- and cloud-shine. In conclusion, the evolutionary processes and especially grain growth begins in denser regions of the ISM. The dynamics of PPDs depend on the chemistry and ionisation rate of the disk which is influenced by the abundance and properties of dust particles. Assuming different approaches to calculate the X-ray (and UV) ionisation rate and different chemical reaction networks including dust particles, the electron abundance and subsequently the Elsasser number are derived. The calculations show that non-ideal magnetohydrodynamic effects dominate the disk interior in the early stage of the disk and that dust growth and dust settling can lead to turbulences in the disk. The calculations further show that dust settling is strongly dependent on the properties of the dust particles.
2016-07-12
17:15
17:15
The Era of Large-Scale Cosmological Simulations: exploring large and small scales simultaneously
Mark Vogelsberger (MIT, Dept. Phys., Cambridge, MA (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Progress in our understanding of galaxy formation, improved numerical algorithms, and increased computing power have recently lead to a number of impressive large-scale hydrodynamical simulations, which are able to reproduce key observables of the local and higher redshift Universe. These simulations allow us, for the first time, to study the interplay between large-scale structure and galaxy formation in detail. I will present recent results of these efforts and discuss some successes and failures of them.
Mark Vogelsberger (MIT, Dept. Phys., Cambridge, MA (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Progress in our understanding of galaxy formation, improved numerical algorithms, and increased computing power have recently lead to a number of impressive large-scale hydrodynamical simulations, which are able to reproduce key observables of the local and higher redshift Universe. These simulations allow us, for the first time, to study the interplay between large-scale structure and galaxy formation in detail. I will present recent results of these efforts and discuss some successes and failures of them.
2016-07-05
17:15
17:15
Supermassive Black Holes: Feeding and Feedback
Andrew King (University of Leicester, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The centre of almost every galaxy contains a supermassive black hole. I review recent progress in understanding how this black hole influences its host galaxy, and how it gained its mass.
Andrew King (University of Leicester, UK)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The centre of almost every galaxy contains a supermassive black hole. I review recent progress in understanding how this black hole influences its host galaxy, and how it gained its mass.
2016-06-28
17:15
17:15
A theoretical and computational challenge: learning about the Dark Universe from cosmological linear perturbations.
Julien Lesgourgues (Inst. for Theo. Particle Phys. and Cosmology, Aachen (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Several recent progress on the theoretical side suggest that the Dark Matter, Dark Energy and maybe Dark Radiation sectors could have a richer phenomenology than expected a decade ago, and affect the evolution of cosmological perturbations in non-trivial ways, even on linear scales. To make the best use of current and future data, one needs to face several theoretical and computational challenges, not only at the level of N-body simulations, but also as far as linear scale simulations and data fitting are concerned. I will illustrate this with a few example, picked up especially in the Dark Matter sector.
Julien Lesgourgues (Inst. for Theo. Particle Phys. and Cosmology, Aachen (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Several recent progress on the theoretical side suggest that the Dark Matter, Dark Energy and maybe Dark Radiation sectors could have a richer phenomenology than expected a decade ago, and affect the evolution of cosmological perturbations in non-trivial ways, even on linear scales. To make the best use of current and future data, one needs to face several theoretical and computational challenges, not only at the level of N-body simulations, but also as far as linear scale simulations and data fitting are concerned. I will illustrate this with a few example, picked up especially in the Dark Matter sector.
2016-06-21
17:15
17:15
From large to small scales and back: the challenges of computational cosmology and galaxy formation
Romain Teyssier (Univ. Zürich (Switzerland))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Computing the universe has been a very successful activity over the past decades. We have now entered the era of precision cosmology, and N body simulations have to face new challenges to be able to contribute to the discovery of new physics in the universe. On smaller scales, baryons play an important role, and our understanding of galaxy formation still remains very vague. Feedback processes play an fundamental role in setting up galaxy properties and how they impact their environment. Recently, galaxy formation simulations have gained complexity and realism, introducing new simulated processes like magnetic fields and radiation fields. Our hope is to shed light on fundamental processes in galaxy formation, and to estimate how they will feedback on the mater distribution on large scale, leading to a more accurate, unbiased measurements of dark matter and dark energy properties.
Romain Teyssier (Univ. Zürich (Switzerland))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Computing the universe has been a very successful activity over the past decades. We have now entered the era of precision cosmology, and N body simulations have to face new challenges to be able to contribute to the discovery of new physics in the universe. On smaller scales, baryons play an important role, and our understanding of galaxy formation still remains very vague. Feedback processes play an fundamental role in setting up galaxy properties and how they impact their environment. Recently, galaxy formation simulations have gained complexity and realism, introducing new simulated processes like magnetic fields and radiation fields. Our hope is to shed light on fundamental processes in galaxy formation, and to estimate how they will feedback on the mater distribution on large scale, leading to a more accurate, unbiased measurements of dark matter and dark energy properties.
2016-06-14
17:15
17:15
Space-Based Microlensing: From Planets to Black Holes
Andrew Gould (Ohio State, USA & MPIA Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Space-based microlensing was first proposed 50 years ago as means to measure the "microlens parallax" effect and so derive the distances to the lenses, which are usually unseen. However, it is only in the last 2 years that this idea has been implemented, first using Spitzer and then Kepler, with the aims of measuring the Galactic distribution of planets and measuring the properties of free floating planets, respectively. These campaigns have required radically new approaches to space-based observations and have already led to surprising discoveries unrelated to planets. Preparations are well under way for WFIRST, which will be roughly 25% devoted to microlensing. WFIRST will revolutionize our understanding of planets. Even though it is 100 times closer to Earth than Spitzer and Kepler, it will still yield microlens parallaxes. Using the subtle effects of astrometric microlensing, WFIRST will provide the first census of isolated black holes as well.
Andrew Gould (Ohio State, USA & MPIA Heidelberg)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Space-based microlensing was first proposed 50 years ago as means to measure the "microlens parallax" effect and so derive the distances to the lenses, which are usually unseen. However, it is only in the last 2 years that this idea has been implemented, first using Spitzer and then Kepler, with the aims of measuring the Galactic distribution of planets and measuring the properties of free floating planets, respectively. These campaigns have required radically new approaches to space-based observations and have already led to surprising discoveries unrelated to planets. Preparations are well under way for WFIRST, which will be roughly 25% devoted to microlensing. WFIRST will revolutionize our understanding of planets. Even though it is 100 times closer to Earth than Spitzer and Kepler, it will still yield microlens parallaxes. Using the subtle effects of astrometric microlensing, WFIRST will provide the first census of isolated black holes as well.
2016-06-07
17:15
17:15
Gravitationally imaging dark matter with strong gravitational lensing
Simona Vegetti (MPA, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The cold dark matter (CDM) paradigm predicts that the dark matter haloes of galaxies are populated by a significant number of substructures, with a steeply rising mass function towards lower masses. In the Milky Way, however, of order 10^5 substructures are predicted inside the virial radius, whereas only a few have been so far observed. This poses a major challenge to the CDM paradigm. New and independent methods are, therefore, required to assess the level of mass substructure in galaxies in the Local Universe and beyond. Unfortunately, most of these small mass substructures are expected to be completely dark and therefore not directly observable. Strong gravitational lensing provides a unique opportunity to detect and quantify the smallest and faintest substructures at cosmological distances. Thanks to the combination of state-of-the art lens modelling tools and high angular resolution data, we are now able to probe the substructure mass function at a new low mass limit, where competing dark matter models differ by more than two orders of magnitudes. In this talk I will present the latest results and future perspective of substructure lensing.
Simona Vegetti (MPA, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The cold dark matter (CDM) paradigm predicts that the dark matter haloes of galaxies are populated by a significant number of substructures, with a steeply rising mass function towards lower masses. In the Milky Way, however, of order 10^5 substructures are predicted inside the virial radius, whereas only a few have been so far observed. This poses a major challenge to the CDM paradigm. New and independent methods are, therefore, required to assess the level of mass substructure in galaxies in the Local Universe and beyond. Unfortunately, most of these small mass substructures are expected to be completely dark and therefore not directly observable. Strong gravitational lensing provides a unique opportunity to detect and quantify the smallest and faintest substructures at cosmological distances. Thanks to the combination of state-of-the art lens modelling tools and high angular resolution data, we are now able to probe the substructure mass function at a new low mass limit, where competing dark matter models differ by more than two orders of magnitudes. In this talk I will present the latest results and future perspective of substructure lensing.
2016-05-31
17:15
17:15
Cosmic Reionization: Theoretical Modeling and Challenging Observations
Benedetta Ciardi (MPA, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
With the advent of radio telescopes such as LOFAR, MWA, PAPER, a new observational window on the high-redshift universe has been opened. More specifically, we expect in the near future to be able to detect for the first time the 21cm signal from the diffuse Intergalactic Medium (IGM) prior to its full reionization and thus probe the "dark ages". In this talk I will discuss about the theoretical modeling of the reionization process, the observability of the associated 21cm signal and the efforts ongoing within the LOFAR Epoch of Reionization Working Group.
Benedetta Ciardi (MPA, Garching (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
With the advent of radio telescopes such as LOFAR, MWA, PAPER, a new observational window on the high-redshift universe has been opened. More specifically, we expect in the near future to be able to detect for the first time the 21cm signal from the diffuse Intergalactic Medium (IGM) prior to its full reionization and thus probe the "dark ages". In this talk I will discuss about the theoretical modeling of the reionization process, the observability of the associated 21cm signal and the efforts ongoing within the LOFAR Epoch of Reionization Working Group.
2016-05-24
17:15
17:15
Stellar rotation across the cosmic history: from first stars to present day star-planet interactions
Georges Meynet (Genf Obs. Switzerland)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Georges Meynet (Genf Obs. Switzerland)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
2016-05-17
17:15
17:15
Simulating Cosmic Dawn: Predictions for JWST
John Wise (Georgia Institute of Technology, (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Cosmic structure forms hierarchically through smooth accretion and dark matter halo mergers. As a consequence, all galaxies are the product of the dozens of mergers over billions of years. However, one can ask, "What were the first stars and galaxies in the universe?" I will review the current state-of-the-art simulations of early galaxy formation, starting with the formation of the first stars, which are initially devoid of metals and are suggested to have a characteristic mass of tens of solar masses. I will then present results from a suite of cosmological radiation hydrodynamics simulations that focus on the transition from the first stars to the first galaxies. Each simulation captures the radiative and chemical feedback from 10,000 first stars, leading to the formation of a 10^8 solar mass galaxy only 500 million years after the Big Bang, which is detectable with the upcoming James Webb Space Telescope. We have found that the galaxy luminosity function flattens at UV magnitudes above -14 due to feedback effects, and I will present theoretical predictions for their photometry and effects from dust extinction. I will also demonstrate that these faintest galaxies are the primary driver of the reionization of the universe, only to be suppressed by photo-heating at later times, perhaps evolving into a subset of dwarf galaxies in the local universe.
John Wise (Georgia Institute of Technology, (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
Cosmic structure forms hierarchically through smooth accretion and dark matter halo mergers. As a consequence, all galaxies are the product of the dozens of mergers over billions of years. However, one can ask, "What were the first stars and galaxies in the universe?" I will review the current state-of-the-art simulations of early galaxy formation, starting with the formation of the first stars, which are initially devoid of metals and are suggested to have a characteristic mass of tens of solar masses. I will then present results from a suite of cosmological radiation hydrodynamics simulations that focus on the transition from the first stars to the first galaxies. Each simulation captures the radiative and chemical feedback from 10,000 first stars, leading to the formation of a 10^8 solar mass galaxy only 500 million years after the Big Bang, which is detectable with the upcoming James Webb Space Telescope. We have found that the galaxy luminosity function flattens at UV magnitudes above -14 due to feedback effects, and I will present theoretical predictions for their photometry and effects from dust extinction. I will also demonstrate that these faintest galaxies are the primary driver of the reionization of the universe, only to be suppressed by photo-heating at later times, perhaps evolving into a subset of dwarf galaxies in the local universe.
2016-05-10
17:15
17:15
Spectroscopic Studies of Galaxies in the Reionisation Era
Richard Ellis (ESO & Caltech)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Deep exposures with the Hubble Space Telescope (HST) have provided the primary evidence that star-forming galaxies were present in the first billion years of cosmic history. Sometime during this early period the intergalactic medium transitioned from a neutral gas to one that is fully ionized. How did this `cosmic reionization' occur and were star-forming galaxies responsible? Imaging of deep fields with HST's Wide Field Camera 3 in conjunction with Spitzer photometry and Keck spectroscopy has provided important new insight into understanding when reionization occurred and the role of early galaxies in the process. Recent Planck results on the optical depth of electron scattering to CMB photons provide complementary information. I will review this rapid progress in our understanding of the last missing piece in our overall picture of cosmic history and discuss the remaining challenges ahead of future facilities such as JWST and E-ELT.
Richard Ellis (ESO & Caltech)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Deep exposures with the Hubble Space Telescope (HST) have provided the primary evidence that star-forming galaxies were present in the first billion years of cosmic history. Sometime during this early period the intergalactic medium transitioned from a neutral gas to one that is fully ionized. How did this `cosmic reionization' occur and were star-forming galaxies responsible? Imaging of deep fields with HST's Wide Field Camera 3 in conjunction with Spitzer photometry and Keck spectroscopy has provided important new insight into understanding when reionization occurred and the role of early galaxies in the process. Recent Planck results on the optical depth of electron scattering to CMB photons provide complementary information. I will review this rapid progress in our understanding of the last missing piece in our overall picture of cosmic history and discuss the remaining challenges ahead of future facilities such as JWST and E-ELT.
2016-05-03
17:15
17:15
Rare Elements from the First Stars to Today
Ian Roederer (Univ. of Michigan, Dept. of Astronomy, Ann Arbor (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the origin of the elements is one of the major challenges of modern astrophysics. Elements along the bottom two-thirds of the periodic table---including arsenic, selenium, barium, europium, lead, thorium, uranium, and others---are mainly produced by neutron-capture reactions. Some had not been detected previously in late-type stars, and the origins of all are not fully understood at present. My work focuses on abundances derived from ultraviolet and optical high-resolution spectroscopic data of dwarf galaxies, globular clusters, and field stars in the stellar halo. I will present recent observations of these elements that successfully muddy our understanding of when and how they were first produced in the early Universe.
Ian Roederer (Univ. of Michigan, Dept. of Astronomy, Ann Arbor (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the origin of the elements is one of the major challenges of modern astrophysics. Elements along the bottom two-thirds of the periodic table---including arsenic, selenium, barium, europium, lead, thorium, uranium, and others---are mainly produced by neutron-capture reactions. Some had not been detected previously in late-type stars, and the origins of all are not fully understood at present. My work focuses on abundances derived from ultraviolet and optical high-resolution spectroscopic data of dwarf galaxies, globular clusters, and field stars in the stellar halo. I will present recent observations of these elements that successfully muddy our understanding of when and how they were first produced in the early Universe.
2016-04-26
17:15
17:15
The Rosetta/Philae mission to comet 67P/Churyumov-Gerasimenko
Harald Krüger (MPI for solar system research, Göttingen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Comets are among the oldest remnants left over from the beginning of our solar system about 4.6 billion years ago. They are considered key in understanding this very early phase. In August 2014 the European spacecraft Rosetta encountered its target comet 67P/Churyumov-Gerasimenko and became the first artificial satellite of a cometary nucleus. Rosetta carried the lander spacecraft Philae on board which landed on the surface of the comet nucleus on 12 November 2014. Both, the lander Philae and the Rosetta orbiter have studied the comet in unprecedented detail. In the talk I will give an overview about the Rosetta mission, its scientific goals and the results achieved so far.
Harald Krüger (MPI for solar system research, Göttingen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Comets are among the oldest remnants left over from the beginning of our solar system about 4.6 billion years ago. They are considered key in understanding this very early phase. In August 2014 the European spacecraft Rosetta encountered its target comet 67P/Churyumov-Gerasimenko and became the first artificial satellite of a cometary nucleus. Rosetta carried the lander spacecraft Philae on board which landed on the surface of the comet nucleus on 12 November 2014. Both, the lander Philae and the Rosetta orbiter have studied the comet in unprecedented detail. In the talk I will give an overview about the Rosetta mission, its scientific goals and the results achieved so far.
2016-02-02
17:15
17:15
A PHAT New Measurement of the High-Mass IMF
Daniel R. Weisz (UC Berkeley)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The initial mass function (IMF) for stars above ~1 Msun is essential to testing and validating theories of star formation, constraining chemical enrichment models, the frequency of core-collapse supernovae, and interpreting the stellar populations of galaxies across cosmic time. Yet, despite more than 60 years of research, observational constraints on the high-mass IMF remain remarkably uncertain. Widely used high-mass IMFs (e.g., Kroupa) have associated uncertainties approaching an order-of-magnitude, making it virtually impossible to determine if the high-mass IMF varies with respect to environment (e.g., metallicity or star formation intensity) or is “Universal". In this talk, I will present the most precise measurement of the high-mass IMF to date. Using ~100 young, resolved star clusters in M31 imaged as part of the Panchromatic Hubble Andromeda Treasury (PHAT) survey, we find the high-mass IMF slope to be Gamma=1.45+/-0.03. Compared to the canonical Kroupa IMF (Gamma=1.3+/-0.7), the high-mass IMF in M31 is 0.15 dex steeper (i.e., fewer massive stars) and represents a factor of ~20 improvement in precision. There are no significant trends between the cluster IMF slopes and their ages, masses, and sizes, indicating that the IMF is remarkably “Universal” in this sample of ~100 clusters. I will illustrate some of the broader implications of a steeper IMF slope (e.g., on star formation rate indicators, core-collapse supernovae rates) and will conclude by discussing the prospects for precision IMF measurements in other environments.
Daniel R. Weisz (UC Berkeley)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The initial mass function (IMF) for stars above ~1 Msun is essential to testing and validating theories of star formation, constraining chemical enrichment models, the frequency of core-collapse supernovae, and interpreting the stellar populations of galaxies across cosmic time. Yet, despite more than 60 years of research, observational constraints on the high-mass IMF remain remarkably uncertain. Widely used high-mass IMFs (e.g., Kroupa) have associated uncertainties approaching an order-of-magnitude, making it virtually impossible to determine if the high-mass IMF varies with respect to environment (e.g., metallicity or star formation intensity) or is “Universal". In this talk, I will present the most precise measurement of the high-mass IMF to date. Using ~100 young, resolved star clusters in M31 imaged as part of the Panchromatic Hubble Andromeda Treasury (PHAT) survey, we find the high-mass IMF slope to be Gamma=1.45+/-0.03. Compared to the canonical Kroupa IMF (Gamma=1.3+/-0.7), the high-mass IMF in M31 is 0.15 dex steeper (i.e., fewer massive stars) and represents a factor of ~20 improvement in precision. There are no significant trends between the cluster IMF slopes and their ages, masses, and sizes, indicating that the IMF is remarkably “Universal” in this sample of ~100 clusters. I will illustrate some of the broader implications of a steeper IMF slope (e.g., on star formation rate indicators, core-collapse supernovae rates) and will conclude by discussing the prospects for precision IMF measurements in other environments.
2016-01-26
17:15
17:15
Cosmic Rays: from sources to Earth
Pasquale Blasi (Arceri Astrophys. Obs. Firenze (Italy))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The quest for the origin of cosmic rays is more than a century old now. I will discuss some of the reasons why it is taking that long to figure out the answer to this problem. The simple picture of supernovae as sources and diffusion as a paradigm for transport seems to work well. Yet, the validity of many of the underlying assumptions of such an easy picture are questionable and the phenomenology arising from recent observations is getting too rich to be accommodated in these simple models. I will make an attempt at looking at the problem from the point of view of the basic physical elements that both acceleration and transport of cosmic rays rely upon and use this background to show that there is a rich phenomenology that arises from introducing basic principles, whenever possible, into the game. Sometimes this approach helps confirming and sometimes challenges the simple models of acceleration and transport that have been proposed through the years. Present and future observations will be discussed as tools to understand which way to go at the crossroads ahead.
Pasquale Blasi (Arceri Astrophys. Obs. Firenze (Italy))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The quest for the origin of cosmic rays is more than a century old now. I will discuss some of the reasons why it is taking that long to figure out the answer to this problem. The simple picture of supernovae as sources and diffusion as a paradigm for transport seems to work well. Yet, the validity of many of the underlying assumptions of such an easy picture are questionable and the phenomenology arising from recent observations is getting too rich to be accommodated in these simple models. I will make an attempt at looking at the problem from the point of view of the basic physical elements that both acceleration and transport of cosmic rays rely upon and use this background to show that there is a rich phenomenology that arises from introducing basic principles, whenever possible, into the game. Sometimes this approach helps confirming and sometimes challenges the simple models of acceleration and transport that have been proposed through the years. Present and future observations will be discussed as tools to understand which way to go at the crossroads ahead.
2016-01-19
17:15
17:15
Regulation of Star Formation in Galactic Disks
Eva Schinnerer (MPIA, Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the processes that regulate the formation of stars within galaxies is one of the major themes in current astrophysical research. Giant Molecular Clouds (GMCs, size ~ 50pc) are thought to play a critical role in these processes as they host most of the massive star formation occurring in our Galaxy. Detailed observations on scales of clouds can provide important insights on the properties of the star forming interstellar medium and conditions promoting the formation of massive stars. Using such detailed studies of the nearby grand-design spiral galaxy M51 as part of the Pbdi Arcsecond Whirlpool Survey (PAWS) as an example, I will present our current understanding of how the interstellar medium, its molecular component in particular, and star formation relate across galactic disks.
Eva Schinnerer (MPIA, Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Understanding the processes that regulate the formation of stars within galaxies is one of the major themes in current astrophysical research. Giant Molecular Clouds (GMCs, size ~ 50pc) are thought to play a critical role in these processes as they host most of the massive star formation occurring in our Galaxy. Detailed observations on scales of clouds can provide important insights on the properties of the star forming interstellar medium and conditions promoting the formation of massive stars. Using such detailed studies of the nearby grand-design spiral galaxy M51 as part of the Pbdi Arcsecond Whirlpool Survey (PAWS) as an example, I will present our current understanding of how the interstellar medium, its molecular component in particular, and star formation relate across galactic disks.
2016-01-12
17:15
17:15
The gamma-ray Universe
Stefan Funk (Phys. Inst., Erlangen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The field of gamma-ray astrophysics has received considerable attention in recent years. This is in part due to the success of the combination of satellite-based instruments such as Fermi-LAT coupled with Imaging Atmospheric Cherenkov Telescopes (IACTs) like H.E.S.S. measuring gamma-rays over a remarkably large energy range from several 10s of MeV to beyond 100 TeV. These observations demonstrated that the Universe is populated by numerous exotic and violent phenomena. The astrophysical objects from which we detect gamma rays generate enormous amounts of energy and accelerate particles to energies way beyond those accessible in human-made accelerators. The gamma-ray observations have also demonstrated, that they provide serious constraints on the annihilation cross section of dark matter in situ. In this talk I will describe the status and the future potential of gamma-ray observations of the Universe.
Stefan Funk (Phys. Inst., Erlangen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The field of gamma-ray astrophysics has received considerable attention in recent years. This is in part due to the success of the combination of satellite-based instruments such as Fermi-LAT coupled with Imaging Atmospheric Cherenkov Telescopes (IACTs) like H.E.S.S. measuring gamma-rays over a remarkably large energy range from several 10s of MeV to beyond 100 TeV. These observations demonstrated that the Universe is populated by numerous exotic and violent phenomena. The astrophysical objects from which we detect gamma rays generate enormous amounts of energy and accelerate particles to energies way beyond those accessible in human-made accelerators. The gamma-ray observations have also demonstrated, that they provide serious constraints on the annihilation cross section of dark matter in situ. In this talk I will describe the status and the future potential of gamma-ray observations of the Universe.
2015-12-22
17:15
17:15
The end of the Cretaceous: the causes for the dinosaur extinction 65 Myr ago
Christina Ifrim (Inst. Geowiss., Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Cretaceous period ended ca. 65 Myr ago with one of the largest mass extinctions known in Earth history. Dinosaurs, ammonites and many other groups of organisms were eliminated forever from our planet. The causes for this severe overturn on Earth have been under vivid debate for 35 years now. The discussion was initiated with the widely known hypothesis that the crisis was the consequence of a bolide impact. But what is the geological evidence for such a hypothesis? Can a global extinction event be triggered by impact alone? And is that all that happened at the end of the Cretaceous? This talk gives you insight into the origin of the impact scenario, but also to alternative explanations, and an update of the research on this extinction, which is far from being explained.
Christina Ifrim (Inst. Geowiss., Heidelberg (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Cretaceous period ended ca. 65 Myr ago with one of the largest mass extinctions known in Earth history. Dinosaurs, ammonites and many other groups of organisms were eliminated forever from our planet. The causes for this severe overturn on Earth have been under vivid debate for 35 years now. The discussion was initiated with the widely known hypothesis that the crisis was the consequence of a bolide impact. But what is the geological evidence for such a hypothesis? Can a global extinction event be triggered by impact alone? And is that all that happened at the end of the Cretaceous? This talk gives you insight into the origin of the impact scenario, but also to alternative explanations, and an update of the research on this extinction, which is far from being explained.
2015-12-15
17:15
17:15
Star and Planet Formation with the Atacama Large Millimetre/submillimetre Array
Leonardo Testi (ESO,Garching)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
ALMA is the leading facility for the observations of the cool Universe (and not only). After two decades of design and construction, this unique and transformational observatory has started Early Science operations four years ago and is now about to enter the Full Science phase. In this talk I will give an overview of ALMA , its capabilities and long term upgrade plan, which will maintain it a world leading ground based observational facility for at least two deacades. While giving an overview of the observatory and its capabilities, I will mostly focus on its contributions to our understanding of the star and planet formation processes.
Leonardo Testi (ESO,Garching)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
ALMA is the leading facility for the observations of the cool Universe (and not only). After two decades of design and construction, this unique and transformational observatory has started Early Science operations four years ago and is now about to enter the Full Science phase. In this talk I will give an overview of ALMA , its capabilities and long term upgrade plan, which will maintain it a world leading ground based observational facility for at least two deacades. While giving an overview of the observatory and its capabilities, I will mostly focus on its contributions to our understanding of the star and planet formation processes.
2015-12-08
17:15
17:15
Supermassive Black Holes: From Jets to the Event Horizon
Silke Britzen (MPI Radioastronomie, Bonn (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Highest resolution Event Horizon Telescope (EHT) observations will probably soon tell us more about the supermassive black hole at the Galactic Centre (Sgr A*) and the cores of nearby Active Galactic Nuclei (AGN). It might also help to clarify the long-standing question whether the central massive objects in AGN are instead close pairs of black holes. Mergers of supermassive black hole pairs are expected to generate the strongest gravitational wave signals. I will present examples of how we identify potential close binary black hole candidates based on the combined analysis of high resolution radio interferometric (VLBI) observations and multi- wavelength data. I will also provide an outlook on the scientific prospects with regard to future EHT-observations.
Silke Britzen (MPI Radioastronomie, Bonn (Germany))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Highest resolution Event Horizon Telescope (EHT) observations will probably soon tell us more about the supermassive black hole at the Galactic Centre (Sgr A*) and the cores of nearby Active Galactic Nuclei (AGN). It might also help to clarify the long-standing question whether the central massive objects in AGN are instead close pairs of black holes. Mergers of supermassive black hole pairs are expected to generate the strongest gravitational wave signals. I will present examples of how we identify potential close binary black hole candidates based on the combined analysis of high resolution radio interferometric (VLBI) observations and multi- wavelength data. I will also provide an outlook on the scientific prospects with regard to future EHT-observations.
2015-12-01
17:15
17:15
Convection and rotations in stars
Steven Balbus (Dept. Phys., Univ. Oxford (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The internal rotational profile of the Sun is now known with great accuracy. The results initially were a great surprise. A dominant pattern of rotation on cylinders was expected, but instead, the dominant feature in the bulk of the convective zone was found to be rotation on cones of (nearly) constant latitude. At the base of the convection zone, strong radial shear---the so-called tachocline---is present. In this talk, I will show how these apparently surprising properties follow from a few simple ideas, and discuss predictions for asteroseismology measurements.
Steven Balbus (Dept. Phys., Univ. Oxford (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The internal rotational profile of the Sun is now known with great accuracy. The results initially were a great surprise. A dominant pattern of rotation on cylinders was expected, but instead, the dominant feature in the bulk of the convective zone was found to be rotation on cones of (nearly) constant latitude. At the base of the convection zone, strong radial shear---the so-called tachocline---is present. In this talk, I will show how these apparently surprising properties follow from a few simple ideas, and discuss predictions for asteroseismology measurements.
2015-11-24
17:15
17:15
How much iron is in our stars ?
Karin Lind (Dept. Phys. & Astron., Uppsala Univ. (Sweden))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The spectra of cool stars are filled with lines of atomic iron, to the extent that the stellar [Fe/H] if often used as a proxy for the entire metal content of stars. Further, the excitation and ionisation balance of neutral and singly ionised iron is often used for determination of reddening-free stellar parameters. Together this makes [Fe/H] arguably the most important parameter for Galactic archaeology. Recent years have seen parallel developments of atomic data, stellar atmospheric modelling, and spectrum synthesis tools, culminating in a very important milestone; iron abundance analysis no longer requires calibration of free parameters. I will discuss the consequences that accurate iron abundances have for studies of chemical evolution.
Karin Lind (Dept. Phys. & Astron., Uppsala Univ. (Sweden))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
The spectra of cool stars are filled with lines of atomic iron, to the extent that the stellar [Fe/H] if often used as a proxy for the entire metal content of stars. Further, the excitation and ionisation balance of neutral and singly ionised iron is often used for determination of reddening-free stellar parameters. Together this makes [Fe/H] arguably the most important parameter for Galactic archaeology. Recent years have seen parallel developments of atomic data, stellar atmospheric modelling, and spectrum synthesis tools, culminating in a very important milestone; iron abundance analysis no longer requires calibration of free parameters. I will discuss the consequences that accurate iron abundances have for studies of chemical evolution.
2015-11-17
17:15
17:15
Learning about the Dark Matter with stellar streams
Vasily Belokurov (Inst. Astron., Univ. Cambridge (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Stellar streams can be used to measure the properties of the gravitational potential of the Milky Way. Impressively, such hard-to-get parameters as the halo concentration, its shape, even the lumpiness of the Galactic Dark Matter distribution can all be accurately constrained. In principle. However, there are curious complications along the way.
Vasily Belokurov (Inst. Astron., Univ. Cambridge (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Stellar streams can be used to measure the properties of the gravitational potential of the Milky Way. Impressively, such hard-to-get parameters as the halo concentration, its shape, even the lumpiness of the Galactic Dark Matter distribution can all be accurately constrained. In principle. However, there are curious complications along the way.
2015-11-10
17:15
17:15
Galaxy Formation at its Peak
Avishai Dekel (Racah Inst. Phys., The Hebrew Univ., Jerusalem (Israel))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The most active phase of galaxy formation, during the first few Gigayears of cosmic history, is optimal for a study of the key processes that drive galaxy evolution. In this phase, massive galaxies at the nodes of the cosmic web are fed by intense streams including a smooth component and merging galaxies. This setting introduces new theoretical challenges, such as: (a) How do galaxies acquire the angular momentum that determines their structure? (b) What is the nature of the violent disk instability in high-z star-forming galaxies? (c) How do galaxies turn into compact star-forming “blue nuggets” with AGN? (d) What are the quenching mechanisms that lead to passive compact spheroidal “red nuggets”? (e) Why are the star-forming galaxies confined to a narrow Main Sequence? These issues will be addressed, based on cosmological simulations and analytic models, and their theoretical and observational implications will be discussed.
Avishai Dekel (Racah Inst. Phys., The Hebrew Univ., Jerusalem (Israel))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The most active phase of galaxy formation, during the first few Gigayears of cosmic history, is optimal for a study of the key processes that drive galaxy evolution. In this phase, massive galaxies at the nodes of the cosmic web are fed by intense streams including a smooth component and merging galaxies. This setting introduces new theoretical challenges, such as: (a) How do galaxies acquire the angular momentum that determines their structure? (b) What is the nature of the violent disk instability in high-z star-forming galaxies? (c) How do galaxies turn into compact star-forming “blue nuggets” with AGN? (d) What are the quenching mechanisms that lead to passive compact spheroidal “red nuggets”? (e) Why are the star-forming galaxies confined to a narrow Main Sequence? These issues will be addressed, based on cosmological simulations and analytic models, and their theoretical and observational implications will be discussed.
2015-11-03
17:15
17:15
Radiative Feedback and the Formation of Massive Stars and Clusters
Ralph E. Pudritz (McMaster Univ. Hamilton (Canada))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The formation of massive stars and their accretion disks remains one of the outstanding problems of star formation. For massive stars and clusters, radiative feedback is a key process that may limit their masses. I will discuss the physical problems and large body of work that has addressed these questions before turning to our own contributions. For massive star formation, we have developed a new hybrid radiative transfer code that operates in a full 3D, adaptive mesh environment that can, for the first time, follow heating of gas by both discrete stellar sources as well as by diffuse radiative background. We used it to simulate the formation of massive stars during the collapse of 30 to 200 solar mass cores. We find that forming massive disks undergo gravitational instabilities at some time during their formation that drive spiral waves and very high accretion rates onto the protostellar cores. It is at this time that radiatively driven bubbles and outflows are launched. There are no signs of any fallback of cooled material from the bubblesor that radiative feedback drastically limits stellar mass independently of the initial mass reservoir. We find that radiatively heated disks also do not undergo the fragmentation reported in earlier work. Our results compare well with the recent observations of massive disk properties around forming O stars. I will also present first results of our new work on radiative feedback simulations of the formation of young clusters in turbulent Giant Molecular Clouds and on how cloud structure affects this process
Ralph E. Pudritz (McMaster Univ. Hamilton (Canada))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The formation of massive stars and their accretion disks remains one of the outstanding problems of star formation. For massive stars and clusters, radiative feedback is a key process that may limit their masses. I will discuss the physical problems and large body of work that has addressed these questions before turning to our own contributions. For massive star formation, we have developed a new hybrid radiative transfer code that operates in a full 3D, adaptive mesh environment that can, for the first time, follow heating of gas by both discrete stellar sources as well as by diffuse radiative background. We used it to simulate the formation of massive stars during the collapse of 30 to 200 solar mass cores. We find that forming massive disks undergo gravitational instabilities at some time during their formation that drive spiral waves and very high accretion rates onto the protostellar cores. It is at this time that radiatively driven bubbles and outflows are launched. There are no signs of any fallback of cooled material from the bubblesor that radiative feedback drastically limits stellar mass independently of the initial mass reservoir. We find that radiatively heated disks also do not undergo the fragmentation reported in earlier work. Our results compare well with the recent observations of massive disk properties around forming O stars. I will also present first results of our new work on radiative feedback simulations of the formation of young clusters in turbulent Giant Molecular Clouds and on how cloud structure affects this process
2015-10-27
17:15
17:15
Cosmological Calorimetry: The nature of the intergalactic medium and the photon underproduction crisis
Juna A. Kollmeier (Carnegie Science, Washington (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Lyman alpha forest remains one of the most robust predictions of cosmological hydrodynamic simulations. Lyman alpha absorption lines have been used for decades to trace cosmic structures that -- only recently, with the exquisite sensitivity achievable with modern instruments -- are beginning to be detected in emission as well. I will discuss the predicted morphology of the Lyman alpha forest and the possibility of revealing this structure with Lyman alpha imaging surveys. The emission signal is dependent on the ionizing background radiation which, at high redshift, is well-understood and constrained. However, I will show that at low redshift there is a huge mismatch between our expectations and observations. I describe a factor of 5 discrepancy between the value of the photoionization rate required to match cosmological models of the z = 0 intergalactic medium to observations of the Lyman alpha forest and the value predicted by state-of-the-art models that account for the emissivity of stars and quasars over time. Examining potential resolutions to this problem, I will demonstrate that solving it requires, at minimum, a major revision of our thinking about the low redshift universe.
Juna A. Kollmeier (Carnegie Science, Washington (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Lyman alpha forest remains one of the most robust predictions of cosmological hydrodynamic simulations. Lyman alpha absorption lines have been used for decades to trace cosmic structures that -- only recently, with the exquisite sensitivity achievable with modern instruments -- are beginning to be detected in emission as well. I will discuss the predicted morphology of the Lyman alpha forest and the possibility of revealing this structure with Lyman alpha imaging surveys. The emission signal is dependent on the ionizing background radiation which, at high redshift, is well-understood and constrained. However, I will show that at low redshift there is a huge mismatch between our expectations and observations. I describe a factor of 5 discrepancy between the value of the photoionization rate required to match cosmological models of the z = 0 intergalactic medium to observations of the Lyman alpha forest and the value predicted by state-of-the-art models that account for the emissivity of stars and quasars over time. Examining potential resolutions to this problem, I will demonstrate that solving it requires, at minimum, a major revision of our thinking about the low redshift universe.
2015-10-20
17:15
17:15
Collapse and Star Formation in Self-gravitating Turbulent Fluids
Norman Murray (Canadian Inst. Theor. Astrophys., Univ. Toronto (Canada))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Observations of star forming regions in the Milky Way have established that stars form in large molecular clouds or GMCs. The spectral lines of these GMCs are usually interpreted as the signature of turbulent motion. The kinetic energy in the turbulence is similar to the gravitational binding energy of the GMC. Work over the last decade, including research done in Heidelberg, suggests that stars form in converging flows in this turbulence. I will describe recent analytic and numerical work that has resulted in a detailed description of the evolution of such converging flows. I will show that the flows set up density structures that do not vary with time; the converging gas flows through fixed run of density onto a central star or star cluster. The collapse drives turbulent motions, resulting in deviations from Larson's Law (the size-linewidth relation), and slowing the inflow velocity below the free-fall rate. However, the infall velocity is proportional to the square root of stellar mass, resulting in a mass accretion rate that grows linearly with time.
Norman Murray (Canadian Inst. Theor. Astrophys., Univ. Toronto (Canada))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Observations of star forming regions in the Milky Way have established that stars form in large molecular clouds or GMCs. The spectral lines of these GMCs are usually interpreted as the signature of turbulent motion. The kinetic energy in the turbulence is similar to the gravitational binding energy of the GMC. Work over the last decade, including research done in Heidelberg, suggests that stars form in converging flows in this turbulence. I will describe recent analytic and numerical work that has resulted in a detailed description of the evolution of such converging flows. I will show that the flows set up density structures that do not vary with time; the converging gas flows through fixed run of density onto a central star or star cluster. The collapse drives turbulent motions, resulting in deviations from Larson's Law (the size-linewidth relation), and slowing the inflow velocity below the free-fall rate. However, the infall velocity is proportional to the square root of stellar mass, resulting in a mass accretion rate that grows linearly with time.
2015-07-21
17:15
17:15
Life and Death of the First Stars
Alexander Heger (Monash Univ. (Australia))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The first stars are unique not only in being first but also because of being first, they have a unique and pristine primordial initial composition, which can dramatically alter both their evolution, the way they die as supernovae, and their resulting nucleosynthesis. For example, the recently discovered most iron-poor star known, SM0313-6708, hints at some primordial production process of calcium that can only be found and seen in such pristine stars. Another example is that reduced mass loss and higher characteristic initial masses may lead to a population of pair instability supernovae that could produce a very unique abundance pattern. No direct observations of these stars are possible at this time, however, so our ability to study these early stars is limited to indirect measurements and numerical simulations, though possibly we might be able to observe some of their stellar deaths in the near future. Stellar forensics based on nucleosynthesis patterns preserved in subsequent generations of stars may be used to attempt reconstruction of the properties of these first stars. But in order to be able to use this tool, we need know what abundances were synthesised in these first generations of stars.
Alexander Heger (Monash Univ. (Australia))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
The first stars are unique not only in being first but also because of being first, they have a unique and pristine primordial initial composition, which can dramatically alter both their evolution, the way they die as supernovae, and their resulting nucleosynthesis. For example, the recently discovered most iron-poor star known, SM0313-6708, hints at some primordial production process of calcium that can only be found and seen in such pristine stars. Another example is that reduced mass loss and higher characteristic initial masses may lead to a population of pair instability supernovae that could produce a very unique abundance pattern. No direct observations of these stars are possible at this time, however, so our ability to study these early stars is limited to indirect measurements and numerical simulations, though possibly we might be able to observe some of their stellar deaths in the near future. Stellar forensics based on nucleosynthesis patterns preserved in subsequent generations of stars may be used to attempt reconstruction of the properties of these first stars. But in order to be able to use this tool, we need know what abundances were synthesised in these first generations of stars.
2015-07-14
17:15
17:15
MASSIVE Galaxies and Small Supermassive Black Holes
Jenny E. Green (Princeton Univ., (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will discuss MASSIVE, an ambitious new integral-field survey of the ~100 most massive galaxies within 100 Mpc. Using integral-field spectroscopy covering 200 pc to 20 kpc scales, we are studying the assembly history of massive galaxies from the supermassive black holes at the center to the dark matter halos on large scales. I will then discuss black hole scaling relations over a large range in galaxy mass, using MASSIVE observations at the high end and megamaser disk galaxies at low mass. If time permits, I will discuss progress on survey planning for the Prime Focus Spectrograph.
Jenny E. Green (Princeton Univ., (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
I will discuss MASSIVE, an ambitious new integral-field survey of the ~100 most massive galaxies within 100 Mpc. Using integral-field spectroscopy covering 200 pc to 20 kpc scales, we are studying the assembly history of massive galaxies from the supermassive black holes at the center to the dark matter halos on large scales. I will then discuss black hole scaling relations over a large range in galaxy mass, using MASSIVE observations at the high end and megamaser disk galaxies at low mass. If time permits, I will discuss progress on survey planning for the Prime Focus Spectrograph.
2015-07-07
17:15
17:15
Evolved planetary systems around white dwarfs
Boris Gänsicke (Dept. of Phys., Univ. Warwick (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We know over 1500 extra-solar planets, and the past few years have seen a rapid expansion of the parameter space to wider ranges in host star and planet mass, as well as larger orbital separations. Consequently, the architectures of the known planetary systems are becoming increasingly diverse, and so does the entire field of exo-planets. The questions that the study of white dwarfs can address are: What is the future of the known exo-planetary systems as their host stars evolve of the main-sequence? And what will happen to the solar system once the Sun dies? How can we detect evolved planetary systems? And what can they teach us? The strong surface gravity of white dwarfs implies that metals will sink out of the photosphere on time-scales that are orders of magnitude shorter than their cooling ages, and therefore white dwarfs are expected to have either pure hydrogen or helium atmospheres. Yet, the existence of metal-polluted white dwarfs has been a conundrum for nearly a century. We know now that these white dwarfs are polluted by accretion of rocky debris, remnants of a former planetary system. With hindsight, this is may not come as too much of a surprise, as our Sun will eventually evolve in a white dwarf orbited by Mars, the outer planets, and hosts of asteroids - and a similar fate awaits many of the known exo-planetary systems! The photospheric abundances of these white dwarfs mirror those of the debris they accrete, hence we can directly, and accurately measure the bulk abundance of extra-solar planetary material. In zeroth approximation, the abundance pattern measured so far are overall similar to those of the terrestrial planets in the Solar system. At a closer look, there is evidence for a variety of thermal processing and possibly differentiation in the parent bodies, and even for the accretion of water. Perhaps most astonishing are the lower limits on the mass of the parent bodies that were accreted, ranging up to 1e24g, i.e. well above the most massive asteroids in the Solar system. These chemical abundance analyses are currently, and for some time to come, by far the most precise studies of extra-solar planetary material. These recent discoveries raise many new questions: what is the architecture of planetary systems on the post-main sequence? What type of planetary bodies are delivered to the white dwarf, and how? What is the long-term evolution of these systems? A suite of recent simulations gives a glimpse into some possible answers.
Boris Gänsicke (Dept. of Phys., Univ. Warwick (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
We know over 1500 extra-solar planets, and the past few years have seen a rapid expansion of the parameter space to wider ranges in host star and planet mass, as well as larger orbital separations. Consequently, the architectures of the known planetary systems are becoming increasingly diverse, and so does the entire field of exo-planets. The questions that the study of white dwarfs can address are: What is the future of the known exo-planetary systems as their host stars evolve of the main-sequence? And what will happen to the solar system once the Sun dies? How can we detect evolved planetary systems? And what can they teach us? The strong surface gravity of white dwarfs implies that metals will sink out of the photosphere on time-scales that are orders of magnitude shorter than their cooling ages, and therefore white dwarfs are expected to have either pure hydrogen or helium atmospheres. Yet, the existence of metal-polluted white dwarfs has been a conundrum for nearly a century. We know now that these white dwarfs are polluted by accretion of rocky debris, remnants of a former planetary system. With hindsight, this is may not come as too much of a surprise, as our Sun will eventually evolve in a white dwarf orbited by Mars, the outer planets, and hosts of asteroids - and a similar fate awaits many of the known exo-planetary systems! The photospheric abundances of these white dwarfs mirror those of the debris they accrete, hence we can directly, and accurately measure the bulk abundance of extra-solar planetary material. In zeroth approximation, the abundance pattern measured so far are overall similar to those of the terrestrial planets in the Solar system. At a closer look, there is evidence for a variety of thermal processing and possibly differentiation in the parent bodies, and even for the accretion of water. Perhaps most astonishing are the lower limits on the mass of the parent bodies that were accreted, ranging up to 1e24g, i.e. well above the most massive asteroids in the Solar system. These chemical abundance analyses are currently, and for some time to come, by far the most precise studies of extra-solar planetary material. These recent discoveries raise many new questions: what is the architecture of planetary systems on the post-main sequence? What type of planetary bodies are delivered to the white dwarf, and how? What is the long-term evolution of these systems? A suite of recent simulations gives a glimpse into some possible answers.
2015-06-30
17:15
17:15
The Fourth Paradigm of Science in Astronomy
Alberto Krone-Martins (Univ. of Lisboa (Portugal))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Alberto Krone-Martins (Univ. of Lisboa (Portugal))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
2015-06-23
17:15
17:15
Active asteroids: primordial ice, collisions, rotational breakup?
Jessica Agarwal (MPI für Sonnensystemforschung, Göttingen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The classical picture of small bodies in the solar system sees comets as volatile-rich, quickly evolving bodies, and asteroids as rather inert pieces of rock and regolith. In recent years, a growing number of known active asteroids have shattered the classical picture. These are small bodies on orbits typical of asteroids, but displaying dust comae and tails similar to comets. Currently, 1-2 new objects are discovered per year, each of which bears new surprises. The population of active asteroids is characterised by great diversity, suggesting that asteroidal dust activity can have a number of different causes, like sublimation of hidden volatiles, collision, or rotational break-up. The talk will give an overview of the currently known population of active asteroids, introduce possible activation mechanisms, and discuss implications for our understanding of asteroids and dust in the solar system.
Jessica Agarwal (MPI für Sonnensystemforschung, Göttingen)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The classical picture of small bodies in the solar system sees comets as volatile-rich, quickly evolving bodies, and asteroids as rather inert pieces of rock and regolith. In recent years, a growing number of known active asteroids have shattered the classical picture. These are small bodies on orbits typical of asteroids, but displaying dust comae and tails similar to comets. Currently, 1-2 new objects are discovered per year, each of which bears new surprises. The population of active asteroids is characterised by great diversity, suggesting that asteroidal dust activity can have a number of different causes, like sublimation of hidden volatiles, collision, or rotational break-up. The talk will give an overview of the currently known population of active asteroids, introduce possible activation mechanisms, and discuss implications for our understanding of asteroids and dust in the solar system.
2015-06-16
17:15
17:15
Black Holes on the Computer
Thomas Baumgarte (Bowdoin College, Main, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Black holes are among the most fascinating predictions of Einstein's 100-year-old theory of general relativity. They are also among the most promising sources of gravitational radiation, which we hope to detect very soon. With a remarkable breakthrough in numerical relativity it has become possible to simulate the merger of binary black holes, and to predict the emitted gravitational wave signals. I will review some of the problems that these calculations presented, as well as their solutions, will report on some of the surprising astrophysical implications of these new simulations, and will outline some current and future challenges.
Thomas Baumgarte (Bowdoin College, Main, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Black holes are among the most fascinating predictions of Einstein's 100-year-old theory of general relativity. They are also among the most promising sources of gravitational radiation, which we hope to detect very soon. With a remarkable breakthrough in numerical relativity it has become possible to simulate the merger of binary black holes, and to predict the emitted gravitational wave signals. I will review some of the problems that these calculations presented, as well as their solutions, will report on some of the surprising astrophysical implications of these new simulations, and will outline some current and future challenges.
2015-06-09
17:15
17:15
Acceleration of particles in astrophysical shocks
Anatoly Spitkovsky (Dept. Phys.& Astron., Princeton Univ. (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Collisionless shocks are ubiquitous throughout the Universe, and are thought to be responsible for the generation of nonthermal particles that span many decades in energy. These particles are observed through synchrotron radiation from astrophysical sources, or directly as energetic cosmic rays. The main acceleration mechanism is known as diffusive shock acceleration, and involves particle scattering and diffusion around a shock wave. Despite its fundamental importance in astrophysics, the details of this mechanism and the conditions for its operation are only now coming to light, thanks to the advent of ab-initio numerical simualtions of collisionless shocks. I will review the progress in kinetic simualtions of shocks, and concentrate on results of the numerical survey of shock parameters, which allows us to understand the efficiency of shock acceleration, associated magnetic field amplification, and the physics of injection of ions and electrons into the acceleration process. These results can be applied to a number of astrophysical scenarios, including nonthermal emission from supernova remnants, jets in active galaxies, and gamma-ray bursts.
Anatoly Spitkovsky (Dept. Phys.& Astron., Princeton Univ. (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Collisionless shocks are ubiquitous throughout the Universe, and are thought to be responsible for the generation of nonthermal particles that span many decades in energy. These particles are observed through synchrotron radiation from astrophysical sources, or directly as energetic cosmic rays. The main acceleration mechanism is known as diffusive shock acceleration, and involves particle scattering and diffusion around a shock wave. Despite its fundamental importance in astrophysics, the details of this mechanism and the conditions for its operation are only now coming to light, thanks to the advent of ab-initio numerical simualtions of collisionless shocks. I will review the progress in kinetic simualtions of shocks, and concentrate on results of the numerical survey of shock parameters, which allows us to understand the efficiency of shock acceleration, associated magnetic field amplification, and the physics of injection of ions and electrons into the acceleration process. These results can be applied to a number of astrophysical scenarios, including nonthermal emission from supernova remnants, jets in active galaxies, and gamma-ray bursts.
2015-06-02
17:15
17:15
Are supernova remnants the dominant sources of Galactic cosmic rays?
Jacco Vink (Univ. Amsterdam (NL))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Supernova remnants have long been recognised as the most likely sources of Galactic cosmic rays. Indeed, studies carried out over the last 10-20 years have shown that supernova remnants do indeed accelerated particles to very high energies of 10-100 TeV. However, for supernova remnants to be the sources of Galactic cosmic rays they should be able to transfer 10% of their kinetic energy to cosmic rays, and accelerate them to at least 3x10^15 eV. In particular this last requirement is at odds with both observational constraints and with our theoretical understanding. I will review where we stand in our knowledge of particle acceleration in supernova remnants, based on multiwavelength data, and I will discuss a promising alternative for the origin of cosmic rays: super bubbles.
Jacco Vink (Univ. Amsterdam (NL))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Supernova remnants have long been recognised as the most likely sources of Galactic cosmic rays. Indeed, studies carried out over the last 10-20 years have shown that supernova remnants do indeed accelerated particles to very high energies of 10-100 TeV. However, for supernova remnants to be the sources of Galactic cosmic rays they should be able to transfer 10% of their kinetic energy to cosmic rays, and accelerate them to at least 3x10^15 eV. In particular this last requirement is at odds with both observational constraints and with our theoretical understanding. I will review where we stand in our knowledge of particle acceleration in supernova remnants, based on multiwavelength data, and I will discuss a promising alternative for the origin of cosmic rays: super bubbles.
2015-05-26
17:15
17:15
(1) Are planetary systems flat? (2) Is statistical mechanics useful for describing the distribution of planetary orbits?
Scott Tremaine (School of Natural Sci., Princeton (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
(1) Laplace argued, correctly, that the small inclinations of planetary orbits implied that the solar system formed from a flat disk. The observational and theoretical evidence on whether extrasolar planetary systems are flat, however, is still ambiguous. I will discuss constraints on flatness from the Kepler spacecraft and other sources; Lidov-Kozai oscillations; and competing migration mechanisms for the formation of giant planets at small orbital radii. (2) I will describe a simple statistical model for the orbit distribution of terrestrial planets, based on the ansatz that the planets explore uniformly all of the stable region of phase space. The predicted properties are generally consistent with both N-body simulations and the Kepler catalog of extrasolar planets.
Scott Tremaine (School of Natural Sci., Princeton (USA))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
(1) Laplace argued, correctly, that the small inclinations of planetary orbits implied that the solar system formed from a flat disk. The observational and theoretical evidence on whether extrasolar planetary systems are flat, however, is still ambiguous. I will discuss constraints on flatness from the Kepler spacecraft and other sources; Lidov-Kozai oscillations; and competing migration mechanisms for the formation of giant planets at small orbital radii. (2) I will describe a simple statistical model for the orbit distribution of terrestrial planets, based on the ansatz that the planets explore uniformly all of the stable region of phase space. The predicted properties are generally consistent with both N-body simulations and the Kepler catalog of extrasolar planets.
2015-05-19
17:15
17:15
Dust-obscured starbursts and their implications for galaxy assembly at early times
Caitlin Casey (UC Irvine, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Dusty star-forming galaxies (DSFGs) host the most intense stellar nurseries in the Universe. Although rare today, they were a factor of 1000 times more common at z~2 and likely contributed significantly to the buildup of the Universe’s stellar mass and the formation of high-mass galaxies. However, an ongoing debate lingers as to their evolutionary origins at high-z. While DSFGs locally are known to be merger-driven collisions of gas-rich disk galaxies, some works argue that high-z DSFGs have different origins, and could just be solitary massive gas-rich disks (continually fed star-forming fuel via the gas-rich IGM). Other conflicting evidence argues high-z DSFGs are major mergers, like their local cousins. Solving the debate, as to the origins of high-z DSFGs, requires a careful census and follow-up of DSFGs. I will describe some of the latest observational research on dusty, infrared-luminous galaxies at high-redshift. Specifically, I will focus on: 1. measuring the far-IR/submm contribution to the cosmic star formation rate density out to high-z, and compare it to the optical/UV contribution to infer the universal importance of infrared surveys out to early epochs, 2. observational tools we can use to surmise the physical mechanisms which drive intense star-formation, and 3. how these rare but extreme galaxies can be uniquely useful as probes of some of the most massive structures in the Universe’s cosmic web. My long-term goal is to understand the triggering mechanisms for star formation episodes in extreme, ultraluminous starburst environments, how they relate to star formation in more common ``Milky Way'' type galaxies at high-redshift, and what the implications are for galaxy evolution at very early times.
Caitlin Casey (UC Irvine, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Dusty star-forming galaxies (DSFGs) host the most intense stellar nurseries in the Universe. Although rare today, they were a factor of 1000 times more common at z~2 and likely contributed significantly to the buildup of the Universe’s stellar mass and the formation of high-mass galaxies. However, an ongoing debate lingers as to their evolutionary origins at high-z. While DSFGs locally are known to be merger-driven collisions of gas-rich disk galaxies, some works argue that high-z DSFGs have different origins, and could just be solitary massive gas-rich disks (continually fed star-forming fuel via the gas-rich IGM). Other conflicting evidence argues high-z DSFGs are major mergers, like their local cousins. Solving the debate, as to the origins of high-z DSFGs, requires a careful census and follow-up of DSFGs. I will describe some of the latest observational research on dusty, infrared-luminous galaxies at high-redshift. Specifically, I will focus on: 1. measuring the far-IR/submm contribution to the cosmic star formation rate density out to high-z, and compare it to the optical/UV contribution to infer the universal importance of infrared surveys out to early epochs, 2. observational tools we can use to surmise the physical mechanisms which drive intense star-formation, and 3. how these rare but extreme galaxies can be uniquely useful as probes of some of the most massive structures in the Universe’s cosmic web. My long-term goal is to understand the triggering mechanisms for star formation episodes in extreme, ultraluminous starburst environments, how they relate to star formation in more common ``Milky Way'' type galaxies at high-redshift, and what the implications are for galaxy evolution at very early times.
2015-05-12
17:15
17:15
New Data, new Methods: Chemodynamic Milky Way Models challenged by modern Surveys
Ralph Schoenrich (Dept. of Phys., Oxford (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Galactic Astronomy is undergoing an unprecedented revolution. The Gaia satellite mission is measuring parallaxes for ~1 billion stars, outperforming its predecessor Hipparcos by 4 orders of magnitude in sample size and 2 orders of magnitude in precision and sample range. It is supported by ground based spectroscopic surveys collecting millions of high quality spectra. The first such data have already changed our understanding and interpretation of galactic structure, e.g. of the Galactic halo, and of galactic dynamics, like radial migration and the origin of the thick disc. I will outline the challenges in understanding these large surveys, give an outlook of the next years and discuss what new observations of the past year tell us about structure and history of the Milky Way.
Ralph Schoenrich (Dept. of Phys., Oxford (UK))
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Galactic Astronomy is undergoing an unprecedented revolution. The Gaia satellite mission is measuring parallaxes for ~1 billion stars, outperforming its predecessor Hipparcos by 4 orders of magnitude in sample size and 2 orders of magnitude in precision and sample range. It is supported by ground based spectroscopic surveys collecting millions of high quality spectra. The first such data have already changed our understanding and interpretation of galactic structure, e.g. of the Galactic halo, and of galactic dynamics, like radial migration and the origin of the thick disc. I will outline the challenges in understanding these large surveys, give an outlook of the next years and discuss what new observations of the past year tell us about structure and history of the Milky Way.
2015-05-05
17:15
17:15
A microscopic approach to cosmic structure formation
Matthias Bartelmann (ITA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
So far, the non-linear evolution of cosmic structures is accessible only for large-scale numerical simulations. The conventional analytic treatment of cosmic density fluctuations with the hydrodynamical equations runs into severe conceptual and technical difficulties even on moderately non-linear scales. As an alternative, we have developed a microscopic, non-equilibrium, statistical theory for cosmic structure formation which avoids these difficulties by construction and allows to enter deeply into the non-linear regime of cosmic density fluctuations. The theory also allows to unify approaches to kinetic theory and hydrodynamics, offering a joint treatment of dark and baryonic matter. I will motivate and introduce this theory in simple terms, show some results on non-linear cosmic structure formation obtained so far, and discuss some possible future applications.
Matthias Bartelmann (ITA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
So far, the non-linear evolution of cosmic structures is accessible only for large-scale numerical simulations. The conventional analytic treatment of cosmic density fluctuations with the hydrodynamical equations runs into severe conceptual and technical difficulties even on moderately non-linear scales. As an alternative, we have developed a microscopic, non-equilibrium, statistical theory for cosmic structure formation which avoids these difficulties by construction and allows to enter deeply into the non-linear regime of cosmic density fluctuations. The theory also allows to unify approaches to kinetic theory and hydrodynamics, offering a joint treatment of dark and baryonic matter. I will motivate and introduce this theory in simple terms, show some results on non-linear cosmic structure formation obtained so far, and discuss some possible future applications.
2015-04-28
17:15
17:15
Extragalactic Archeology
Charlie Conroy (Harvard Smithsonian Center Astrophys., Cambridge)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
One of the primary avenues for understanding the formation and evolution of galaxies is through studying their stellar populations. A new generation of population synthesis tools that we have been developing are now capable of measuring an unprecedented amount of information from high quality spectra of galaxies. In this talk I will present results from an ongoing program aimed at measuring the stellar initial mass function, ages, and detailed elemental abundance patterns of early-type galaxies over the interval 0<z<1. Constraints on the abundances of the alpha, iron peak, and neutron capture elements offer the promise of reconstructing the detailed star formation histories of these now dormant galaxies. By measuring the evolution of these quantities through cosmic time we are gaining fresh insights into the assembly histories of galaxies. The techniques we are developing will enable `extragalactic chemical tagging' and, more generally, will open up the low resolution universe for detailed study
Charlie Conroy (Harvard Smithsonian Center Astrophys., Cambridge)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
One of the primary avenues for understanding the formation and evolution of galaxies is through studying their stellar populations. A new generation of population synthesis tools that we have been developing are now capable of measuring an unprecedented amount of information from high quality spectra of galaxies. In this talk I will present results from an ongoing program aimed at measuring the stellar initial mass function, ages, and detailed elemental abundance patterns of early-type galaxies over the interval 0<z<1. Constraints on the abundances of the alpha, iron peak, and neutron capture elements offer the promise of reconstructing the detailed star formation histories of these now dormant galaxies. By measuring the evolution of these quantities through cosmic time we are gaining fresh insights into the assembly histories of galaxies. The techniques we are developing will enable `extragalactic chemical tagging' and, more generally, will open up the low resolution universe for detailed study
2015-04-21
17:15
17:15
Simulating the formation and evolution of the galaxy population
Simon White (MPIA Garching)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Recent observations of the high-redshift universe have characterized the initial conditions for nonlinear structure formation over the full range of scales responsible for dwarf and giant galaxies, galaxy clusters and the large-scale cosmic web. At the same time, wide-field spectroscopic and photometric surveys have measured the abundance and clustering of low-redshift galaxies as a function of mass, size, morphology, kinematic structure, gas content, metallicity, star formation rate and nuclear activity, while deep surveys have explored the evolution of several of these distributions to z>3. Galaxy population simulations aim to interpret these observations within the LCDM structure formation paradigm, thereby constraining the complex, diverse and heavily interconnected astrophysics of galaxy formation. Recent simulations are broadly consistent with the galaxy abundances and clustering seen in both wide-field and deep surveys, and provide predictions for topics as different as galaxy-galaxy lensing, the triggering and duty cycles of AGN, and the evolution of Tully-Fisher, mass-size and mass-metallicity relations. They show galaxy assembly histories to be strongly constrained by the structure formation paradigm, giving insight into issues such as internally versus externally driven evolution, inflow versus winds, major versus minor mergers, in situ versus ex situ star formation, and disks versus bulges. In addition, simulations can now be adapted to represent any chosen LCDM-like cosmology, allowing a first assessment of whether galaxy formation uncertainties will limit our ability to do precision cosmology with galaxy surveys.
Simon White (MPIA Garching)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Recent observations of the high-redshift universe have characterized the initial conditions for nonlinear structure formation over the full range of scales responsible for dwarf and giant galaxies, galaxy clusters and the large-scale cosmic web. At the same time, wide-field spectroscopic and photometric surveys have measured the abundance and clustering of low-redshift galaxies as a function of mass, size, morphology, kinematic structure, gas content, metallicity, star formation rate and nuclear activity, while deep surveys have explored the evolution of several of these distributions to z>3. Galaxy population simulations aim to interpret these observations within the LCDM structure formation paradigm, thereby constraining the complex, diverse and heavily interconnected astrophysics of galaxy formation. Recent simulations are broadly consistent with the galaxy abundances and clustering seen in both wide-field and deep surveys, and provide predictions for topics as different as galaxy-galaxy lensing, the triggering and duty cycles of AGN, and the evolution of Tully-Fisher, mass-size and mass-metallicity relations. They show galaxy assembly histories to be strongly constrained by the structure formation paradigm, giving insight into issues such as internally versus externally driven evolution, inflow versus winds, major versus minor mergers, in situ versus ex situ star formation, and disks versus bulges. In addition, simulations can now be adapted to represent any chosen LCDM-like cosmology, allowing a first assessment of whether galaxy formation uncertainties will limit our ability to do precision cosmology with galaxy surveys.
2015-02-03
17:15
17:15
Fundamental Physics from Gravitational Lensing
Allen Heavens (Imperial College)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Allen Heavens (Imperial College)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
2015-01-27
17:15
17:15
The Search for Gravitational Waves
Bruce Allen (MPG-AEI)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
In 1916, Einstein predicted the existence of gravitational radiation, a fundamental consequence of his general theory of relativity. By the end of this decade, we expect to make the first direct observations of gravitational waves, using ground-based instruments (LIGO in the USA, VIRGO in Italy, GEO in Germany, KAGRA in Japan, LIGO in India). I describe the status and capabilities of the detectors, and discuss the different types of astrophysical sources which we hope to detect. We expect that the first direct detections of gravitational waves (perhaps as early as 2017) will be from the coalescence and merger of binary neutron star pairs. Such events may also be accompanied by electromagnetic gamma-ray bursts. I'll also talk about the longer-term perspectives, and describe how some of the new data analysis methods and technology developed for the gravitational wave search have benefited more conventional electromagnetic astronomy. For example in the past four years the volunteer distributed computing project Einstein@Home has discovered over fifty new radio and gamma-ray pulsars.
Bruce Allen (MPG-AEI)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
In 1916, Einstein predicted the existence of gravitational radiation, a fundamental consequence of his general theory of relativity. By the end of this decade, we expect to make the first direct observations of gravitational waves, using ground-based instruments (LIGO in the USA, VIRGO in Italy, GEO in Germany, KAGRA in Japan, LIGO in India). I describe the status and capabilities of the detectors, and discuss the different types of astrophysical sources which we hope to detect. We expect that the first direct detections of gravitational waves (perhaps as early as 2017) will be from the coalescence and merger of binary neutron star pairs. Such events may also be accompanied by electromagnetic gamma-ray bursts. I'll also talk about the longer-term perspectives, and describe how some of the new data analysis methods and technology developed for the gravitational wave search have benefited more conventional electromagnetic astronomy. For example in the past four years the volunteer distributed computing project Einstein@Home has discovered over fifty new radio and gamma-ray pulsars.
2015-01-20
17:15
17:15
The Cosmic Ionising Background: from the Reionsation Era to Present Days
Francesco Haardt (University of Milano)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Francesco Haardt (University of Milano)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
2015-01-13
17:15
17:15
Our Universe – Cosmological Results of the Planck Mission
Thorsten Enßlin (MPA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Thorsten Enßlin (MPA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
2014-12-16
17:15
17:15
Snowlines, Red Dwarfs, and Little Green Beings: A Cosmic Tale of Origins
Eric Gaidos (Hawaii)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The search for Earth-size and potentially Earth-like planets around other stars has entered a new era with the achievements of the Kepler mission and the promise of new astronomical capabilities in space and on the ground. Tiny M dwarf stars and their planets have played an out-sized role in the success of this endeavor, but their study is only now catching up with those of their solar-mass cousins. I review recent advances in measuring the properties of these stars as they relate to understanding their planets. It has been proposed that M dwarf stars host most of the "habitable real estate" in our Galaxy and thus, in a speculative vein, I discuss the potential of their planets to host life and why, if they are such attractive locales, we do not find ourselves orbiting one.
Eric Gaidos (Hawaii)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
The search for Earth-size and potentially Earth-like planets around other stars has entered a new era with the achievements of the Kepler mission and the promise of new astronomical capabilities in space and on the ground. Tiny M dwarf stars and their planets have played an out-sized role in the success of this endeavor, but their study is only now catching up with those of their solar-mass cousins. I review recent advances in measuring the properties of these stars as they relate to understanding their planets. It has been proposed that M dwarf stars host most of the "habitable real estate" in our Galaxy and thus, in a speculative vein, I discuss the potential of their planets to host life and why, if they are such attractive locales, we do not find ourselves orbiting one.
2014-12-09
17:15
17:15
The Complex Ends of Galaxy Lives: Star Formation, Black Hole Feedback and the Fate of Gas Reservoirs
Kevin Schawinski (ETH Zürich, Switzerland)
Heidelberg Joint Astronomical Colloquium
Phil 12, gHS
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Abstract
Massive galaxies are broadly split into those forming stars on the main sequence, and those which are quiescent. The physical processes by which galaxies quench their star formation remain poorly understood. I analyze the properties of galaxies and track their evolutionary trajectories as they migrate from the blue cloud of star forming galaxies to the red sequence of quiescent galaxies via the `green valley'. I show that there must be two fundamentally star formation quenching pathways associated with early- and late-type galaxies which are intricately linked to how hydrogen gas reservoirs are destroyed or shut off. In the quenching of late-type galaxies, environment (or halo mass) is a key parameter, while for early-types, an internal mechanism such as black hole feedback is more likely. I will present recent HI observations supporting this picture.
Kevin Schawinski (ETH Zürich, Switzerland)
Heidelberg Joint Astronomical Colloquium
Phil 12, gHS
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Abstract
Massive galaxies are broadly split into those forming stars on the main sequence, and those which are quiescent. The physical processes by which galaxies quench their star formation remain poorly understood. I analyze the properties of galaxies and track their evolutionary trajectories as they migrate from the blue cloud of star forming galaxies to the red sequence of quiescent galaxies via the `green valley'. I show that there must be two fundamentally star formation quenching pathways associated with early- and late-type galaxies which are intricately linked to how hydrogen gas reservoirs are destroyed or shut off. In the quenching of late-type galaxies, environment (or halo mass) is a key parameter, while for early-types, an internal mechanism such as black hole feedback is more likely. I will present recent HI observations supporting this picture.
2014-12-02
17:15
17:15
Observing Magnetic Fields in Galaxies and Prospects with the Square Kilometre Array
Rainer Beck (MPIfR)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The strength and structure of cosmic magnetic fields can be well studied by observations of radio continuum emission, its polarization and Faraday rotation. Total field strengths in spiral arms and bars are 10-30 MicroGauss and hence are dynamically important. These probably are turbulent fields generated by turbulent gas motions. Fields with a well-ordered spiral structure exist in many types of galaxies. The strongest regular fields are found in interarm regions, sometimes forming 'magnetic spiral arms' between the optical arms. Faraday rotation measures of the polarization vectors sometimes reveals large-scale patterns which are regarded as signatures of coherent fields generated by dynamos. Polarization observations with the forthcoming large radio telescopes is opening a new era in the observation of magnetic fields and should help to understand their origin. Low-frequency radio synchrotron emission traces low-energy cosmic-ray electrons which can propagate further away from their origin. LOFAR (operating at 30-240 MHz) started to map the structure of weak magnetic fields in the outer regions and halos of galaxies and in the Milky Way. Polarization at higher frequencies (1-10 GHz), to be observed with the JVLA and the SKA, traces magnetic fields in the disks and central regions of galaxies in unprecedented detail. All-sky surveys of Faraday rotation measures towards a dense grid of polarized background sources planned the SKA and its precursor telescope ASKAP are dedicated to measure magnetic fields in distant intervening galaxies, clusters and intergalactic filaments. These surveys will also be used to model the overall structure and strength of the magnetic field in our Milky Way.
Rainer Beck (MPIfR)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The strength and structure of cosmic magnetic fields can be well studied by observations of radio continuum emission, its polarization and Faraday rotation. Total field strengths in spiral arms and bars are 10-30 MicroGauss and hence are dynamically important. These probably are turbulent fields generated by turbulent gas motions. Fields with a well-ordered spiral structure exist in many types of galaxies. The strongest regular fields are found in interarm regions, sometimes forming 'magnetic spiral arms' between the optical arms. Faraday rotation measures of the polarization vectors sometimes reveals large-scale patterns which are regarded as signatures of coherent fields generated by dynamos. Polarization observations with the forthcoming large radio telescopes is opening a new era in the observation of magnetic fields and should help to understand their origin. Low-frequency radio synchrotron emission traces low-energy cosmic-ray electrons which can propagate further away from their origin. LOFAR (operating at 30-240 MHz) started to map the structure of weak magnetic fields in the outer regions and halos of galaxies and in the Milky Way. Polarization at higher frequencies (1-10 GHz), to be observed with the JVLA and the SKA, traces magnetic fields in the disks and central regions of galaxies in unprecedented detail. All-sky surveys of Faraday rotation measures towards a dense grid of polarized background sources planned the SKA and its precursor telescope ASKAP are dedicated to measure magnetic fields in distant intervening galaxies, clusters and intergalactic filaments. These surveys will also be used to model the overall structure and strength of the magnetic field in our Milky Way.
2014-11-25
17:15
17:15
Gas and Galaxy Evolution: From Voids to Clusters, Near and Far
Jacqueline van Gorkom (Columbia)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Jacqueline van Gorkom (Columbia)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
2014-11-18
17:15
17:15
Has Dark Matter Finally Been Found?
Lars Bergstrom (Stockholm)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
In the last couple of years, several claims of hints of dark matter detection have been made. In this talk, I will give a brief review of the dark matter problem and present the large spectrum of theoretical particle candidate models, as well as their various detection methods. Current indications of dark matter detection will be discussed, and arguments both for and against the dark matter interpretation of these will be given. Finally, I will attempt to answer the question in the title.
Lars Bergstrom (Stockholm)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
In the last couple of years, several claims of hints of dark matter detection have been made. In this talk, I will give a brief review of the dark matter problem and present the large spectrum of theoretical particle candidate models, as well as their various detection methods. Current indications of dark matter detection will be discussed, and arguments both for and against the dark matter interpretation of these will be given. Finally, I will attempt to answer the question in the title.
2014-11-11
17:15
17:15
The Cradles of Planets – Turbulent Gas Disks around Young Stars
Hubert Klahr (MPIA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
Planets are a beneficial side effect of star formation. They are believed to form in the dust rich gas disk around young stars. These essentially Keplerian disks have proven to be extremely stable to perturbations, when magnetic fields are not in operation, as we believe it is the case for large portions of a typical circumstellar disk. But disks around young stars are complicated entities - they share a lot of properties with planetary atmospheres and one can learn a lot from the stability of rotating stars. Disks around young stars have a radial temperature gradient driven by stellar irradiation, which leads to a thermal wind, e.g. vertical shear. In addition the temperature gradient leads to a height dependent radial stratification that can be radially buoyant. Without thermal relaxation these disks are linearly stable, but with the right amount of cooling and heating for instance by the radiative transport of heat, one can drive a Goldreich-Schubert-Fricke Instability (see for instance Nelson et al 2013) and a Convective Overstability (Klahr and Hubbard 2014; Lyra 2014). In this talk I present some recent results from linear stability analysis as well as from numerical experiments and discuss the consequences on the planet formation process and its observational signatures.
Hubert Klahr (MPIA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
Planets are a beneficial side effect of star formation. They are believed to form in the dust rich gas disk around young stars. These essentially Keplerian disks have proven to be extremely stable to perturbations, when magnetic fields are not in operation, as we believe it is the case for large portions of a typical circumstellar disk. But disks around young stars are complicated entities - they share a lot of properties with planetary atmospheres and one can learn a lot from the stability of rotating stars. Disks around young stars have a radial temperature gradient driven by stellar irradiation, which leads to a thermal wind, e.g. vertical shear. In addition the temperature gradient leads to a height dependent radial stratification that can be radially buoyant. Without thermal relaxation these disks are linearly stable, but with the right amount of cooling and heating for instance by the radiative transport of heat, one can drive a Goldreich-Schubert-Fricke Instability (see for instance Nelson et al 2013) and a Convective Overstability (Klahr and Hubbard 2014; Lyra 2014). In this talk I present some recent results from linear stability analysis as well as from numerical experiments and discuss the consequences on the planet formation process and its observational signatures.
2014-11-04
17:15
17:15
Nuclear Star Clusters and Black Holes
Nadine Neumayer (MPIA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The centers of massive galaxies are special in many ways, not least because all of them are believed to host supermassive black holes. Since the discovery of a number of relations linking the mass of this central black hole to the large scale properties of the surrounding galaxy bulge it has been suspected that the growth of the central black hole is intimately connected to the evolution of its host galaxy. However, at lower masses, and especially for bulgeless galaxies, the situation is much less clear. Interestingly, these galaxies often host massive star clusters at their centers, and unlike black holes, these nuclear star clusters provide a visible record of the accretion of stars and gas into the nucleus. I will present our ongoing observing programme of the nearest nuclear star clusters, including the one in our Milky Way. These observations provide important information on the formation mechanism of nuclear star clusters. They allow us to measure potential black hole masses and might give a clue on how black holes get to the centres of galaxies.
Nadine Neumayer (MPIA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The centers of massive galaxies are special in many ways, not least because all of them are believed to host supermassive black holes. Since the discovery of a number of relations linking the mass of this central black hole to the large scale properties of the surrounding galaxy bulge it has been suspected that the growth of the central black hole is intimately connected to the evolution of its host galaxy. However, at lower masses, and especially for bulgeless galaxies, the situation is much less clear. Interestingly, these galaxies often host massive star clusters at their centers, and unlike black holes, these nuclear star clusters provide a visible record of the accretion of stars and gas into the nucleus. I will present our ongoing observing programme of the nearest nuclear star clusters, including the one in our Milky Way. These observations provide important information on the formation mechanism of nuclear star clusters. They allow us to measure potential black hole masses and might give a clue on how black holes get to the centres of galaxies.
2014-10-28
17:15
17:15
The Galactic Bulge: Current Perspective, New Surveys
Mike Rich (UCLA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The Galactic bulge of the Milky Way is the nearest spheroid, 100 times closer than the Andromeda galaxy. This offers a unique opportunity to investigate detailed kinematics, chemical composition, and structure for this population. Although the Lambda-CDM formalism gives a clear route to the formation of classical bulges, the Milky Way bulge appears to have formed from the secular evolution of a massive disk, a spheroid formation channel that does not easily follow from LCDM. A survey of 9,500 bulge M giants, the Bulge Radial Velocity Assay, showed that <10% of the bulge is in a classical slowly rotating bulge. The discovery that a strongly "X-shaped" component to the bulge is also present, strengthens the evidence for an extreme almost pure bar. Yet color-magnitude diagrams from HST, and composition, support an old, rapidly formed, bulge. We present new composition trends that support his picture and may also constrain the star formation history and initial mass function of the system. We also explore Terzan 5, a peculiar star cluster with multiple stellar populations, proposed as a fossil bulge "building block" stellar system. We will also present the plan for and early results from the Blanco DECam Bulge Survey, a six-color optical/infrared survey of the bulge, to map its structure as a function of age and metallicity.
Mike Rich (UCLA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
The Galactic bulge of the Milky Way is the nearest spheroid, 100 times closer than the Andromeda galaxy. This offers a unique opportunity to investigate detailed kinematics, chemical composition, and structure for this population. Although the Lambda-CDM formalism gives a clear route to the formation of classical bulges, the Milky Way bulge appears to have formed from the secular evolution of a massive disk, a spheroid formation channel that does not easily follow from LCDM. A survey of 9,500 bulge M giants, the Bulge Radial Velocity Assay, showed that <10% of the bulge is in a classical slowly rotating bulge. The discovery that a strongly "X-shaped" component to the bulge is also present, strengthens the evidence for an extreme almost pure bar. Yet color-magnitude diagrams from HST, and composition, support an old, rapidly formed, bulge. We present new composition trends that support his picture and may also constrain the star formation history and initial mass function of the system. We also explore Terzan 5, a peculiar star cluster with multiple stellar populations, proposed as a fossil bulge "building block" stellar system. We will also present the plan for and early results from the Blanco DECam Bulge Survey, a six-color optical/infrared survey of the bulge, to map its structure as a function of age and metallicity.
2014-10-21
17:15
17:15
The Origin of the Stellar Initial Mass Function
Mark Krumholz (UCSC)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
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Abstract
The mass distribution of newborn stars, known as the initial mass function (IMF), has a distinct peak at a mass slightly less than that of the Sun. This characteristic stellar mass appears to be nearly invariant across a huge range of star-forming environments, and over most of cosmic time. Explaining its origin and universality is one of the oldest problems in theoretical astrophysics, and a fully successful theory eludes us even today. In this talk, however, I describe recent progress toward an explanation for the mass scale of stars. This work is based on radiation-hydrodynamic simulations, which elucidate the way forming stars feed back on their environments and regulate the process of turbulent fragmentation that determines the IMF. Using insight from these simulations, I show that it may even be possible to express the characteristic mass of stars in terms of fundamental constants.
Mark Krumholz (UCSC)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, Großer Hörsaal
Show/hide abstract
Abstract
The mass distribution of newborn stars, known as the initial mass function (IMF), has a distinct peak at a mass slightly less than that of the Sun. This characteristic stellar mass appears to be nearly invariant across a huge range of star-forming environments, and over most of cosmic time. Explaining its origin and universality is one of the oldest problems in theoretical astrophysics, and a fully successful theory eludes us even today. In this talk, however, I describe recent progress toward an explanation for the mass scale of stars. This work is based on radiation-hydrodynamic simulations, which elucidate the way forming stars feed back on their environments and regulate the process of turbulent fragmentation that determines the IMF. Using insight from these simulations, I show that it may even be possible to express the characteristic mass of stars in terms of fundamental constants.
2014-07-22
17:00
17:00
Galaxies on FIRE: Stellar Feedback Explains Inefficient Star Formation
Philip Hopkins (Caltech Univ.)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Many of the most fundamental unsolved questions in star and galaxy formation revolve around star formation and "feedback" from both massive stars and accretion onto super-massive black holes. I'll present new simulations which attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, stellar winds, and photo-ionization. These mechanisms lead to 'self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law and the global inefficiency of star formation -- the stellar mass function -- emerge naturally. Within galaxies, feedback regulates the structure of the interstellar medium, and many observed properties of the ISM, star formation, and galaxies can be understood as a fundamental consequence of super-sonic turbulence in a rapidly cooling, self-gravitating medium. But feedback also produces galactic super-winds that can dramatically alter the cosmological evolution of galaxies, their behavior in galaxy mergers, and structure of the inter-galactic medium: these winds depend non-linearly on multiple feedback mechanisms in a way that explains why they have been so difficult to model in previous "sub-grid" approaches. Finally, I'll discuss how missing physics in these models might change our conclusions.
Philip Hopkins (Caltech Univ.)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
Show/hide abstract
Abstract
Many of the most fundamental unsolved questions in star and galaxy formation revolve around star formation and "feedback" from both massive stars and accretion onto super-massive black holes. I'll present new simulations which attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, stellar winds, and photo-ionization. These mechanisms lead to 'self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law and the global inefficiency of star formation -- the stellar mass function -- emerge naturally. Within galaxies, feedback regulates the structure of the interstellar medium, and many observed properties of the ISM, star formation, and galaxies can be understood as a fundamental consequence of super-sonic turbulence in a rapidly cooling, self-gravitating medium. But feedback also produces galactic super-winds that can dramatically alter the cosmological evolution of galaxies, their behavior in galaxy mergers, and structure of the inter-galactic medium: these winds depend non-linearly on multiple feedback mechanisms in a way that explains why they have been so difficult to model in previous "sub-grid" approaches. Finally, I'll discuss how missing physics in these models might change our conclusions.
2014-07-15
17:00
17:00
Planetary Science from the Top-Down: the Exoplanet Opportunity
Nick Cowan (Northwestern Univ.)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
What started as a trickle in the mid 1990's is now a torrent, with over one thousand extrasolar planets currently known, and thousands of candidates awaiting confirmation. The study of exoplanets has already revolutionized our view of planet formation, and will soon do the same to our understanding of planetary atmospheres and interiors. The diversity of exoplanets gives us the leverage to crack hard problems in planetary science: cloud formation, atmospheric circulation, plate tectonics, etc. However, the characterization of exoplanets presents a challenge familiar to astronomers: our targets are so distant that we only see them as unresolved dots. I will describe how we can extract spatially-resolved snapshots of planets from such observations. These data are sufficient to constrain low-order climate models and therefore give us insight into the effects of clouds, heat transport, and geochemical cycling. Coarse measurements for a large number of planets is the perfect complement to the detailed measurements possible in the Solar System. That is the exoplanet opportunity.
Nick Cowan (Northwestern Univ.)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
What started as a trickle in the mid 1990's is now a torrent, with over one thousand extrasolar planets currently known, and thousands of candidates awaiting confirmation. The study of exoplanets has already revolutionized our view of planet formation, and will soon do the same to our understanding of planetary atmospheres and interiors. The diversity of exoplanets gives us the leverage to crack hard problems in planetary science: cloud formation, atmospheric circulation, plate tectonics, etc. However, the characterization of exoplanets presents a challenge familiar to astronomers: our targets are so distant that we only see them as unresolved dots. I will describe how we can extract spatially-resolved snapshots of planets from such observations. These data are sufficient to constrain low-order climate models and therefore give us insight into the effects of clouds, heat transport, and geochemical cycling. Coarse measurements for a large number of planets is the perfect complement to the detailed measurements possible in the Solar System. That is the exoplanet opportunity.
2014-07-08
17:00
17:00
The turbulent life-cycle of molecular clouds
Stefanie Walch (Uni-Köln)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Apart from stellar feedback and self-gravityMolecular clouds are cold, dense, and turbulent filamentary structures that condense out of the multi-phase interstellar medium. They are also the sites of star formation. The minority of new-born stars is massive, but these stars are particularly important for the fate of their parental molecular clouds. I will present results from high-performance, three-dimensional simulations that show the formation and dispersal of molecular clouds within representative pieces of disk galaxies., we employ an accurate description of gas heating and cooling as well as a small chemical network including molecule formation and self-shielding. Gravitational collapse is compensated by stellar feedback, leading to the establishment of a dynamical equilibrium of the interstellar medium within the disk. I will discuss results for disks at different gas surface densities which e.g. demonstrate that the molecular gas mass fraction increases with gas surface density. Moreover, I will show that outflows generated by supernovae that explode within the parental molecular clouds may contain a significant fraction of diffuse molecular hydrogen that is not well traced by CO. These simulations will bring forth a modern paradigm for the full life cycle of molecular clouds with important implications for galaxy evolution.
Stefanie Walch (Uni-Köln)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Apart from stellar feedback and self-gravityMolecular clouds are cold, dense, and turbulent filamentary structures that condense out of the multi-phase interstellar medium. They are also the sites of star formation. The minority of new-born stars is massive, but these stars are particularly important for the fate of their parental molecular clouds. I will present results from high-performance, three-dimensional simulations that show the formation and dispersal of molecular clouds within representative pieces of disk galaxies., we employ an accurate description of gas heating and cooling as well as a small chemical network including molecule formation and self-shielding. Gravitational collapse is compensated by stellar feedback, leading to the establishment of a dynamical equilibrium of the interstellar medium within the disk. I will discuss results for disks at different gas surface densities which e.g. demonstrate that the molecular gas mass fraction increases with gas surface density. Moreover, I will show that outflows generated by supernovae that explode within the parental molecular clouds may contain a significant fraction of diffuse molecular hydrogen that is not well traced by CO. These simulations will bring forth a modern paradigm for the full life cycle of molecular clouds with important implications for galaxy evolution.
2014-07-01
17:00
17:00
Very high energy gamma ray astronomy: from H.E.S.S. to CTA
Werner Hofmann (MPI Kernphys, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
In the last decade, very high energy (VHE) gamma ray astronomy - at photon energies of 100 GeV and beyond - has developed in giant steps, with the number of known cosmic VHE gamma ray sources now well over 100. As the first system of large imaging atmospheric Cherenkov telescopes, the High Energy Stereoscopic System - H.E.S.S. - in Namibia has contributed significantly to this development. The talk will highlight some of the key results, and provide an outlooks towards the planned CTA observatory, aimed at boosting sensitivity by an order of magnitude compared to H.E.S.S.
Werner Hofmann (MPI Kernphys, Heidelberg)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
In the last decade, very high energy (VHE) gamma ray astronomy - at photon energies of 100 GeV and beyond - has developed in giant steps, with the number of known cosmic VHE gamma ray sources now well over 100. As the first system of large imaging atmospheric Cherenkov telescopes, the High Energy Stereoscopic System - H.E.S.S. - in Namibia has contributed significantly to this development. The talk will highlight some of the key results, and provide an outlooks towards the planned CTA observatory, aimed at boosting sensitivity by an order of magnitude compared to H.E.S.S.
2014-06-24
17:00
17:00
The chemistry of planet formation
Karin Öberg (CfA)
Heidelberg Joint Astronomical Colloquium
MPIA, Königstuhl, Auditorium
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Abstract
In the cold and dense stages of star and planet formation, volatile molecules condense out on interstellar grains forming icy mantles. The physics and chemistry of these ices may have a direct impact on planet formation efficiencies and planet bulk compositions. Ice chemistry is also expected to be the main formation site of complex organics in space and may thus regulate the prebiotic potential of nascent planets. We have used a combination of IR and millimeter observations, theory, and laboratory experiments to characterize interstellar ices, snow line locations (i.e. where these ices are located), and the chemical and planet formation consequences of the exact locations of different snow lines. I will discuss how the outcome of these studies have impacted our understanding of ice processes and of organic chemistry during star and planet formation, and also future prospects as complete ALMA and the next generation of laboratory experiments come online.
Karin Öberg (CfA)
Heidelberg Joint Astronomical Colloquium
MPIA, Königstuhl, Auditorium
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Abstract
In the cold and dense stages of star and planet formation, volatile molecules condense out on interstellar grains forming icy mantles. The physics and chemistry of these ices may have a direct impact on planet formation efficiencies and planet bulk compositions. Ice chemistry is also expected to be the main formation site of complex organics in space and may thus regulate the prebiotic potential of nascent planets. We have used a combination of IR and millimeter observations, theory, and laboratory experiments to characterize interstellar ices, snow line locations (i.e. where these ices are located), and the chemical and planet formation consequences of the exact locations of different snow lines. I will discuss how the outcome of these studies have impacted our understanding of ice processes and of organic chemistry during star and planet formation, and also future prospects as complete ALMA and the next generation of laboratory experiments come online.
2014-06-17
17:00
17:00
Extracting science from surveys of our Galaxy: the balance between dark & light matter from the RAdial Velocity Experiment
James Binney (Oxford University)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Huge observational resources are being devoted to the study of our Galaxy. Dynamical models of the Galaxy are key to the exploitation of data from these surveys, and the surveys in hand demand a step change in the sohistication of available dynamical models. I will review the state of this art and then discuss the application of the new methods to data for 200,000 giant stars observed by RAVE. These data enable us to split the matter that generates the gravitational field near the sun into dark and light components with negligible random error. The uncertainties are systematic and of order 10%. The dominant uncertainty is the distance scale of the sample, and this will be eliminated by Gaia in the next few years.
James Binney (Oxford University)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Huge observational resources are being devoted to the study of our Galaxy. Dynamical models of the Galaxy are key to the exploitation of data from these surveys, and the surveys in hand demand a step change in the sohistication of available dynamical models. I will review the state of this art and then discuss the application of the new methods to data for 200,000 giant stars observed by RAVE. These data enable us to split the matter that generates the gravitational field near the sun into dark and light components with negligible random error. The uncertainties are systematic and of order 10%. The dominant uncertainty is the distance scale of the sample, and this will be eliminated by Gaia in the next few years.
2014-06-10
17:00
17:00
Observing the Dark Universe
Catherine Heymans (Inst. Astron., Univ Edinburgh)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Dark Matter and Dark Energy constitute over 95% of the energy density of the Universe, and determining the nature of the Dark Universe is one of the major challenges for science over the next decade. Weak gravitational lensing is a powerful technique that can map dark matter structures from its gravitational effects alone and probe dark energy through its effect on the growth of these structures. From an observational prospective, I'll discuss the challenges and successes of this unique technique, presenting results from the completed Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) and the new ESO-VST Kilo-Degree Survey (KiDS). These surveys probe dark matter in galaxy haloes and galaxy clusters and constrain cosmology through the detection of weak lensing by large-scale structures. In combination with galaxy redshift surveys, lensing also provides a unique test for whether we need to go beyond Einstein with our current model of gravity.
Catherine Heymans (Inst. Astron., Univ Edinburgh)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Dark Matter and Dark Energy constitute over 95% of the energy density of the Universe, and determining the nature of the Dark Universe is one of the major challenges for science over the next decade. Weak gravitational lensing is a powerful technique that can map dark matter structures from its gravitational effects alone and probe dark energy through its effect on the growth of these structures. From an observational prospective, I'll discuss the challenges and successes of this unique technique, presenting results from the completed Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) and the new ESO-VST Kilo-Degree Survey (KiDS). These surveys probe dark matter in galaxy haloes and galaxy clusters and constrain cosmology through the detection of weak lensing by large-scale structures. In combination with galaxy redshift surveys, lensing also provides a unique test for whether we need to go beyond Einstein with our current model of gravity.
2014-06-03
17:00
17:00
Making gold in core-collapse supernovae and neutron star mergers
Almudena Arcones (Inst. Kernphys, TU Darmstadt)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
Almudena Arcones (Inst. Kernphys, TU Darmstadt)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
2014-05-27
17:00
17:00
The Peripheries of Galaxies: Dim but not Dull
Annette Ferguson (Univ. Edinburgh)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Evidence is mounting for the presence of complex low surface brightness structures in the outer regions of galaxies. While the most spectacular examples are provided by systems hosting coherent debris streams, the most common examples may be extremely diffuse stellar envelopes. Wide-field imagers on large telescopes are allowing us to quantitatively explore the resolved stellar populations in these components within and well beyond the Local Group. I will highlight some recent results from our work and discuss the insight these outer structures provide on understanding massive galaxy assembly. I will also discuss how we are using deep HST studies of M31's outer regions to probe its evolutionary history in unprecedented detail.
Annette Ferguson (Univ. Edinburgh)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Evidence is mounting for the presence of complex low surface brightness structures in the outer regions of galaxies. While the most spectacular examples are provided by systems hosting coherent debris streams, the most common examples may be extremely diffuse stellar envelopes. Wide-field imagers on large telescopes are allowing us to quantitatively explore the resolved stellar populations in these components within and well beyond the Local Group. I will highlight some recent results from our work and discuss the insight these outer structures provide on understanding massive galaxy assembly. I will also discuss how we are using deep HST studies of M31's outer regions to probe its evolutionary history in unprecedented detail.
2014-05-20
17:00
17:00
Astronomical probes of fundamental constants
Paolo Molaro (Obs. Astron. Trieste)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
Do the fundamental constants of nature vary over cosmological time and/or distance scales? This question goes into the heart of both cosmology and particle physics since several theories beyond the Standard Model or a quintessence dark energy allow for varying of physical constants. Absorption lines recorded by intervening galaxies in the spectra of distant QSOs are "barcodes" of atomic structures and can probe the variability of constants such as the fine structure constant and the proton-to-electron mass ratio. The current observational claims of a spatial dipole will be critically reviewed and the first results of the ESO Large Program presented. In particular, we will discuss the efforts to reveal possible systematic in the wavelength calibration of the most used spectrographs. The status of the ESPRESSO project for the incoherent combined focus of the VLT will be also briefly described.
Paolo Molaro (Obs. Astron. Trieste)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
Show/hide abstract
Abstract
Do the fundamental constants of nature vary over cosmological time and/or distance scales? This question goes into the heart of both cosmology and particle physics since several theories beyond the Standard Model or a quintessence dark energy allow for varying of physical constants. Absorption lines recorded by intervening galaxies in the spectra of distant QSOs are "barcodes" of atomic structures and can probe the variability of constants such as the fine structure constant and the proton-to-electron mass ratio. The current observational claims of a spatial dipole will be critically reviewed and the first results of the ESO Large Program presented. In particular, we will discuss the efforts to reveal possible systematic in the wavelength calibration of the most used spectrographs. The status of the ESPRESSO project for the incoherent combined focus of the VLT will be also briefly described.
2014-05-16
17:00
17:00
Ice Cube and the Discovery of High-Energy Cosmic Neutrinos
Francis Halzen (Univ. Wisconsin)
Heidelberg Joint Astronomical Colloquium
INF 227, Otto Haxel Saal
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Abstract
NOTE: This is a joint colloquium between the "Physikalisches Kolloquium" and the "Heidelberg Joint Astronomy Colloquium" and it takes place on Friday in the INF 227
Francis Halzen (Univ. Wisconsin)
Heidelberg Joint Astronomical Colloquium
INF 227, Otto Haxel Saal
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Abstract
NOTE: This is a joint colloquium between the "Physikalisches Kolloquium" and the "Heidelberg Joint Astronomy Colloquium" and it takes place on Friday in the INF 227
2014-05-06
17:00
17:00
Solar System formation and evolution
Alessandro Morbidelli (Observatory of Nice)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
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Abstract
The discovery of over 1,000 extrasolar planets reveals a huge diversity of planetary system architectures, even when restricting the sample to the sole giant planets. We see many Jovian planets at distances from the parent stars comparable to those of our terrestrial planets or even much smaller (hot Jupiters), as well as on orbits with a variety of eccentricities, ranging up to almost unity. These wild and surprising orbits are usually explained invoking two processes: planet migration and planet instabilities. Then, the question arises on whether our Solar System experienced these processes as well and why its structure looks so different from those of the giant planet extrasolar systems discovered so far. Luckily, we have a huge number of observational constraints that can guide us to reconstruct with some confidence the evolution of the Solar System back to the time of giant planet formation. A non-exhaustive list of constraints is made of: the orbits of the giant planets (non-resonant, partially eccentric and inclined), the Earth/Mars dichotomy (mass ratio, formation timescales), the asteroid belt (depleted, excited, featuring 2 distinct populations partially mixed, accretion within 3My, less than 10Gy-equivalent collisional evolution), Jupiter’s Trojans (extremely strong dynamical excitation, L4/L5 asymmetry), the irregular satellites populations (similar for all giant planets once rescaled to the planet’s Hill radius), the Kuiper belt (complex structure with cold, hot, resonant and scattered populations), the Oort cloud (its large population, compared to the Kuiper belt), the Late Heavy Bombardment of the Moon. I will present a model that can explain the global structure of the Solar System, consistent with all constraints listed above. If this model is correct, it suggests that the specific structure of the Solar System is due to some specific and fortuitous events that happened during its evolution. Changing slightly these events produces, through a chaotic propagation of effects, radically different final systems which cover a wide portion of the observed diversity of planetary systems.
Alessandro Morbidelli (Observatory of Nice)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomy, Königstuhl, Auditorium
Show/hide abstract
Abstract
The discovery of over 1,000 extrasolar planets reveals a huge diversity of planetary system architectures, even when restricting the sample to the sole giant planets. We see many Jovian planets at distances from the parent stars comparable to those of our terrestrial planets or even much smaller (hot Jupiters), as well as on orbits with a variety of eccentricities, ranging up to almost unity. These wild and surprising orbits are usually explained invoking two processes: planet migration and planet instabilities. Then, the question arises on whether our Solar System experienced these processes as well and why its structure looks so different from those of the giant planet extrasolar systems discovered so far. Luckily, we have a huge number of observational constraints that can guide us to reconstruct with some confidence the evolution of the Solar System back to the time of giant planet formation. A non-exhaustive list of constraints is made of: the orbits of the giant planets (non-resonant, partially eccentric and inclined), the Earth/Mars dichotomy (mass ratio, formation timescales), the asteroid belt (depleted, excited, featuring 2 distinct populations partially mixed, accretion within 3My, less than 10Gy-equivalent collisional evolution), Jupiter’s Trojans (extremely strong dynamical excitation, L4/L5 asymmetry), the irregular satellites populations (similar for all giant planets once rescaled to the planet’s Hill radius), the Kuiper belt (complex structure with cold, hot, resonant and scattered populations), the Oort cloud (its large population, compared to the Kuiper belt), the Late Heavy Bombardment of the Moon. I will present a model that can explain the global structure of the Solar System, consistent with all constraints listed above. If this model is correct, it suggests that the specific structure of the Solar System is due to some specific and fortuitous events that happened during its evolution. Changing slightly these events produces, through a chaotic propagation of effects, radically different final systems which cover a wide portion of the observed diversity of planetary systems.
2014-04-29
17:00
17:00
Transition: When protoplanetary disks reveal their planetary system
Carsten Dominik (University of Amsterdam)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomie, Auditorium
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Abstract
Protoplanetary disks are the cradles of planetary systems. I will discuss new insights that have come together through observations and modeling of disks around Herbig Ae stars, which are nearby young stars surrounded by protoplanetary disks. Recently we have learned that a subclass of these objects, earlier thought to be the less evolved group, all seem to be transitional disks characterised by large gaps and possibly in the process of shedding the disk and revealing the embedded planetary systems. I will discuss both recent observations and modelling efforts to trace the processes in these disks and to try to retrieve information about embedded (proto) planets by looking gap sizes, shapes, and separation of different grains sizes.
Carsten Dominik (University of Amsterdam)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomie, Auditorium
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Abstract
Protoplanetary disks are the cradles of planetary systems. I will discuss new insights that have come together through observations and modeling of disks around Herbig Ae stars, which are nearby young stars surrounded by protoplanetary disks. Recently we have learned that a subclass of these objects, earlier thought to be the less evolved group, all seem to be transitional disks characterised by large gaps and possibly in the process of shedding the disk and revealing the embedded planetary systems. I will discuss both recent observations and modelling efforts to trace the processes in these disks and to try to retrieve information about embedded (proto) planets by looking gap sizes, shapes, and separation of different grains sizes.
2014-04-22
17:00
17:00
From classical celestial mechanics to modern stellar dynamics in Astronomy
Roberto Capuzzo Dolcetta (Dep. of Physics, Sapienza, Univ. Rome)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomie, Auditorium
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Abstract
Gravitation is the pervasive engine of astronomical phenomena over all the space scales. The newtonian, classic, gravitational N-body problem is one of the archetipes of complex problems in Physics and has many applications in Astrophysics, from the study of planetary motion to the dynamics of stellar clusters and galaxies up to galaxy clusters. This problem has been studied under both theoretical and numerical points of view and the development of modern software and hardware is nowadays opening new horizons in the understanding of many observed features of the local and far Universe. In this Colloquium I will briefly resume some of the basics of this topic and present an update on recent applications and results, especially of the dynamics of very crowded regions around the massive and super massive black holes in galactic centers.
Roberto Capuzzo Dolcetta (Dep. of Physics, Sapienza, Univ. Rome)
Heidelberg Joint Astronomical Colloquium
Haus der Astronomie, Auditorium
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Abstract
Gravitation is the pervasive engine of astronomical phenomena over all the space scales. The newtonian, classic, gravitational N-body problem is one of the archetipes of complex problems in Physics and has many applications in Astrophysics, from the study of planetary motion to the dynamics of stellar clusters and galaxies up to galaxy clusters. This problem has been studied under both theoretical and numerical points of view and the development of modern software and hardware is nowadays opening new horizons in the understanding of many observed features of the local and far Universe. In this Colloquium I will briefly resume some of the basics of this topic and present an update on recent applications and results, especially of the dynamics of very crowded regions around the massive and super massive black holes in galactic centers.
2014-02-04
17:15
17:15
New Insights into The Virgo Cluster
Laura Ferrarese (NRC Herzberg Institute of Astrophysics, Canada)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
At a distance of 16.5 Mpc and with a gravitating mass of 4.2×10^14 solar masses, the Virgo Cluster is the dominant mass concentration in the local universe, the centre of the Local Supercluster, and the largest concentration of galaxies within ~35 Mpc. With thousands of member galaxies lying at a nearly common distance and spanning virtually all known morphological types, it has historically played a key role in studies of how galaxies form and evolve in dense environments. It is, without question, the most thoroughly studied cluster of galaxies in the universe, and remains a preferred target for a systematic survey of baryonic substructures in the low-redshift universe. In this talk, I will present results from the Next Generation Virgo Cluster Survey (NGVS), an ambitious optical imaging survey of the Virgo cluster carried out using the MegaPrime instrument at the Canada France Hawaii Telescope (CFHT), and supplemented with spectroscopic data from Keck, Gemini, MMT, VLT and AAT. Specifically, I will focus on 1) the use of globular clusters as baryonic tracers of the cluster potential; 2) the structure of galaxies and their dark matter content; and 3) the faint end of the galaxy luminosity function and the occupation fraction of low-mass dark matter haloes. Some details about the NGVS can be gathered from the survey webpage: https://www.astrosci.ca/NGVS/The_Next_Generation_Virgo_Cluster_Survey/Home.html
Laura Ferrarese (NRC Herzberg Institute of Astrophysics, Canada)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
At a distance of 16.5 Mpc and with a gravitating mass of 4.2×10^14 solar masses, the Virgo Cluster is the dominant mass concentration in the local universe, the centre of the Local Supercluster, and the largest concentration of galaxies within ~35 Mpc. With thousands of member galaxies lying at a nearly common distance and spanning virtually all known morphological types, it has historically played a key role in studies of how galaxies form and evolve in dense environments. It is, without question, the most thoroughly studied cluster of galaxies in the universe, and remains a preferred target for a systematic survey of baryonic substructures in the low-redshift universe. In this talk, I will present results from the Next Generation Virgo Cluster Survey (NGVS), an ambitious optical imaging survey of the Virgo cluster carried out using the MegaPrime instrument at the Canada France Hawaii Telescope (CFHT), and supplemented with spectroscopic data from Keck, Gemini, MMT, VLT and AAT. Specifically, I will focus on 1) the use of globular clusters as baryonic tracers of the cluster potential; 2) the structure of galaxies and their dark matter content; and 3) the faint end of the galaxy luminosity function and the occupation fraction of low-mass dark matter haloes. Some details about the NGVS can be gathered from the survey webpage: https://www.astrosci.ca/NGVS/The_Next_Generation_Virgo_Cluster_Survey/Home.html
2014-01-28
17:15
17:15
Star formation in the Magellanic clouds as seen by low mass stars
Guido De Marchi (European Space Agency, Noordwijk, Netherlands)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We have undertaken a systematic study of pre-main-sequence (PMS) stars spanning a wide range of masses (0.5 - 4 Msun), metallicities (0.1 - 1 Zsun) and ages (0.5 - 30 Myr). We have used the Hubble Space Telescope to identify and characterise a large sample of PMS objects in several star forming regions in the Magellanic Clouds, namely 30 Dor, the SN1987A field and NGC1850 in the LMC and NGC 346 and NGC 602 in the SMC, and have compared them to PMS stars in similar regions in the Milky Way, such as NGC 3603 and Trumpler 14. Thanks to a novel method that we have developed to combine broad-band (V,I) photometry with narrow-band Halpha imaging, we have determined the physical parameters (temperature, luminosity, age, mass and mass accretion rate) of more than 3000 bona-fide PMS stars still undergoing active mass accretion. This is presently the largest and most homogeneous sample of PMS objects with known physical properties and it includes not only very young objects, but also PMS stars older than 10-20 Myr that are approaching the main sequence. I will present the main results of this research, including the fact that the mass accretion rate scales roughly with the inverse of the cube root of the metallicity and is therefore systematically higher in the Magellanic Clouds than in the Milky Way for stars of the same mass and age. These results are bound to have important implications for, and constraints on our understanding of the star formation process.
Guido De Marchi (European Space Agency, Noordwijk, Netherlands)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We have undertaken a systematic study of pre-main-sequence (PMS) stars spanning a wide range of masses (0.5 - 4 Msun), metallicities (0.1 - 1 Zsun) and ages (0.5 - 30 Myr). We have used the Hubble Space Telescope to identify and characterise a large sample of PMS objects in several star forming regions in the Magellanic Clouds, namely 30 Dor, the SN1987A field and NGC1850 in the LMC and NGC 346 and NGC 602 in the SMC, and have compared them to PMS stars in similar regions in the Milky Way, such as NGC 3603 and Trumpler 14. Thanks to a novel method that we have developed to combine broad-band (V,I) photometry with narrow-band Halpha imaging, we have determined the physical parameters (temperature, luminosity, age, mass and mass accretion rate) of more than 3000 bona-fide PMS stars still undergoing active mass accretion. This is presently the largest and most homogeneous sample of PMS objects with known physical properties and it includes not only very young objects, but also PMS stars older than 10-20 Myr that are approaching the main sequence. I will present the main results of this research, including the fact that the mass accretion rate scales roughly with the inverse of the cube root of the metallicity and is therefore systematically higher in the Magellanic Clouds than in the Milky Way for stars of the same mass and age. These results are bound to have important implications for, and constraints on our understanding of the star formation process.
2014-01-21
17:15
17:15
Supernova remnants colliding with molecular clouds: From TeV to meV emission
Thierry Montmerle (Institut d'Astrophysique de Paris, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
It is now well established that a class of gamma-ray sources in the galactic plane, especially in the TeV range as seen by HESS and other Cerenkov telescopes, and in the GeV range by the Fermi and AGILE satellites, is associated with intermediate-age supernova remnants interacting with molecular clouds in massive star-forming regions. After a brief general introduction linking high-energy gamma-rays and the origin of cosmic rays, I will focus on a few such gamma-ray sources (W28, W44, and W51) and the challenging conclusions that can be drawn from them. I will then describe our recent work on related submm measurements and consequences of enhanced ionizing effects in molecular clouds due to locally accelerated low-energy cosmic rays. I will also mention briefly some implications for the "cradle of the Sun" and for the high-energy evolution of OB associations. Work done in collaboration with Cecilia Ceccarelli, Guillaume Dubus, Pierre Hily-Brant, and Solenn Vaupré (Institut de Planétologie et d’Astrophysique de Grenoble, France)
Thierry Montmerle (Institut d'Astrophysique de Paris, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
It is now well established that a class of gamma-ray sources in the galactic plane, especially in the TeV range as seen by HESS and other Cerenkov telescopes, and in the GeV range by the Fermi and AGILE satellites, is associated with intermediate-age supernova remnants interacting with molecular clouds in massive star-forming regions. After a brief general introduction linking high-energy gamma-rays and the origin of cosmic rays, I will focus on a few such gamma-ray sources (W28, W44, and W51) and the challenging conclusions that can be drawn from them. I will then describe our recent work on related submm measurements and consequences of enhanced ionizing effects in molecular clouds due to locally accelerated low-energy cosmic rays. I will also mention briefly some implications for the "cradle of the Sun" and for the high-energy evolution of OB associations. Work done in collaboration with Cecilia Ceccarelli, Guillaume Dubus, Pierre Hily-Brant, and Solenn Vaupré (Institut de Planétologie et d’Astrophysique de Grenoble, France)
2014-01-14
17:15
17:15
Testing the Theory of the Early Universe using the Cosmic Microwave Background
Eiichiro Komatsu (Max-Planck-Institut für Astrophysik, Garching, Germany)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Cosmic Microwave Background (CMB), the fossil light of the Big Bang, is the oldest light that one can ever hope to observe in our Universe. The CMB provides us with a direct image of the Universe when it was still an "infant" - 380,000 years old - and has enabled us to obtain a wealth of cosmological information, such as the composition, age, geometry, and history of the Universe. Yet, can we go further and learn about the primordial universe, when it was much younger than 380,000 years old, perhaps as young as a tiny fraction of a second? If so, this gives us a hope to test competing theories about the origin of the Universe at ultra high energies. In this talk I present the final results from nine years of observations using the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and discuss future prospects on our quest to probe the physical condition of the very early Universe.
Eiichiro Komatsu (Max-Planck-Institut für Astrophysik, Garching, Germany)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Cosmic Microwave Background (CMB), the fossil light of the Big Bang, is the oldest light that one can ever hope to observe in our Universe. The CMB provides us with a direct image of the Universe when it was still an "infant" - 380,000 years old - and has enabled us to obtain a wealth of cosmological information, such as the composition, age, geometry, and history of the Universe. Yet, can we go further and learn about the primordial universe, when it was much younger than 380,000 years old, perhaps as young as a tiny fraction of a second? If so, this gives us a hope to test competing theories about the origin of the Universe at ultra high energies. In this talk I present the final results from nine years of observations using the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and discuss future prospects on our quest to probe the physical condition of the very early Universe.
2014-01-07
17:15
17:15
What can we learn from the observations of gravitational waves?
Hyung Mok Lee (Seoul National University, Republic of Korea)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Hyung Mok Lee (Seoul National University, Republic of Korea)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
2013-12-17
17:15
17:15
The formation and evolution of massive star forming disks
Reinhard Genzel (Max-Planck-Institut für extraterrestrische Physik, München, Germany)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Reinhard Genzel (Max-Planck-Institut für extraterrestrische Physik, München, Germany)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
2013-12-10
17:15
17:15
Booms, Burps & Bumps: The Dynamic Universe
Shri Kulkarni (California Institute of Technology, Pasadena, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
That occasionally new sources ("Stella Nova") would pop up in the heavens was noted more than a thousand years ago. The earnest study of cosmic explosions began in earnest less than a hundred years ago. Over time astronomers have come to appreciate the central role of supernovae in synthesizing new elements (and making life as we know possible). The Palomar Transient Factory (PTF), an innovative 2-telescope system, was designed to explicitly to chart the transient sky with a particular focus on events which lie in the nova-supernova gap. PTF can find an extragalactic transient every 20 minutes and a Galactic (strong) variable every 10 minutes. The results so far: classification of 2000 supernovae, identification of an emerging class of ultra-luminous supernovae, the earliest discovery of a Ia supernovae, discovery of luminous red novae, the most comprehensive UV spectroscopy of Ia supernovae, discovery low energy budget supernovae, clarification of sub-classes of core collapse and thermo-nuclear explosions, mapping of the systematics of core collapse supernovae, identification of a trove of eclipsing binaries and the curious AM CVns.
Shri Kulkarni (California Institute of Technology, Pasadena, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
That occasionally new sources ("Stella Nova") would pop up in the heavens was noted more than a thousand years ago. The earnest study of cosmic explosions began in earnest less than a hundred years ago. Over time astronomers have come to appreciate the central role of supernovae in synthesizing new elements (and making life as we know possible). The Palomar Transient Factory (PTF), an innovative 2-telescope system, was designed to explicitly to chart the transient sky with a particular focus on events which lie in the nova-supernova gap. PTF can find an extragalactic transient every 20 minutes and a Galactic (strong) variable every 10 minutes. The results so far: classification of 2000 supernovae, identification of an emerging class of ultra-luminous supernovae, the earliest discovery of a Ia supernovae, discovery of luminous red novae, the most comprehensive UV spectroscopy of Ia supernovae, discovery low energy budget supernovae, clarification of sub-classes of core collapse and thermo-nuclear explosions, mapping of the systematics of core collapse supernovae, identification of a trove of eclipsing binaries and the curious AM CVns.
2013-12-03
17:15
17:15
The gas content of galaxies at z<0.2
Jarle Brinchmann (Leiden Observatory, Netherlands)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Jarle Brinchmann (Leiden Observatory, Netherlands)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
2013-11-26
17:15
17:15
Precision Cosmic Ray Physics with AMS on the International Space Station
Roberto Battiston (Trento University, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Two years after the launch and begin of operation of AMS on the ISS, precision measurements of cosmic rays composition and spectra are presented. We will discuss the implications of these results on issues ranging from the physics of dark-matter to the physics of cosmic ray composition and acceleration mechanisms as well as the future perspectives.
Roberto Battiston (Trento University, Italy)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Two years after the launch and begin of operation of AMS on the ISS, precision measurements of cosmic rays composition and spectra are presented. We will discuss the implications of these results on issues ranging from the physics of dark-matter to the physics of cosmic ray composition and acceleration mechanisms as well as the future perspectives.
2013-11-19
17:15
17:15
The growth of massive black holes
Marta Volonteri (Institut d'Astrophysique de Paris, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Massive black holes, weighing millions to billions of solar masses, inhabit the centers of today's galaxies. The progenitors of these black holes powered luminous quasars within the first billion years of the Universe. The first massive black holes must therefore have formed around the time the first stars and galaxies formed and then evolved along with their hosts for the past thirteen billion years. I will discuss some aspects of the cosmic evolution of massive black holes, from their formation to their growth and the interplay between black holes and galaxies.
Marta Volonteri (Institut d'Astrophysique de Paris, France)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
Massive black holes, weighing millions to billions of solar masses, inhabit the centers of today's galaxies. The progenitors of these black holes powered luminous quasars within the first billion years of the Universe. The first massive black holes must therefore have formed around the time the first stars and galaxies formed and then evolved along with their hosts for the past thirteen billion years. I will discuss some aspects of the cosmic evolution of massive black holes, from their formation to their growth and the interplay between black holes and galaxies.
2013-11-12
17:15
17:15
The vast polar structures around the Milky Way and Andromeda, and the implications thereof for fundamental physics
Pavel Kroupa (Universität Bonn, Germany)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Milky Way has been found to have a rotating vast polar disk-like structure of radius larger than 200kpc and half thickness of about 15 kpc. Andromeda, too, harbors a disk of satellite galaxies, which is, however, even thinner. It is also rotating. The only reasonable explanation for these structures is for them to have formed from tidal material expelled when the Milky Way and Andromeda interacted about 10Gyr ago, either with each other or with other galaxies. The implications of this for gravitational physics would be profound, because the high dynamical M/L ratios of the satellite galaxies in the structures could not stem from dark matter.
Pavel Kroupa (Universität Bonn, Germany)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The Milky Way has been found to have a rotating vast polar disk-like structure of radius larger than 200kpc and half thickness of about 15 kpc. Andromeda, too, harbors a disk of satellite galaxies, which is, however, even thinner. It is also rotating. The only reasonable explanation for these structures is for them to have formed from tidal material expelled when the Milky Way and Andromeda interacted about 10Gyr ago, either with each other or with other galaxies. The implications of this for gravitational physics would be profound, because the high dynamical M/L ratios of the satellite galaxies in the structures could not stem from dark matter.
2013-11-05
17:15
17:15
The Fast Track to Finding an Inhabited Exoplanet
David Charbonneau (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The investigation of planets orbiting other stars has moved from the study of gas giants to the hunt for smaller planets that are predominantly rock and ice in composition. When such planets are discovered in edge-on orbits, such that the planet and star undergo mutual eclipses, we are granted the opportunity to determine directly the planetary masses and sizes. Most interestingly, we can study starlight filtered through the planetary atmosphere to deduce its chemical composition, and perhaps even search for biosignatures. I will summarize the most recent results from the NASA Kepler Mission and describe two surveys intended to find the closest habitable exoplanet.
David Charbonneau (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
The investigation of planets orbiting other stars has moved from the study of gas giants to the hunt for smaller planets that are predominantly rock and ice in composition. When such planets are discovered in edge-on orbits, such that the planet and star undergo mutual eclipses, we are granted the opportunity to determine directly the planetary masses and sizes. Most interestingly, we can study starlight filtered through the planetary atmosphere to deduce its chemical composition, and perhaps even search for biosignatures. I will summarize the most recent results from the NASA Kepler Mission and describe two surveys intended to find the closest habitable exoplanet.
2013-10-29
17:15
17:15
The Inner Lives of Stars: Asteroseismology, Stellar Physics, and Stellar Populations
Marc Pinsonneault (Ohio State University, Columbus, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
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Abstract
We are entering a new era of precision stellar astrophysics. Large surveys and upcoming missions, such as Gaia, promise a wealth of high-quality observational data. Asteroseismology is now possible for bulk stellar populations, as demonstrated by both the Kepler and CoRoT missions. I review the basic properties of asteroseismology, focusing on two distinct classes of results: Planet and stellar population studies will benefit enormously from inferences about basic stellar properties (such as mass, radius, and age) from the non-radial frequency patterns in stars, and this data will permit a fundamental calibration of stellar models in the mass plane. A detailed study of the oscillation frequencies also permits stringent tests of stellar physics, and I will demonstrate how important internal features (such as core mass, density, and rotation) are now observables. I finish with an overview of the broad range of applications of precision stellar astrophysics.
Marc Pinsonneault (Ohio State University, Columbus, USA)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Show/hide abstract
Abstract
We are entering a new era of precision stellar astrophysics. Large surveys and upcoming missions, such as Gaia, promise a wealth of high-quality observational data. Asteroseismology is now possible for bulk stellar populations, as demonstrated by both the Kepler and CoRoT missions. I review the basic properties of asteroseismology, focusing on two distinct classes of results: Planet and stellar population studies will benefit enormously from inferences about basic stellar properties (such as mass, radius, and age) from the non-radial frequency patterns in stars, and this data will permit a fundamental calibration of stellar models in the mass plane. A detailed study of the oscillation frequencies also permits stringent tests of stellar physics, and I will demonstrate how important internal features (such as core mass, density, and rotation) are now observables. I finish with an overview of the broad range of applications of precision stellar astrophysics.
2013-10-22
17:15
17:15
Cosmology as a laboratory for neutrino physics
Steen Hannestad (Aarhus University, Denmark)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
Steen Hannestad (Aarhus University, Denmark)
Heidelberg Joint Astronomical Colloquium
Philosophenweg 12, großer Hörsaal
