19/12/19 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Shedding light on gas around galaxies across cosmic time
Michele Fumagalli (Durham University)
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The evolution of galaxies is closely connected to the gas environment in which galaxies reside. Traditionally, this tenuous gas that cycles in and out of galaxies has been studied primarily in absorption using quasar spectroscopy. The deployment of large integral field spectrographs at 8 meter telescopes, and in particular MUSE at VLT, is now transforming our view of the interplay between the ambient gas and galaxies by enabling spectroscopy in emission at very low surface brightness. In this talk, I will present highlights from multiple large programmes that are starting to shed light onto the link between gas and galaxies as a function of cosmic time.
Talk — First results from the KATRIN experiment and the search for sterile neutrinos
Susanne Mertens (TUM)
The Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to directly probe the neutrino mass with a sensitivity of 0.2 eV (90% CL). KATRIN persues a model-independent approach, solely based on the kinematics of tritium beta decay. In spring 2019 KATRIN performed its first neutrino mass measurement campaign. With this first data set new limits on the neutrino mass could be established, reaching for the first time the sub-eV regime. In this talk these results and the future scientific program of KATRIN to search for sterile neutrinos will be presented.
Talk — Witnessing the Growth of Structure through X-ray Observations of Clusters of Galaxies
Esra Bulbul (MPE)
Galaxy clusters, the most massive collapsed structures in the Universe residing at the connecting nods of the Cosmic Web, are unique probes for exploring the evolution of baryons, nature of dark matter, and constraining cosmological parameters of the Universe. X-ray observations of clusters of galaxies provide insights into overall structure of the Universe by capturing bulk of the baryons from small spatial scales to the cosmological Large Scale Structure. In this talk, I will review the recent advancements in understanding of the structure and evolution of baryons from cluster cores to outskirts as well understanding the nature of dark matter in these massive reservoirs of dark matter. In addition, I will highlight the significance of ongoing all-sky survey with eROSITA on-board the Spektr-RG X-ray observatory in revolutionizing the cluster astrophysics and cosmology.
Talk — The role of AGN-feedback in the baryon cycle of z~2 galaxies
Vincenzo Mainieri (ESO)
Theoretical arguments suggest that the energy released by the black hole at the center of most galaxies may play an important role in shaping the properties of the interstellar medium (so-called AGN feedback). In particular, AGN-driven, galaxy wide massive outflows may not be a rare and peculiar phenomenon, but a fundamental process affecting the bulk of the baryons in the universe. Hundreds of hours of observations from the ground have been used in the last decade to characterize such outflows and their impact on the host galaxies using e.g. NIR IFU on 8-10m telescopes to trace the ionized gas or the molecular phase with ALMA.
I will report on the first results of a recently completed Large Programme with SINFONI/VLT (SUPER) on a sample of AGN at z~2. SUPER aims to address the following questions: a) demography of AGN driven outflows on a statistical sample of AGN at cosmic noon; b) how the properties (e.g. energetics and geometry) of such outflows are connected with the properties of the central SMBH; c) which is the impact of such outflows on the gas content of the host galaxy.
I will finally describe further developments in this research area using facilities that will become available in the future (e.g. JWST, ELTs, SKA, Athena).
Talk — Quantum black hole from Standard Physics
Gerard 't Hooft (Utrecht University)
When, in theoretical physics, we attempt to derive the quantum properties of a black hole, several difficulties are found on our way. In this talk it is shown how these difficulties can be overcome, but not without reformulating some of the laws of nature. This is very important to know, because this way one might uncover new features of the gravitational force when subject to the laws of quantum mechanics.
We claim that the evolution operator for the quantum black hole during short time intervals can be deduced unambiguously from standard quantum field theory in curved space-time, merely by demanding unitarity and completeness for pure quantum states. We explain its Hilbert space and the topologically non-trivial space-time that emerges in our approach. Since there are no run-away solutions, the behaviour at arbitrarily long time scales follows unambiguously. Curiously, string theory does not seem to work flawlessly when details at the Planck scale are addressed.
Talk — The core of the matter – spatially resolving the nuclei of Active Galaxies with VLTI/GRAVITY
Eckhard Sturm (MPE)
One of the most exciting opportunities offered by the new VLT beam combiner GRAVITY is to directly resolve the immediate regions around the super-massive black holes (SMBHs) in the center of active galaxies (AGN), i.e. the Broad Line Region (BLR) and the hot dust ("torus") structures. We are exploiting this capability to study the inner workings of AGN in the K-band on unprecedented micro-arcsecond (sub-pc) spatial scales. This has led to the first interferometric detection of a BLR (finding ordered rotation and measuring the black hole mass in the quasar 3C273), as well as to the first 0.2 parsec resolution K-band image of the dust sublimation region in the nucleus of the Seyfert 2 galaxy NGC1068 (finding a ring-like structure which is inconsistent with the expected signatures of a geometrically and optically thick torus). I will summarize these and other recent results , discuss their scientific (and historical) context, and give and outlook how such observations (along with already planned or potential future upgrades of GRAVITY) might contribute to the study of the structures and physical processes around SMBHs or to the study of how SMBHs build up their mass across cosmic time.
Talk — The sky at metre wavelengths: from exoplanets to galaxy clusters
Francesco de Gasperin (Hamburger Sternwarte)
The lower edge of the radio window (10-200 MHz) has been scarcely explored due to the complexity of such observations. In this talk I will review the recent progresses in the observation of the metre-wavelength sky, focusing on the last results obtained with the Low Frequency Array (LOFAR). Then, I will summarize the recent scientific outcomes obtained with LOFAR observations. From the search for radio emission from exoplanets, to the AGN life-cycle, to the study of diffuse radio emission in galaxy clusters. I will conclude presenting the first data release of the LOFAR 2m sky survey at 150 MHz and an sneak preview of the upcoming LOFAR LBA Sky Survey at 50 MHz.
Talk — The Hubble Frontier Fields & BUFFALO surveys : (Some of) what you can do with massive galaxy clusters
Mathilde Jauzac (Durham University)
The outskirts of clusters make the best, and most efficient locations to observe and trace the mass assembly processes of the Cosmic Web. Residing at the vertices of this Cosmic Web (Bond et al. 1996), galaxy clusters grow by steady accretion of matter from the surroundings, as well as by discrete mergers with nearby groups and clusters. Supported by simulations, this scenario regarding the total mass content and distribution in filaments themselves remains largely untested. Filaments are vital elements of the cosmic census, containing up to half the baryonic mass of the Universe as a 'warm hot intergalactic medium' but also the majority of the dark matter.
Recently, some of the most massive and disturbed clusters have been the centre of attention thanks to the Hubble Frontier Fields (HFF) initiative, which constitutes the largest commitment ever of Hubble Space Telescope (HST) time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters. These clusters were chosen for their strong lens properties, and are all highly disturbed objects, showing major and minor merging on-going processes, making them ideal target to trace the Cosmic Web assembly.
While combining strong- and weak-lensing regimes to map the total mass with X-rays observations of the hot gas and spectroscopy of cluster galaxies to look at their direction of motion, we can thus study the dynamical scenarios in place within these massive galaxy clusters, and trace the substructures engaged in these processes. I will present the last results we obtained on the HFF clusters, and discuss the different caveats present on both the observing and simulation sides. I will then present the BUFFALO HST large programme, the 'spatial extension' of the HFF, that started back in July 2018 and should end in June 2020.
Talk — The Transient Universe: Cosmic Explosions and Dark Energy
Mark Sullivan (University of Southampton)
Type Ia supernovae have long been used as probes of the expansion history of the universe. Their standardisable luminosities make them very attractive as distance measures, and they remain indispensable in constraining the properties of dark energy. In this talk, I will give an update from the Dark Energy Survey (DES), including the latest cosmological results using type Ia supernovae to measure the dark energy equation-of-state. I'll also show how large imaging surveys, such as DES, are developing our knowledge of the 'zoo' of cosmic explosions, beyond the classical supernova types. I'll focus on two new classes of explosion: superluminous supernovae, ultra-bright explosions now confirmed out to a redshift of two, and which bring the possibility of measuring distances at higher redshifts than type Ia supernovae; and 'calcium-rich transients', faint-and-fast events that play a critical role in chemical enrichment, and have a surprisingly high intrinsic rate. Finally, I will look forward to what the next decade of LSST and massive spectroscopic follow-up may bring.
Talk — The Evolution of Multiple-Star Systems
Adrian Hamers (MPA)
The direct detection of gravitational waves from merging black holes by LIGO in 2015 has revitalized the area of gravitational wave astrophysics. The origin of black hole and neutron star mergers is still unclear, however, and various scenarios have been proposed. In this talk, I focus on the evolution of multiple-star systems such as triples, quadruples, and binary systems in galactic nuclei. I discuss the complex interplay between dynamical, stellar, and binary processes in these systems. Finally, I highlight future directions for modeling their long-term evolution, in order to make predictions for future gravitational wave observations.
Talk — Very Long Baseline Interferometry at mm Wavelengths: Imaging Event Horizon Scale Structures
Anton Zensus (Max Planck Institute for Radio Astronomy)
The first image of the shadow of a supermassive black hole located in the core of the galaxy Messier 87 was recently released by the Event Horizon Telescope (EHT) Collaboration. This image is a high point following decades of VLBI (Very Long Baseline Interferometry) observations of Active Galactic Nuclei (AGN) and relativistic jet structures. VLBI at mm wavelengths enables the study of the conditions and interactions close to supermassive black holes on a range of scales. I will give an overview of this research in the context of astrophysical studies of AGN. Finally, I will give an outlook to the future of this research at Event Horizon scales.
Talk — What Processes Shape our Milky Way's Disk?
Hans-Walter Rix (MPIA, Heidelberg)
It is often said that the Milky Way can serve as a 'model organism' to explore and understand the physical mechanism that shape galaxies from random initial fluctuations into the beautiful island universes we see today.
This statement is true, but easily said and much harder to make a reality. Over the last years I have collaborated with a number of students, post-docs and visitors at MPIA combining spectral surveys and now Gaia to turn this Galactic Archeology mantra into astrophysical insights.
In this talk I will synthesize some of this effort, focusing on two aspects of our Galaxy's main component, its disk: what sets the overall radial profile of the disk, and what sets its vertical structure? The answers to both questions are linked to the question of how much dynamical memory loss our Galaxy has incurred -- its exceptionally quiescent history. I believe we are now considerably closer to understanding why disk galaxies look the way they do.
Talk — Galaxy Cluster Evolution over the Past 10 Billion Years
Michael McDonald (MIT Kavli Institute)
In recent years, the number of known galaxy clusters at high redshift has grown dramatically thanks in large part to the success of surveys utilizing the Sunyaev Zel'dovich effect. In particular, surveys carried out by the South Pole Telescope have facilitated the discovery of hundreds of new distant clusters, allowing us to trace, for the first time, the evolution of clusters from shortly after their collapse (z~2) to present day (z~0). In this talk, I will highlight recent efforts by our group to understand the observed evolution in the most massive clusters, including: the enrichment history of the intracluster medium, the merging history of clusters, the cooling and formation of cool cores, the growth of central cluster galaxies, and the evolution of the central radio-loud AGN. In addition, I will attempt summarize the current state of ongoing and planned SPT surveys, and the synergies with current and future observatories including eRosita and Athena.
Talk — Chemical evolution of the Milky Way
Else Starkenburg (Leibniz-Institut für Astrophysik Potsdam)
The Milky Way halo consists of old and metal-poor stars amidst bound substructures such as globular clusters and satellite dwarf galaxies. A comparison of stellar abundance ratios and kinematics between typical halo stars and these bound substructures reveals many interesting patterns that give us clues about their chemical evolution - a process called Galactic archaeology. The lowest metallicity stars that still exist today probably carry the imprint of very few supernova and push Galactic archaeology to its limits. These stars represent our best observational approach to understand the First Stars and the early Galaxy. In this talk I will review cosmological modelling predictions for observations of these very old and metal-poor stars as well as observational efforts and results. 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 successfully for the very rare extremely metal-poor stars, to study metal-poor dwarf galaxies, and to search for stellar structures in the halo.
Talk — Decoding the Magnetic Universe
Sui Ann Mao (Max Planck Institute for Radioastronomy)
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 Spare Kilometre Array pathfinders and the next generation radio telescopes.
Talk — Exoplanet Atmosphere Characterization, Present and Future
Laura Kreidberg (CfA Harvard)
We now know that exoplanets abound in the Galaxy, with most stars hosting at least one planet. These recently discovered worlds are much more diverse than the planets in the Solar System, and raise many questions about their formation, evolution, and habitability. To address these questions, we turn to atmosphere characterization, which provides a wealth of additional information about the planets. I will discuss the state of the art in atmosphere studies, focusing on recent high-precision, space-based observations of hot Jupiters and warm Neptunes. These studies have already revealed planetary atmospheric chemistry, climate, and cloud coverage in unprecedented detail, and they are poised for a revolutionary advance thanks to a series of new and upcoming missions. I will conclude with a discussion of prospects for characterization of temperate, terrestrial worlds with future facilities.
Talk — Gaia's view of the Milky Way halo
Vasily Belokurov (University of Cambridge)
It was always hoped that one day we would be able to use Gaia data to pin down the matter distribution in the Milky Way, measure the Galactic accretion history, find new previously unseen dwarf galaxies with unprecedentedly low surface brightnesses and track narrow stellar streams to gauge masses of Dark Matter sub-halos. I will show that all of these hopes came true with the last year's Gaia Data Release 2.
Talk — The empirical bases of the SN-GRB connection
Massimo Della Valle (INAF, Osservatorio Astronomico di Capodimonte)
We review the status of the Supernova/Gamma-Ray Burst connection. Several pieces of evidence suggest that long duration Gamma-ray Bursts (GRBs) are associated with type Ic Supernovae (SNe). Current estimates of SN and GRB rates show that only a tiny fraction of massive stars, likely less than 2%, are able to produce GRBs. The reasons for this small ratio will be discussed.
Talk — Quasar-driven winds in galaxy formation
Nadia Zakamska (Johns Hopkins University)
Quasars are now thought to have made critical impact on galaxy formation. Feedback from accretion onto supermassive black holes is frequently implicated in establishing the black hole mass vs galaxy bulge correlations and in limiting the maximal mass of galaxies. In this talk, I will review the indirect evidence for quasar feedback as required by galaxy formation models. I will then review the recent progress on detecting direct evidence for quasar-driven outflows and other types of feedback through multi-wavelength observations. These data may provide direct observational evidence for one of the long-standing paradigms in galaxy formation.
Talk — Neutral and molecular gas outflows as tracers of the impact of radio jets
Raffaella Morganti (ASTRON, the Netherlands Institute for Radio Astronomy & Kapteyn Astronomical Institute, University of Groningen)
Our view of the gas and its physical conditions in the central region of AGN has been enriched by the discover of fast and massive outflows of HI and molecular gas. These outflows can be driven by radiation/winds but also by the interaction of the radio plasma with the ISM. Understanding the origin and quantifying their impact requires to trace their location and derive their physical conditions (density of the gas, mass, mass outflow rate and kinetic energy of the outflow etc.). Particularly interesting has been the finding that in the first phase of their life, jet in radio galaxies can be particularly effective in driving such outflows. This crucial phase is at the heart of the idea of feedback, therefore particularly relevant for studying feedback in action.
In this talk, I will present some of the results we have obtained to trace jet-driven HI and molecular gas outflows down to scales ranging from hundred to tens of pc. The impact of low-power radio jets will be discussed and the comparison with the predictions from numerical simulations will also be presented. Outflows of up to 100 Msun/yr have been found in molecular gas using ALMA while the HI observed with VLBI is showing that the outflowing gas is clumpy as also predicted from numerical simulations. I will describe the kinematics of the gas and its conditions and the relevance they may have for feedback.
Talk — Solar interior, helioseismology and neutrinos
Aldo Serenelli (CSIC, Barcelona)
For more than 20 years helioseismology, the study of solar oscillations, has provided an exquisite picture of the solar interior structure. However these oscillations, which are standing acoustic waves in the solar interior, have diminishing amplitudes towards the deep interior and render a blurred picture of the solar innermost core, where most nuclear reactions take place and neutrinos are produced. During the last decade, after the discovery of neutrino oscillations, solar neutrino experiments such as SuperKamiokande, SNO and especially Borexino have continued to develop and improve the accuracy and precision of measurements solar neutrino fluxes. Helioseismic and neutrino constraints offer complementary views of solar interiors and open up the best possibilities to date for testing solar (and stellar) evolution theory as well as a laboratory for particle physics.
The talk will first review the current status of (standard) solar modeling in the context of helioseismic constraints, and discuss where problems and uncertainties lie. About the latter, some emphasis will be placed on recent calculations and experiments of radiative opacities that impact solar and stellar modeling. The second part of the talk will present results of solar neutrino experiments, focusing on Borexino's capabilities to perform solar neutrino spectroscopy, and the constraints on solar interior models that can be obtained. The third part of the talk will briefly discuss the relevance of solar model uncertainties for evolution of low mass stars and the uncertainties in determination of stellar properties based on asteroseismic results might be affected. A short final part will include a discussion of the recent claims of detection of gravity modes (g-modes) in solar oscillations.
Talk — The conditions and impact of star formation in a multi-phase interstellar medium
Stefanie Walch (University of Cologne)
Star formation takes place in the densest and coldest parts of the interstellar medium (ISM), in dark molecular clouds. These are swept up by multiple supernova explosions on scales of several hundred parsec. While condensing out of the warm ISM, the clouds are continuously fed with fresh gas. Thus, the turbulent substructure and magnetic field properties are imprinted during cloud formation. The formation of dense clouds from the multi-phase ISM, the onset of star formation, and the evolution of the molecular clouds under the impact of stellar feedback from newly born massive stars is studied in high-resolution simulations within the SILCC project. In this talk I will give an overview of the physics and chemistry involved in molecular cloud formation and evolution. After the onset of star formation, the latter is governed by stellar feedback from newly born massive stars. The detailed cloud substructure determines the clouds' vulnerability to stellar feedback processes, in particular to ionizing radiation. Moreover, the ionization state of the gas can be highly variable on scales of tens of parsec due to small-scale turbulent motions within the star-forming clouds, which shield and release the ionizing radiation. This leads to a flickering of the young HII regions on the scale of ~10 pc. On scales of several 100 pc and time scales of tens of Mega-years, the combined feedback from star clusters leads to a reduced star formation rate, such that long depletion time scales are observed.
Talk — The Imaging X-ray Polarimetry Explorer (IXPE)
Martin C. Weisskopf (NASA's Marshall Space Flight Center)
It has been over 44 years since the last extra-solar X-ray polarization observation was performed. As part of the NASA's Small Explorer Program a new, exciting mission, will, for the first time, produce image-resolved polarimetry of astronomical sources. I am the Principal Investigator of this mission which includes a significant collaboration with the Italian Space Agency. I shall review the history of astrophysical X-ray polarimetry, discussing various experimental techniques and emphasizing the successful method of tracking the photoelectron in a low-Z gas developed in Italy that has allowed this experiment to proceed. After a discussion of the Observatory and its components, I shall present examples of the scientific advances that can be made by adding imaging polarimetry to the X-ray astronomer's arsenal of tools for probing diverse questions such as: Was the black hole at the center of the Milky Way galaxy one million times more active a few hundred years ago? What is the spin the black holes in microquasars? Is there direct evidence for the effects of quantum electrodynamics in the strong magnetic fields in magnetars?
Talk — Extragalactic Planetary Nebulae: kinematic tracers in and around galaxies
Magda Arnaboldi (ESO)
Extragalactic Planetary Nebulae (Pne) were mostly studied as secondary distance indicators in late and early-type galaxies, because of the cut-off of their luminosity function at bright magnitudes. With the use of 8 meter and custom built instruments of 4 meter telescopes, they become excellent spatial and kinematic tracers of their parent stellar populations. In this talk, I will begin with the latest results on the kinematics within galaxies and give examples for the maximal disk in NGC 628 and multiple disk components in M31. I will then move to the results from the extended Planetary Nebulae Spectrograph (e.PN.S) survey of a sample of local elliptical galaxies (ETGs). While ETGs are either fast and slow rotators at 1 R_e, their stellar halos traced by Pne show an increased kinematical diversity. By using extended velocity fields out to 5.6 R_e on average, evidence is found for a kinematic transition between inner regions and halos, which depends on the stellar mass and correlates with the spatial transition from the ``in-situ'' to the ``ex-situ'' components from cosmological simulations of galaxy formation. I will then present the results based on the kinematics of the halos using Pne for the high mass end of the galaxy population: the cD galaxies in groups and clusters. I will describe how their stellar halos fade into the intra-group/intracluster light and the current measurements of their orbital anisotropy at 50-100 kpc. I will conclude with the constraints on the satellite progenitors of the stars in the outermost regions of these halos/ICL and with a forward look for the use of the ELT.
Talk — Why Circumgalactic Matter Matters for Galaxy Evolution
Jessica K. Werk (University of Washington)
The circumgalactic medium (CGM; non-ISM gas within a galaxy virial radius) regulates the gas flows that shape the evolutionary paths of galaxies. It likely contains most of the metals lost in galaxy winds and enough material to sustain star-formation for billions of years. Owing to the vastly improved capabilities in space-based UV spectroscopy with the installation of HST/COS, observations and simulations of the CGM have emerged as the new frontier of galaxy evolution studies. In this talk, I will describe observational constraints we have placed on the origin and fate of this material by studying the gas kinematics, metallicity and ionization state of gas 10 - 200 kpc from galaxies' stars. I will conclude by introducing several exciting new techniques for resolving the gaseous structures in the CGM, and by posing unanswered questions about the CGM that will be addressed with future survey data and hydrodynamic simulations in a cosmological context.
Talk — Chemical Characterization of Extrasolar Planets
Nikku Madhusudhan (Institute of Astronomy, University of Cambridge)
Exoplanetary discoveries in the past two decades have unveiled an astonishing diversity in the physical characteristics of exoplanetary systems, including their orbital properties, masses, radii, equilibrium temperatures, and stellar hosts. Exoplanets known today range from gas-giants to nearly Earth-size planets, and some even in the habitable zones of their host stars. Recent advances in exoplanet observations and theoretical methods are now leading to unprecedented constraints on the physicochemical properties of exoplanetary atmospheres, interiors, and their formation conditions.
I will discuss the latest developments and future prospects of this new era of exoplanetary characterization. In particular, I will present some of the latest constraints on atmospheric chemical compositions of exoplanets, made possible by state-of-the-art high-precision observations from space and ground, and their implications for atmospheric processes and formation conditions of exoplanets. The emerging framework for using atmospheric elemental abundance ratios for constraining +the origins and migration pathways of giant exoplanets will be discussed along with their implications for smaller rocky planets. A survey of theoretical and observational directions in the field will be presented along with several open questions on the horizon.
Talk — The New Era of Stellar Physics
Matteo Cantiello (Flatiron Institute, New York)
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 in 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 the 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.
Talk — Stellar Population Models
Claudia Maraston (University of Portsmouth)
Stellar population synthesis models describing the energetic emission and stellar mass distribution of galaxies and star clusters are the essential analysis tool in astrophysics and cosmology. They are used to determine the physics of stellar systems (formation ages, star formation history and chemical composition) and dark matter fractions from data, to predict the spectral energy distribution of simulated galaxies, to trace cosmic time for constraining cosmological parameters , to predict the number, mass and location of stellar remnants giving origin to gravitational waves. Given their widespread use and core role, the accuracy of population synthesis models needs to be constantly improved for keeping pace with progress in instrumentation.
In this talk I shall appraise the progress made over the past two decades focusing on the most significant leaps - the treatment of late stages of stellar evolution and the inclusion of detailed chemistry - which starting from Munich have stimulated substantial work around the globe. I shall then introduce the next step in population model calculations, which will leverage the exploitation of current and future data and hopefully provide the solution to some current puzzles, including the universality of the Initial Mass Function.
Talk — Cosmic and other Bell Tests
Anton Zeilinger (Institute for Quantum Optics and Quantum Information Austrian Academy of Sciences and University of Vienna)
In experiments on Bell's theorem the possibility is tested whether local realistic explanations of the correlations between entangled particles can explain the observed correlations. In the talk, I will first discuss possible loopholes in tests of Bell's Inequalities. I will then focus on the so-called freedom of choice loophole. This loophole is related to the demand that the measurements of correlations on two (or in principle more) entangled particles are free and independent. I will then in detail report on tests of Bell's Inequality where cosmic sources are used to provide independent random input for the measurements t entangled photons. In the first experiment, stars within our Milky Way were used and in the second one, distant quasars. Another experiment has used choices of random numbers by humans. These numbers were directed to 13 experiments located globally at 12 different places. Finally, I will briefly mention the implementation of quantum cryptography between Europe and China using the Chinese quantum satellite Micius.
Talk — Forming Realistic Galaxies: Successes and Challenges
Alyson Brooks (Rutgers, the State University of New Jersey)
Just a decade ago it was believed that one could not form realistic dwarf or disk galaxies in cosmological simulations. The past decade has seen immense progress, through both advances in resolution and development of physically motivated feedback models. Different simulators are generally now capable of forming realistic galaxies that match a wide variety of observed galaxy scaling relations, despite variations in adopted star formation and feedback recipes.
I will discuss the reasons for these successes, but also highlight a couple of areas where simulators are still facing challenges, e.g., in reproducing realistic galaxy bulges. I will also show that the assumptions simulators have adopted in the classical dwarf regime will lead to widely varying predictions for the properties of ultra-faint dwarf galaxies. Finally, I will highlight future observations that have the potential to tightly constrain the physical conditions required for star formation at the earliest times.
Talk — Raining on Galaxies and Black Holes: Unifying the Micro and Macro Properties of AGN Feeding and Feedback
Massimo Gaspari (Princeton University)
Feeding and feedback tied to supermassive black holes (SMBHs) play central role in the cosmic evolution of galaxies, groups, and clusters of galaxies. The self-regulated active galactic nucleus (AGN) cycle is matter of intense debate. I review key results of our numerical campaign to unveil how SMBHs are tightly coupled to the multiphase gaseous halos, linking the inner gravitational radius to the large Mpc scale and vice versa. Massively parallel magnetohydrodynamic simulations show the turbulent plasma halo radiatively cools via a top-down multiphase condensation rain of warm filaments and molecular clouds. The multiphase precipitation inherits the hot halo kinematics and thermodynamics, ultimately establishing a 'cosmic weather'. In the nuclear region, the recurrent collisions between the clouds and filaments promote angular momentum cancellation and boost the SMBH accretion rate through a mechanism known as Chaotic Cold Accretion (CCA). The CCA rapid variability triggers powerful AGN outflows, which quench the macro cooling flow and star formation, while preserving the atmospheres of galaxies, groups, and clusters in global thermal equilibrium throughout cosmic time. I highlight the key imprints of AGN feedback and feeding, such as bubbles, shocks, turbulence, and condensed structures, with a critical eye toward observational concordance, including the X-ray plasma, optical filaments, and radio molecular clouds.
Only talks with videos
ESO Cosmic Duologues
Hypatia Colloquium
Informal Discussion
KES: Knowledge Exchange Series
Lunch Talk
Partly with videos