Seminars and Colloquia at ESO Garching and on the campus

December 2016

15/12/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Mixing in stars in the era of high-performance computing
Pascale Garaud (UC Santa Cruz)
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Abstract

Mixing in the radiative zones of stars is one of the least well understood components of stellar evolution, and yet can, in many instances, play a crucial role. In recent years, however, much progress has been made in quantifying mixing by a variety of hydrodynamic instabilities, thanks to numerical experiments that have strongly benefited from advances in supercomputing. I will review the state of the field, and present perspectives on what can and should be done next by the stellar evolution community, and by the astrophysical fluid dynamics community.

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08/12/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Physical processes setting the multiphase structure of the interstellar medium
Thorsten Naab (MPA)
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Abstract

The interstellar medium (ISM) of galaxies drives galaxy evolution. However, it???s multi-phase structure is typically unresolved in cosmological galaxy formation simulations. I present recent progress on high-resolution numerical simulations (the SILCC project) investigating the differential impact of major physical processes setting the chemical and thermal multi-phase structure of the ISM including OB stellar winds, radiation and supernova explosions. We find evidence that stellar winds and radiation from massive stars primarily regulate star formation, while supernova explosions set the properties of the outflow driving hot gas. I also discuss the potential impact of non-thermal ISM components - magnetic fields and cosmic rays - on galactic outflows. With these simulations we also make first attempts towards more accurate predictions of important emission lines which are a major observables for galaxy formations studies at all cosmic epochs.

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01/12/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Outflows in X-ray binaries
Maria Diaz Trigo (ESO)
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Abstract

Accretion onto neutron stars and black holes powers the most luminous phenomena in the Universe. Associated to it is the existence of outflows, in the form of uncollimated winds or highly collimated relativistic jets. The origin of outflows and their feedback to the environment is one of the most debated topics in astrophysics today. In this talk I will review the current understanding of winds in X-ray binaries, their launching mechanism and their relation to specific accretion states. I will also discuss the potential interplay between the appearance/disappearance of winds and jets and the insight gained with ongoing observational programmes focused on the variability of such phenomena.

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November 2016

24/11/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The many flavours of star cluster dynamics
Michela Mapelli (INAF - Astronomical Observatory, Padova)
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Abstract

Most star clusters are collisional systems, i.e. their two-body relaxation timescale is shorter than their lifetime. This simple fact has strong implications: intense dynamical processes occur during the entire evolution of a star cluster, shaping both its structural properties and its stellar content. Mass segregation and Spitzer instability imprint their features already in the early stages of star cluster evolution, leading to repeated collisions of massive stars. This process might lead to the formation of very massive stars (>150 Msun) and even intermediate-mass black holes (IMBHs, 100-1000 Msun), depending on star cluster metallicity. Moreover, binary systems undergo frequent three-body encounters and even dynamical exchanges, which lead to dynamical ejections and/or the formation of more and more massive binaries. These aspects are crucial for the demography of massive double black hole binaries, which are important sources of gravitational waves for both ground-based and space-borne detectors. Finally, one of the most important (but less studied) ingredients of star cluster dynamics is the role of gas during star cluster formation. I show that torques in the parent molecular cloud imprint a substantial amount of rotation to embedded star clusters, potentially affecting their further evolution.

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17/11/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The formation of massive black-hole binaries: Understanding the Advanced LIGO detections
Philipp Podsiadlowski (University of Oxford)
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Abstract

The Advanced LIGO (aLIGO) gravitational-wave detector this year reported the discovery of the first direct detection of gravitational waves confirming Einstein's Theory of General Relativity in its extreme limit. All sources of these gravitational waves detected so far were caused by the merging of two massive stellar-mass black holes. In this talk I will first summarize the main aLIGO results and then discuss in detail the three main channels that have been proposed to explain their origin, involving (1) dynamical formation, (2) common-envelope evolution, and (3) chemical homogeneous evolution (CHE), and how it may be possible to distinguish among these models. I will then focus on the CHE formation model, showing recent results from our own work, including cosmological simulations and their implications for the future detection of intermediate-mass black-hole mergers, gamma-ray bursts, pair-instability supernovae and neutron-star/black-hole mergers. The model also has application to ultra-luminous X-ray sources, in particular the most luminous ones.

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10/11/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Supernova Traces in the Deep-Sea and their link to the Local Bubble
Jenny Feige (TU Berlin, Zentrum für Astronomie und Astrophysik)
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Abstract

A 2-3 million year old 60Fe-signal was detected in Pacific deep-sea
geological archives and in lunar samples. This long-lived isotope is not
produced on Earth, however, it is generated in massive stars and ejected
during supernova explosions. We have found that this signal is extended
in time and is present in marine reservoirs around the globe. A second
6.5-8.7 Myr old signature was revealed in a manganese crust. The recent
injection of 60Fe into the solar system coincides with the formation of
the Local Bubble, a large cavity in the interstellar medium produced by
multiple supernovae, which surrounds our solar system. The most likely
sources are stellar explosions within a moving group that passed the
solar vicinity, and whose surviving members are now in the
Scorpius-Centaurus stellar association. With analytical and numerical
models generating the Local Bubble, we explain the younger
60Fe-signature and link the recent evolution of the solar neighborhood
to the terrestrial anomalies.

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October 2016

27/10/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Large-scale structure cosmology using hydrodynamical simulations
Ian McCarthy (Liverpool John Moores University)
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Abstract

ESA's Planck mission has recently delivered on its promise to obtain ~few percent level constraints on the fundamental parameters of the standard model of cosmology, the LambdaCDM model. In spite of commonly-made claims that "all is well", detailed comparisons to other datasets are beginning to reveal some interesting tensions. Some measurements of local large-scale structure (LSS) in particular appear at odds with the CMB results. A few recent studies have proposed massive neutrinos as a way to reconcile the CMB and LSS measurements. However, before arriving at such a strong conclusion (or adopting any other modification of the standard model) we must be certain that we have properly dealt with all important sources of systematic error. Precisely modelling large-scale structure is challenging in particular, due to the non-negligible effects of feedback processes associated with galaxy formation. Here I present the first results from a new large hydrodynamical simulation campaign (BAHAMAS - BAryons and HAloes of MAssive Systems) designed specifically for LSS cosmology purposes and that realistically captures the effects of feedback on LSS. A number of the simulations include a massive neutrino component. Using virtual observations of the simulations, I re-assess the evidence for tensions between the CMB and various LSS probes, including cosmic shear, CMB lensing, galaxy clustering, the Sunyaev-Zel'dovich effect and so on. I then show the effects of massive neutrinos on these various LSS tests and discuss the current evidence for and against their cosmological importance.

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20/10/16 (Thursday)
15:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — News from the dark universe: The discovery of gravitational waves
Hartmut Grote (MPI for Gravitational Physics, Hannover)
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Abstract

In 1916, Albert Einstein predicted the existence of gravitational waves but considered them to be too weak to be ever detected. Nonetheless, 100 years after their prediction, and after 50 years of effort, scientists and engineers have succeeded in this challenge, building multi-kilometer laser interferometers capable of measuring length changes close to the Heisenberg uncertainty limit. The first detections of gravitational waves allow us to listen to the ripples of space-time and witness the merging of black holes more than a billion years ago. Gravitational-wave astronomy has started and, together with electromagnetic and neutrino observations, is expected to shed new light on energetic astrophysical events.

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13/10/16 (Thursday)
15:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Accretion on disparate scales: molecular clouds to protoplanetary discs
Patrick Hennebelle
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Abstract

While primordial universe was extremely uniform, it is now deeply structured with huge density contrasts from galaxy clusters to planets. This implies that intense episodes of accretion are taken place recursively at all spatial scales. How does it exactly happen and what role are these accretion events playing ? During the talk I will focus on three particular types of objects, namely the molecular clouds, the proto-stellar clusters and the late proto-planetary discs. For each of these three cases, I will describe how accretion proceeds and how it contributes, together with other physical processes, to drive the evolution of the system.

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June 2016

30/06/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Galaxy Evolution in 3D
Lisa Kewley (RSAA/Australian National University)
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Abstract

Throughout the history of the universe, shocks and 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. For local galaxies, we use multi-object integral field spectroscopy to build the largest sample of galaxies with wide 3-dimensional imaging spectroscopy. We combine these results with insights into the early universe probed through gravitational lensing and near-infrared integral field spectroscopy. 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, and active galactic nuclei in galaxies as a function of environment and redshift. I will finish by discussing how this field will be transformed with JWST and in the ELT era.

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23/06/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The Illustris simulation and beyond
Mark Vogelsberger (MIT, Cambridge)
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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.

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May 2016

12/05/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Cosmic Web Imager Observations of Circum-Galactic and Circum-QSO Medium Emission at High Redshift
Chris Martin (Caltech)
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Abstract

I will describe recent results from the Palomar Cosmic Web Imager (PCWI). These include the discovery of filamentary Lyman alpha emission and a giant (>120 kpc) protogalactic disk around a QSO, filamentary emission and a large gas proto-disk with possible spiral inflow near a second QSO, and filamentary emission around and kinematics in a Lyman Alpha Blob consistent with a large rotating gas disk. The discovery of filamentary and disk-like structures is evidence for cold accretion inflows with significant angular momentum. I will also describe future instrumentation exploring IGM emission on the ground and in space.

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April 2016

21/04/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The Collisionless Dynamics of Dark Matter
Oliver Hahn (Observatoire de la Cote d'Azur)
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Abstract

The dynamics of dark matter provides the backbone of studies of cosmic structure formation. Despite our ignorance about the particle physics nature of the elusive dark matter, its microscopic properties leave a distinct imprint on its macroscopic dynamics which can be studied in computer simulations. Such N-body simulations have driven most of our theoretical knowledge about the distribution of matter in the Universe which in turn reflects properties of the dark matter particle. I will review the theoretical assumptions underlying such simulations and how they are used to study the nature of dark matter through its dynamics. I will particularly focus on recent attempts to model dark matter in the continuum limit. I will demonstrate how such new methods can be used to overcome known problems of N-body simulations, but also help to gain completely new insights into dark matter dynamics. Finally, I will report on recent results on the formation and evolution of the very first haloes in cold dark matter cosmologies.

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07/04/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Planet formation and evolution: origin of the diversity of planetary systems
Alessandro Morbidelli (Observatoire de la Cote d'Azur)
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Abstract

The discovery of extrasolar planets has revealed an unexpected diversity among planetary systems.
Our Solar System appears to be a "minority case", given that about 75% of the stars seem to have planets with characteristics that are absent in our own system.
Understanding the origin of such a diversity is a major goal in planet formation and evolution models.

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March 2016

31/03/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Rotation, Magnetic Activity, and Mass Loss of Sun-Like Stars
Sean Matt (University of Exeter)
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Abstract

An enormous amount of what we know about the universe and our own place on Earth depends on our understanding of stars. Yet, even for the most familiar stars, there are still major unsolved questions related to rotation, magnetic activity, and mass loss. I will discuss an emerging self-consistent picture that links all of these processes together and to the overall evolution of Sun-like and low-mass stars. This progress is due to large and diverse new datasets, advances in physical models for the loss of angular momentum (which itself depends upon magnetism and mass loss), and the incorporation of these models into long-term stellar evolution calculations.

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10/03/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — A detailed X-ray view of the intracluster medium
Jeremy Sanders (MPE)
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Abstract

Using new very deep Chandra and XMM-Newton X-ray observations of nearby galaxy clusters we are obtaining an unprecedented view of the intracluster medium in the cores of these objects. Rather than purely symmetric hydrostatic atmospheres, we see dynamic places where multiple physical processes are important, including AGN feedback, gas sloshing, mergers, sound waves, turbulence, enrichment and plasma instabilities. I will review some interesting results from the launch of these satellites and show some recent results from deep observations of the Centaurus, Coma and Perseus galaxy clusters.

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February 2016

04/02/16 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The wild youth of galaxy clusters
Emanuele Daddi (CEA Saclay, France)
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Abstract

I will present recent efforts to understand early cluster formation phases in the distant Universe, when the first giant dark matter halos were growing, and baryons falling into their deep potential wells took part to prodigiously vigorous activity of galaxy and black hole assembly. These phases are expected to be crucial to understand the processes leading to the formation of dominant elliptical population and well relaxed hot gas atmospheres, as observed in local massive galaxy clusters. New observations with ALMA, NOEMA, Herschel, HST and Keck of two dense structures at z=2 and 2.5 provide new insights into these problematics. Euclid, Athena, ALMA, SKA, JWST, Keck CWI (a bluer MUSE!), and the ELT(s) hold the promise to revolutionise this field in the coming decades.

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