Seminars and Colloquia at ESO Garching and on the campus

December 2015

10/12/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Quasars, Mergers, and Velocity Dispersions
Gabriela Canalizo (University of California, Riverside)
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Abstract

Although mergers and starbursts are often invoked in the discussion of quasar activity and its effect on galaxy evolution, several studies have questioned their importance or even their presence in quasar host galaxies.   In this talk, I will discuss results from a long campaign of space- and ground-based imaging and spectroscopic observations of z < 0.5 QSO hosts that imply that mergers are indeed essential for the triggering of QSO activity, and that these mergers invariably induce starbursts either during and/or shortly after the merger.  In particular, I will discuss observations of a sample of host galaxies previously classified as passively evolving ellipticals.  Our results clearly show that these galaxies have undergone major episodes of star formation in the past ~2 Gyr. The morphologies of the host galaxies suggest that these aging starbursts were induced during the early stages of the mergers that resulted in the elliptical-shaped galaxies that we observe today.  The current AGN activity likely corresponds to the late episodes of accretion predicted by numerical simulations, which occur near the end of the mergers, whereas earlier episodes may be more difficult to observe due to obscuration. I will discuss numerical simulations that indicate that any potential current star formation or young stellar populations in these hosts would be confined to the central few kiloparsecs, a region that is typically outshined by the bright nucleus.  I will also discuss our efforts to search for these starbursts in type-2 QSOs.  Finally, I will discuss our ongoing work to probe the co-evolution of black holes and their hosts through scaling relations as a function of time.

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03/12/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Dark Matter and the Axion
Georg Raffelt (MPI Physics, Munich)
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Abstract

The physical nature of the cosmic dark matter remains elusive, but
several well-motivated extension of the particle-physics standard
model provide candidates that are experimentally searched. The
axion, a hypothetical very low-mass boson motivated by quantum
chromodynamics (QCD), will be introduced and ongoing experimental
searches as well as astrophysical limits will be reviewed. The
interest in axion dark matter has recently surged and a number of
completely new search initiatives have emerged.

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November 2015

12/11/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — 51 Peg, 20 years later, elusive Earth twin
Didier Queloz (University of Cambridge, UK)
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05/11/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The Wonderful Lives of Massive Stars until their Final Explosions and Beyond
Selma de Mink (University of Amsterdam)
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Abstract

Massive stars are rare and short-lived. Nevertheless, through their extreme
brightness, strong outflows and powerful explosions, they heat and stir
their surroundings, drive outflows on galactic scales, are thought to be
responsible for reionization and the main production the heavy elements in
the Universe. Because of their large impact, evolutionary models of massive
stars are an essential ingredient for a wide variety of astrophysical
problems. Recently it has become clear that the majority of massive stars,
possibly as much as 7 out of 10, will experience severe interaction with a
binary companion. I will discuss several aspects of our quickly increasing
understanding of how this affects (1) the lives of massive stars, (2) our
interpretations of observations of young stellar populations nearby and at
high redshift and transient phenomena and (3) our understanding of the role
that massive stars play through their radiative, mechanical and chemical
feedback.

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October 2015

08/10/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Tori, disks, and winds - the AGN dust emission at high angular resolution
Sebastian Hoenig (University of Southampton)
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Abstract

Mass accretion onto supermassive black holes occurs on scales beyond the diffraction limit of any single optical/infrared (IR) telescope. Thanks to the resolution power of the VLT Interferometer, we are now tapping into the outer accretion structure of active galactic nuclei (AGN) - commonly referred to as the "dusty torus". Several surprising results are challenging our current paradigm: While the bulk of the mid-IR emission originates from perpendicular where models would put the torus, the IR emission as a whole appears to be made of two components. In this talk I will give a basic introduction to IR interferometry and discuss what our recent results tell us about AGN unification and the physical processes that regulate accretion and feedback. I will also give a brief glimpse into how IR interferometry can help us establishing AGN as cosmological distance measures.

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01/10/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The Chemistry of Planet Formation: ALMA observations and laboratory simulations of protoplanetary disk volatiles
Karin Oeberg (Harvard-Smithsonian Center for Astrophysics)
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Abstract

During the past decade, the number of known planets has increased explosively, revealing an extreme range in planet compositions. The origin of this diversity is largely unknown. It is also unknown how common access to surface water and organics is on these planets, and thus the frequency of chemically habitable planets. I will present on how these questions can be addressed through a combination of astrophysical observations and laboratory simulations of the chemistry present in protoplanetary disks, the birthplaces of planets. We use spatially and spectrally resolved observations (ALMA and SMA) to explore the organic inventory, isotopic fractionation chemistry, and other chemical structures in disks. In parallel, we use laboratory ice experiment to quantify how these observed gas phase abundances relate to the total volatile reservoirs in disks, which are typically dominated by icy grain mantles. Recent highlights include observations of spectacular chemical ring structures that trace condensation-, temperature- and radiation-regulated chemistry, new constraints on isotopic fractionation during planet formation, and the detection of the first complex molecule in a disk. I will discuss these observations in light of laboratory constraints on ice chemistry, and how they compare with the chemical compositions found at earlier stages of star formation and in the Solar System.

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July 2015

03/07/15 (Friday)
10:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lecture series: Presupernova evolution, explosion and nucleosynthesis of massive stars
Lecture — Lecture 4
Prof. Marco Limongi (Rome Astronomical Observatory)
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Abstract

The series of lectures will focus mainly on the evolution, explosion and nucleosynthesis
of massive stars. The course will cover a variety of aspects related to the topic, starting
from the basic concepts of stellar evolution and nucleosynthesis to presupernova evolution,
supernova explosions and PopIII core-collapse supernovae. The course is mostly intended
for PhD students and post-doctoral researchers, or for whomever would like to brush-up
his/her knowledge on these topics.

The tentative breakdown of the lectures is as follows:

Lecture 1 - Tuesday, 30 June:
Introduction
Stellar Structure Basics
Thermonuclear reactions
Hydrostatic Nuclear Burning Stages

Lecture 2 - Wednesday, 1 July:
Presupernova Evolution of Massive Stars
Role of Mass Loss
Role of metallicity
Role of rotation

Lecture 3 - Thursday, 2 July:
Explosive Nucleosynthesis
Hydrostatic and Explosive Yields

Lecture 4 - Friday, 3 July:
Presupernova evolution and explosion of zero metallicity massive stars
Comparison with observations

Video

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02/07/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Decoding black hole variability
Phil Uttley (University of Amsterdam)
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Abstract

Variability from black holes - both stellar mass and supermassive - has been studied for many years, but we have only recently pieced together the physical origin of the variability. Developments in multiwavelength monitoring and X-ray spectral-timing now allow us to study the causal relationship between variations of different spectral components, allowing a direct link to the physics of the emitting regions close to the black hole.  I will describe the recent advances in this area which reveal some surprises about the role of the turbulent accretion disc in producing the variability, give clues to the nature of the mysterious quasi-periodic oscillations and show the promise of new X-ray spectral timing techniques to map the emitting regions closest to the event horizon.

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10:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lecture series: Presupernova evolution, explosion and nucleosynthesis of massive stars
Lecture — Lecture 3
Prof. Marco Limongi (Rome Astronomical Observatory)
Download video |

Abstract

The series of lectures will focus mainly on the evolution, explosion and nucleosynthesis
of massive stars. The course will cover a variety of aspects related to the topic, starting
from the basic concepts of stellar evolution and nucleosynthesis to presupernova evolution,
supernova explosions and PopIII core-collapse supernovae. The course is mostly intended
for PhD students and post-doctoral researchers, or for whomever would like to brush-up
his/her knowledge on these topics.

The tentative breakdown of the lectures is as follows:

Lecture 1 - Tuesday, 30 June:
Introduction
Stellar Structure Basics
Thermonuclear reactions
Hydrostatic Nuclear Burning Stages

Lecture 2 - Wednesday, 1 July:
Presupernova Evolution of Massive Stars
Role of Mass Loss
Role of metallicity
Role of rotation

Lecture 3 - Thursday, 2 July:
Explosive Nucleosynthesis
Hydrostatic and Explosive Yields

Lecture 4 - Friday, 3 July:
Presupernova evolution and explosion of zero metallicity massive stars
Comparison with observations

Video

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01/07/15 (Wednesday)
10:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lecture series: Presupernova evolution, explosion and nucleosynthesis of massive stars
Lecture — Lecture 2
Prof. Marco Limongi (Rome Astronomical Observatory)
Download video |

Abstract

The series of lectures will focus mainly on the evolution, explosion and nucleosynthesis
of massive stars. The course will cover a variety of aspects related to the topic, starting
from the basic concepts of stellar evolution and nucleosynthesis to presupernova evolution,
supernova explosions and PopIII core-collapse supernovae. The course is mostly intended
for PhD students and post-doctoral researchers, or for whomever would like to brush-up
his/her knowledge on these topics.

The tentative breakdown of the lectures is as follows:

Lecture 1 - Tuesday, 30 June:
Introduction
Stellar Structure Basics
Thermonuclear reactions
Hydrostatic Nuclear Burning Stages

Lecture 2 - Wednesday, 1 July:
Presupernova Evolution of Massive Stars
Role of Mass Loss
Role of metallicity
Role of rotation

Lecture 3 - Thursday, 2 July:
Explosive Nucleosynthesis
Hydrostatic and Explosive Yields

Lecture 4 - Friday, 3 July:
Presupernova evolution and explosion of zero metallicity massive stars
Comparison with observations

Video

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June 2015

30/06/15 (Tuesday)
10:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lecture series: Presupernova evolution, explosion and nucleosynthesis of massive stars
Lecture — Lecture 1
Prof. Marco Limongi (Rome Astronomical Observatory)
Download video |

Abstract

The series of lectures will focus mainly on the evolution, explosion and nucleosynthesis
of massive stars. The course will cover a variety of aspects related to the topic, starting
from the basic concepts of stellar evolution and nucleosynthesis to presupernova evolution,
supernova explosions and PopIII core-collapse supernovae. The course is mostly intended
for PhD students and post-doctoral researchers, or for whomever would like to brush-up
his/her knowledge on these topics.

The tentative breakdown of the lectures is as follows:

Lecture 1 - Tuesday, 30 June:
Introduction
Stellar Structure Basics
Thermonuclear reactions
Hydrostatic Nuclear Burning Stages

Lecture 2 - Wednesday, 1 July:
Presupernova Evolution of Massive Stars
Role of Mass Loss
Role of metallicity
Role of rotation

Lecture 3 - Thursday, 2 July:
Explosive Nucleosynthesis
Hydrostatic and Explosive Yields

Lecture 4 - Friday, 3 July:
Presupernova evolution and explosion of zero metallicity massive stars
Comparison with observations

Video

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11/06/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Cosmology and Astrophysics with Galaxy Clusters
Daisuke Nagai (Yale University, currently at MPA)
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Abstract

Galaxy clusters are the largest and most recently formed cosmological objects in the universe, making them powerful laboratories for both cosmology and astrophysics. The current generation of multi-wavelength cluster surveys (including Planck, ROSAT and SDSS with follow-up observations by Chandra, HST and XMM-Newton space observatories) have dramatically increased the sample size and the image quality of observed galaxy clusters out to high-redshift. However, the statistical power of these surveys are limited by complex and still poorly understood cluster astrophysics that shape their observable properties and evolution. In this talk, I will review recent advances and challenges in our understanding of cluster astrophysics and discuss future prospect for the use of galaxy clusters as a cosmological probe.

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May 2015

28/05/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — A new look at the Magellanic Clouds with the VMC survey
Maria-Rosa Cioni (University of Potsdam / AIP Potsdam)
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Abstract

The Magellanic Clouds illustrate an early-phase of a minor merger event. In spite of their importance in supplementing material to the Milky Way halo and the numerous investigations made in the last decade, there remain several uncertainties. Their origin is still a matter of debate, their satellite status is unclear, their mass is uncertain, their gravitational centres are undefined, their structure depends strongly on stellar populations and is severely shaped by interactions, their orbital history is only vaguely associated to star forming events and their chemical history rests upon limited data.
In this presentation I am going to discuss the advances provided by a comprehensive analysis of the stellar content of the galaxies. I am going to focus on the most recent results obtained from the VISTA survey of the Magellanic Clouds system (VMC) on the star formation history, structure, and proper motion and I am going to outline the possibilities offered by new observations with Gaia and wide-field spectrographs.

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21/05/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Systematic Properties of Galactic Winds: Implications for Models of Galaxy Evolution
Timothy Heckman (JHU Baltimore)
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Abstract

Galactic winds are the most dramatic form of feedback provided by massive stars. In the first part of my talk I will summarize the importance of galactic winds for the evolution of galaxies and the inter-galactic medium. I will briefly describe the physical processes that drive these winds, and give a short guided tour of the multi-phase wind driven from the local starburst galaxy M82. I will then describe how the properties of winds are typically incorporated in cosmological simulations and semi-analytic models. In the second part of my talk I report on recent work that has determined the dependence of the basic wind properties (outflow velocities, mass and momentum outflow rates) on the properties of the galaxy/starburst. These results are strongly at odds with some of the most popular wind prescriptions in simulations and models. In the third part of the talk I will describe observations of the impact of galactic winds on the circum-galactic medium. Finally, I will report on new observations that reveal how stellar feedback, including galactic winds, enabled early star-forming galaxies to re-ionize the universe.

Video

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April 2015

30/04/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The history of star formation, obscured by dust and revealed by Herschel
Seb Oliver (Sussex, U.K.)
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Abstract

One of the primary motivations for Herschel was to explore star
formation in the distant Universe.  To address this topic Herschel
invested significant fraction of its time in undertaking surveys
including the multi-tiered extragalactic survey, HerMES.  HerMES
mapped around 400 sq. degrees in the best studied extragalactic fields
on the sky and has uncovered 100s of thousands of distant star
forming galaxies.  In this talk I will review some of the key results
from HerMES.  In particular the Herschel maps reveal most of the
cosmic infrared background and these and other basic statistical
measurements have constrained our view on galaxy evolution models. I
will summarise what we have learned about the cosmic history of star
formation.  I will show how clustering measurements have been used to
reason that these distant star forming galaxies are the progenitors
of present day, massive galaxy, descendants.  I will show how Herschel
has revealed new insights into the relation between star formation and
central supermassive +black hole accretion activity.  Finally I'll
illustrate how Herschel is uncovering starburst galaxies when the
Universe was less than a billion years old.

Video

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23/04/15 (Thursday)
16:15, Auditorium Eridanus (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — High-Mass Star Formation: From Galactic to Protostellar Scales
Henrik Beuther (MPIA, Heidelberg)
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Abstract

The formation of the most massive stars affects our Milky Way
as a whole but at the same time, many of the physical processes
take place on very small spatial scales. This talk will highlight
recent results in that field covering large-scale Milky Way structures
and the locations of the high-mass star formation sites within our
home galaxy, as well as the small-scale physical and chemical
processes at place to actually build and form these high-mass stars.

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March 2015

12/03/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Eccentric Compact Object Mergers
Frans Pretorius (Princeton University)
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Abstract

Binary compact object mergers are among the primary gravitational wave sources expected to be observed by the next generation of ground-based gravitational wave detectors. Mergers where one or both compact objects are neutron stars will further produce electromagnetic emission, and coincident observation of this together with gravitational wave emission could teach us much about the progenitor systems, test general relativity in the dynamical strong field regime, and help elucidate the nature of matter at nuclear density. I will discuss ongoing work modeling such mergers within the context of general relativity coupled to ideal hydrodynamics, focusing on black hole-neutron star and binary neutron star systems merging with sizable eccentricity.  Large eccentricity is expected for mergers that occur following dynamical capture or 3-body interactions in dense cluster environments, and though they may be rarer than the traditional quasi-circular inspiral, they could exhibit strikingly different behavior, including zoom-whirl orbital dynamics and large amounts of unbound material for cases where the neutron star is tidally disrupted.

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05/03/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Very Low Mass Stars, Brown Dwarfs and Gas Giant Exoplanets
France Allard (Directrice de Recherche, CNRS)
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Abstract

Understanding the atmospheric and evolutive properties of Very Low Mass stars, brown dwarfs and gas giant exoplanets have been important challenges for modelers around the world since the discovery of the first brown dwarfs in the field (Nakajima et al. 1995) and in the Pleiades cluster (Rebolo et al. 1995).  Early studies have provided rich insights into atmospheric physics, with discoveries ranging from cloud formation (Tsuji et al. 1996), methane bands (Oppenheimer et al. 1995) and ammonia bands formation (Delorme et al. 2008), to the formation of quasi-molecular KI-H2 absorption (Allard et al. 2007), and to disequilibrium chemistry (Yelle & Griffith 2001).  New classical 1D models yield spectral energy distribution  (SED) that match relatively well that of M dwarfs, brown dwarfs and young gas giant exoplanets despite these complexities. These models have for instance explained the spectral transition from M to L, T and now Y brown dwarf spectral types (Allard et al. 2013).  However, in presence of surface inhomogeneities as revealed recently for a nearby brown dwarf (Crossfield et al. 2014), the SED may well fit exactly, but the model parameters could be far from exact, e.g. with the effective temperature by several hundred kelvins too cool in the case of dusty brown dwarfs and young gas giant exoplanets!

On the contrary, recent developments (revises more complete molecular opacities, revised solar abundances, calibration of the mixing length) have led the to a spectacular improvement of M Dwarfs model atmospheres and synthetic spectra, and therefore to a better knowledge of the Teff-scale of M Dwarfs (Rajpurohit et al. 2013) which has recently been confirmed by the study of 160 M dwarfs (Mann et al. 2015)!    This is promising at a time where planets are being searched around M dwarfs.  New evolution models for M Dwarfs have therefore been recently published (Baraffe et al. 2015).

I will review the progress achieved in reproducing the spectral properties of very low mass stars, brown dwarfs/gas giant exoplanets, and review progress in modeling more accurately their atmospheres using Radiation HydroDynamical (RHD) simulations.

Video

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February 2015

19/02/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Towards using Local Group dwarf galaxies as a cosmological probe
Nicolas Martin (University of Strasbourg)
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Abstract

The salience of satellite dwarf galaxies for understanding galaxy formation in a cosmological context has been made all the more evident in the past decade with the discovery of numerous faint Local Group galaxies. These faint systems are not only important to understand the faint end of galaxy formation but also their distribution around their host can test the hierarchical formation induced by the favored cosmological paradigm. I will review our successful effort to mine the two most ambitious surveys of the surroundings of the Milky Way and Andromeda galaxies, Pan-STARRS1 and PAndAS, for numerous new dwarf galaxies, before presenting the updated tally of MW/M31 satellites and what they are starting to tell us about galaxy formation in a LCDM universe.

Video

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12/02/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — What's the universe made of? Insights from strong lensing
Tommaso Treu (UCLA Physics & Astronomy, Los Angeles)
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Abstract

What is the nature of dark energy and dark matter? I will describe two
astronomical observations based on strong gravitational lensing that
can address this question in a novel way. In the first part of talk, I
use as cosmic "standard rods" strong gravitational lenses where the
background source is variable in time and the foreground deflector is
a massive galaxy. I will illustrate recent advances in modelling
techniques and data quality that enable a 6-7% measurement of absolute
distance from a single gravitational lens. I will show that results
from just two systems yield constraints on the equation of state of
dark energy and flatness comparable to those obtained with the best
probes.  In the second part of the talk I will discuss the use of
strongly lensed galaxies and quasars to detect the presence of dark
subhalos independent of their stellar content. This observation tests
a fundamental prediction of the cold dark matter model, i.e. that
galaxies should be surrounded by large numbers of dark satellite
subhalos. Proof that such satellites do not exist would force a
revision of the model in favor of more exotic alternatives like warm
dark matter.  I will then conclude by discussing the bright prospects
of studies of the dark sector using strong gravitational lensing.

Video

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05/02/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The baryon cycle: accretion, outflow and the circum-galactic medium
Celine Peroux (Laboratoire d'Astrophysique de Marseille)
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Abstract

A picture arises where galaxy formation is fed by inflows of gas from
the inter-galactic medium (IGM), counteracted by strong galactic
winds, which in concert establish the growth rate of gas and stars
within galaxies at all cosmic epochs. These processes can be
collectively described as a “baryon cycle". I will present results on
UVES observations of the neutral gas reservoir for star formation, the
kinematics of gas around galaxies probed with IFU SINFONI and
X-Shooter and prospects to detect the circumgalactic medium (CGM) in
emission with purpose-built facilities. I will finally cover future
prospects in this field with the forthcoming Extremely Large optical
Telescopes.

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January 2015

22/01/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — Unveiling evolutionary links among isolated, magnetized neutron stars
Rosalba Perna (Stony Brook University)
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Abstract

The magnetic field strength at birth has long been considered a fundamental property in determining the evolutionary path of a neutron star (NS). Objects with very high fields, collectively known as magnetars, are characterized by high X-ray quiescent luminosities, outbursts, and, for some of them, sporadic giant flares. While the magnetic field strength is believed to drive their collective behaviour, however, the diversity of their properties, and the observation of magnetar-like bursts from 'low-field' pulsars, has been a theoretical puzzle. In this talk, I will discuss results of long-term MHD simulations which, by following the evolution of magnetic stresses with in the NS crust, have allowed to relate the observed magnetar phenomenology to the physical properties of the NSs, and in particular to their age and magnetic field strength and topology. The dichotomy of 'high-B' field pulsars versus magnetars is naturally explained, and occasional outbursts from old, low B-field NSs are predicted.

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15/01/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — First Stars, First Black Holes
Andrea Ferrara (Scuola Normale Superiore, Pisa, Italy)
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Abstract

The appearance of the first stars about 100 million years after the Big Bang marked the beginning of the Reionization Epoch, an extended process in which the cosmic gas was ionized by the UV photons from the existing luminous sources. Most likely, in addition to stars, black holes also formed during the same epoch as end-products of massive star evolution, from direct collapse of gas clouds, or by stellar merging in dense stellar clusters. These black holes represent the "seeds" out of which observed super-massive black holes powering the most distant quasars were built. I will review the properties of  first stars and black holes, their role for reionization, and the tight physical relationships between these two types of sources. I will put particular emphasis on the critical current and future experiments that could allow us to understand in detail these initial phases of cosmic structure formation.

Video

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08/01/15 (Thursday)
16:15, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Munich Joint Astronomy Colloquium
Talk — The detailed history of nearby galaxies: messages from the deepest color-magnitude diagrams
Carme Gallart (Instituto de Astrofísica de Canarias)
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Abstract

Deep color-magnitude diagrams reaching the oldest main
sequence turnoffs offer the possibility to derive reliable, precise
star formation histories, and even, chemical enrichment histories for
the galaxies in our Local Group. I will discuss  these results for a
variety or Local Group galaxies, as well as their implications in a
number of astrophysics topics such as i) the early conditions of the
Universe: reionization and feedback; ii) the dwarf galaxy
classification and the origin of the different dwarf galaxy types;
iii) the effects in interactions in the evolution of the galaxies.

Video

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