Seminars and Colloquia at ESO Santiago

December 2013

04/12/13 (Wednesday)
15:30, Urania room (ESO, Santiago) | ESO Santiago
ESO Colloquium
Talk — Massive stars as Cosmic Engines: from the chemical evolution of galaxies to the birth of the solar system
Georges Meynet (University of Geneva)

Abstract

I shall begin by reviewing some puzzling facts about the nucleosynthesis having occurred in the early phases of the life of our own Galaxy and show how the current models face some difficulties in accounting for them. Some possible solutions for overcoming these difficulties will be presented as well as some future observational tests allowing to decide whether these solutions might be valid or not. More precisely we shall address the questions of the origin of the nitrogen and of neutron capture elements in very metal poor stars, as well as the question of the formation of the Carbon Enhanced Metal Poor stars. We shall also discuss the intriguing results indicating the presence of multi populations in globular clusters. In a second part, we shall discuss how isotopic anomalies observed in meteorites can reveal the stellar environment in which our solar system was born 4.57 billion years ago.

November 2013

29/11/13 (Friday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — Terzan 5: the remnant of a pristine fragment of the Galactic Bulge?
Alessio Mucciarelli (University of Bologna)

Abstract

Terzan 5 is a stellar system commonly catalogued as a globular cluster (GC), located in the inner Bulge of our Galaxy. Two distinct sub- populations have been recently discovered in this system (Ferraro et al. 2009).They define two well separated red clumps in the (K, J-K) color-magnitude diagram (CMD). Moreover, the stars of Terzan 5 cover a large (>0.5 dex) [Fe/H] range, without the typical anti- correlations observed in genuine GCs (Origlia et al. 2011, Massari et al. 2013). T hese observational results demonstrate that Terzan 5 is not a genuine GC, but a stellar system that experienced complex star formation and chemical enrichment histories. The strong chemical similarity with the Bulge, together with the location in the inner region of it, suggest that Terzan 5 is not the nucleus of an accreted dwarf galaxy, but possibly the relic of one of the pristine fragments that contributed to form the Bulge itself.

18/11/13 (Monday)
00:00, Santiago | ESO Santiago

Abstract

The study of the structure and morphology of galaxies is one of the major astronomical tools to address how galaxies form and evolve. There has been much recent progress in understanding the properties of different structural components in nearby and intermediate redshift (z ~ 1-2) galaxies. The strengths and limitations of the different techniques for obtaining structural measures of galaxies, particularly with regard to handling large surveys, will be highlighted. This conference will bring together over 100 observers and theorists, and it is intended to be highly participative, with substantial time devoted to discussions. More details can be found here.

12/11/13 (Tuesday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — A search for faint companions of the nearest stars with CanariCam and VHS
Bartek Gauza (IAC Spain)

Abstract

After two decades of discoveries, the census of substellar objects in the solar neighborhood  remains incomplete. Current imaging surveys carried out in the near and mid-infrared are expected to unveil numerous ultracool dwarfs and expand the population to previously undetectable temperature ranges. I will present a review of our searches for substellar companions around stars in the solar vicinity (d<10 pc). The searches are based on the southern near-infrared VISTA  Hemisphere Survey (VHS) combined with WISE and 2MASS catalogues and on a deep mid-IR imaging program carried out with CanariCam at the 10.4m GTC, in the Northern sky. We achieve sensitivity and resolving power that enables us to detect early Y dwarfs (Teff ~300-500K) at separations larger than 10 AU.

October 2013

22/10/13 (Tuesday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — Migrating stars: the true hitchhikers of the galaxy
Juan Carlos Muñoz Mateos (ESO)

Abstract

The spatial distribution of stars of different ages within galactic disks is often used to infer how galaxies were assembled through cosmic time. However, this requires assuming that stars have  always remained at roughly the same distance from the galactic center. Interestingly, though, recent theoretical and observational results suggest that stars can actually venture quite far from their initial birth radius. This raises a critical question: is the present-day radial distribution of old stars in disks determined mainly by in-situ star formation or by radial stellar migration? I will present our latest findings on this subject, based on the Spitzer Survey of Stellar Structure in Galaxies (S4G), a large survey of more than 2300 nearby galaxies imaged at 3.6 and 4.5 microns, down to depths below 1 Msun/pc2. We provide empirical evidence that resonant interactions with bars and spiral arms can rearrange old stars even at large radii. I will also discuss our current efforts to map the distribution of molecular gas in galaxies with potential signs of migration, in order to quantify how in-situ star formation and radial migration compete to build and mold the stellar backbone of galaxies.

16/10/13 (Wednesday)
15:30, Urania room (ESO, Santiago) | ESO Santiago
ESO Colloquium
Talk — A unifying view of AGN sub-pc scale structure> pushing the limit of infrared interferometry
Makoto Kishimoto (MPIfR)

Abstract

One of the big reasons why the progress in our understanding of the AGN mass accretion process has been very slow is the absolute lack of appropriate spatial resolutions. However, long-baseline interferometry in infrared wavelengths has been breaking the ground over the last several years. First I will review the recent findings in the interferometric studies of the innermost dusty structure in AGNs both in the near- and mid-infrared using the VLTI and Keck interferometer. Based on these studies, I will show that a unifying view of the sub-pc scale structure is now emerging, where the radiation pressure on dust grains is playing a central role in forming the structure. I will also discuss the up-to-date status of our on-going software effort to push the sensitivity limits of VLTI instruments.

08/10/13 (Tuesday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — GRBs in 2013: Progress and recent results
Thomas Krueler (ESO Chile)

Abstract

Long-duration gamma-ray bursts (GRBs) provide luminous beacons to distant sites of active star-formation across the universe. GRBs represent a particularly extreme form of massive stellar death, providing important insight into the nature of massive stars and the complex evolutionary processes that govern the end of their lives. Even more excitingly, because GRBs can be detected across the entire electromagnetic spectrum even out to very high redshifts, studies of these events and their environments provide one of the very few means of probing the high-redshift universe. I will review the recent progress of the field, with an emphasize on new results derived from sample studies and their implications for the nature of GRBs and their host galaxies.

07/10/13 (Monday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — Kinematics and chemical elements of the very metal poor Globular Cluster NGC 4372
Nikolay Kacharov (University of Heidelberg)

Abstract

NGC 4372 is a poorly studied, old, and very metal poor Globular Cluster (GC) located close to the Galactic disk and suffering from a severe differential reddening. It was likely dynamically stirred during its frequent crossings of the Galactic disk. Here, I will present the first ever high-resolution observations of it, taken with the FLAMES instrument at the VLT. Our sample consists of 131 unique red giant stars, confirmed cluster members. We found [Fe/H] = -2.2 ± 0.1 dex without any significant metallicity spread. We have also derived the abundances of several alpha, iron-peak and n-capture elements, as well as the p-capture element Sodium, which is crucial to assess the existence of multiple populations in this GC. I will focus on the kinematic properties of NGC 4372. Based on precise radial velocities and an analytic Plummer model, we have computed the central velocity dispersion σ0 = 4.7 ± 0.9 km/s and we also found a clear signal of systemic rotation with an amplitude v_rot = 2.0 ± 0.2 km/s. NGC 4372 has unusually high systemic rotation to velocity dispersion ratio for its metallicity, which puts it in line with other very metal poor GCs like M 15 and NGC 4590, and could bring some clues to the origin of those very low metallicity systems. Finally, we found a mild flattening of NGC 4372 in the direction of its rotation. This observation favours that the flattening is indeed caused by the systemic rotation rather than tidal interactions with the Galaxy.

03/10/13 (Thursday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — The VVV-SkZ Pipeline: How to get Automatic PSF-fitting phometry from VISTA surveys. Present status and future implementations
Francesco Mauro (Universidad de Concepción)

Abstract

The VVV-SkZ_pipeline is a DAOPHOT-based photometric pipeline, created to perform PSF-fitting  photometry of ``VISTA Variables in the Via Lactea'' (VVV) ESO Public Survey data. The pipeline replaces the user, avoiding repetitive interaction in all the operations, retaining all of the benefits of the power and accuracy of the DAOPHOT suite. The pipeline provides an astrometric photometric catalog reliable up to more than 2 magnitudes brighter than the saturation limit, where other techniques fail. It also produces deeper and more accurate photometry. These achievements allow the VVV-SkZ pipeline to produce data well anchored to the selected standard photometric system and analyze important phenomena (i.e. TRGB, RGB slope, HB morphology, RR Lyrae), that other methods are not able to manage.

September 2013

23/09/13 (Monday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — Multiple stellar systems
Petr Zasche (Charles University, Prague)

Abstract

The multiplicity fraction within the galactic (or extragalactic) stellar population still remains an open question. How many quadruples are there among the other binaries? What about the quintuples or even sextuple star systems? There are some methods how other bodies in eclipsing binary systems are being discovered. But are these methods adequately reliable?

12/09/13 (Thursday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — Studies on galaxy formation using high resolution deep imaging of high-z QSO fields
Yiping Wang (National Astronomical Observatories, Beijing, China)

Abstract

Studies on the high-z Lyman Limit absorbers, as well as the high redshift QSO host galaxies have received increasing attention within these years. Driven by the frontier sciences, techniques which would provide high spatial resolution for the study of the faint objects or materials in extremely close proximity to bright QSOs have been developed significantly during these decades. We will present here the primary results of our pilot study using ground-based 8m class telescope Subaru and its adaptive optics systems to detect the intervening galaxies close to the QSO sightlines, as well as our efforts to resolve and study the QSO host galaxies at high redshift.

11/09/13 (Wednesday)
15:30, Urania room (ESO, Santiago) | ESO Santiago
ESO Colloquium
Talk — Molecular hydrogen in the halo of a galaxy at z~0.56
Neil Crighton (MPIA)

Abstract

Measuring rest-frame ultraviolet rotational transitions from the Lyman and Werner bands in absorption against a bright background continuum is one of the few ways to directly measure molecular hydrogen (H2). In this talk I will discuss a new detection of H2 at z=0.56 in a sub-damped Lyman-alpha system, the first such system analysed at a redshift <1.5 beyond the Milky Way halo. Using spectra taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope, our group has shown that it has a surprisingly high molecular fraction: log f(H2) > -1.93 ± 0.36. This is higher than f(H2) values seen along sightlines with similar N(HI) through the Milky Way disk, the Magellanic clouds, or towards most higher redshift quasars. The metallicity of the absorber is ~0.14 solar. Absorption from associated low-ionisation metal transitions such as OI and FeII is observed in addition to OVI. Using theoretical models we show that there are three distinct gas phases present; a cold ~100 K phase giving rise to H2, a ~10^4 K phase where most of the low-ionisation metal absorption is produced; and a hotter phase associated with OVI. Based on similarities to high velocity clouds in the Milky Way halo showing H2 and the presence of two nearby galaxy candidates with impact parameters of ~10 kpc, we argue the absorber does not arise in an interstellar medium that is actively forming stars, but instead may be produced by a tidally-stripped structure similar to the Magellanic Stream.

09/09/13 (Monday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — Capabilities and scientific prospects of the VLTI-GRAVITY instrument
Pierre Kervella (Observatoire de Paris-Meudon)

Abstract

Capabilities and scientific prospects of the VLTI-GRAVITY instrument
P. Kervella, T. Paumard, G. Perrin, et al. The GRAVITY instrument is a general-purpose, second generation beam combiner for the VLTI currently being assembled at MPE Garching. The primary scientific driver of GRAVITY is the observation of Sgr A* at the Galactic Center, and its surroundings. GRAVITY will combine the light of four Auxiliary Telescopes or Unit Telescopes, and will be operated both in single field and dual field modes. It will provide spectroscopic dispersion up to R=4000 over the full K band, for objects as faint as mK=10 in single field, and up to mK=19 when a nearby reference with mK<=10 is available. Its astrometric accuracy in dual field mode will reach 10 microarcseconds between the two interferometric channels, up to a separation of 6" (with the Auxiliary Telescopes, 2" with the Unit Telescopes). The arrival of GRAVITY at Paranal is scheduled in late 2014, and its first observations are foreseen in early 2015. It is therefore timely for observers to start thinking about how GRAVITY can contribute to their research. Although the design of GRAVITY is driven by Sgr A* science, its unique capabilities promise innovative observations in many other scientific fields. I will present an overview of the how GRAVITY will contribute to the Galactic Center science, stellar physics and other fields in astrophysics.

09:30, Santiago | ESO Santiago
Workshop — Instrumental capabilities of ESO and JAO (ALMA)

Abstract

the Joint ALMA Observatory and ESO Vitacura are organizing a one-day workshop showcasing
the instrumental capabilities of ESO and JAO (ALMA) and their respective science highlights.
The objective, in time for the ESO deadline, is to provide information about what each instrument
can do for you, to complement your current research and provide an opportunity for greater scientific
exploration and collaboration. 
All scientists at ESO Garching are also invited to participate in this workshop by videocon from our Council room.
The workshop will take place in Vitacura from 9:30-17:00 Chilean time, which corresponds to 15:30-23:00 Garching time.

August 2013

27/08/13 (Tuesday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — Metallicities and alpha-enhancement of red giant stars in 51 Milky Way globular clusters: homogeneous scale and multiple populations
Bruno Dias (ESO, Chile)

Abstract

We are carrying out a survey of 51 poorly studied Milky Way globular clusters, by means of spectroscopy of ~20 red giants per cluster. Optical spectra (4600-5800 A) were obtained with the FORS2@VLT/ESO, at a resolution Delta lambda ~ 2.5 A. We use ETOILE code (Katz et al. 2011) to derive radial velocities, Teff, log g, [Fe/H] and [Mg/Fe] for each star, by finding the best fitting spectrum among a grid of observed or synthetic stars (MILES and Coelho et al. 2005). The main contributions of this work are: to provide a homogeneous scale of [Fe/H], [Mg/Fe], and radial velocities for the 51 clusters -- in particular for the 29 more distant and/or highly reddened ones -- to provide a catalogue of confirmed member stars for each cluster, in addition to find interesting cases for follow-up with high resolution data (like the massive clusters M 22, and NGC 5824, for which we found a spread in [Fe/H]).

21/08/13 (Wednesday)
16:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Colloquium
Paul Vreeswijk

Abstract

We present results from our on-going survey of GRB afterglows with the Ultra-violet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope. Our focus is on the variability of absorption lines from excited levels of singly ionized iron (FeII) and nickel (NiII), now observed in half a dozen of spectra. In most cases, the variability can be well described with a simple model in which afterglow UV photons are exciting a cloud of atoms at a hundred parsec to a kiloparsec away from the burst. This is much further out than the neutral gas was originally thought to be. UVES observations of GRB 080310 show the column densities of all detected levels of FeII to decrease in time, while the population of an excited level of doubly ionized iron, FeIII (^7S_3, the lower level of the UV34 triplet), never detected before in a GRB afterglow, is increasing in time. We demonstrate that a large fraction of the FeII ions are being ionized by GRB afterglow photons during the first hour after the GRB. We find that the main reason for detecting on-going ionization along the GRB 080310 sightline is not because the absorber is closer to the GRB than for the sightlines where only excitation is observed, but rather it is a combination of the very low HI column density and an overabundance of iron in the GRB 080310 absorbing gas.

20/08/13 (Tuesday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Talk — The mid-infrared properties of local active galactic nuclei at high-angular resolution
Daniel Asmus (MPIfR)

Abstract

Mid-infrared (MIR) observations of active galactic nuclei (AGN) enable the study of the astrophysical dust in these objects. This dust plays a key role regarding the central accreting supermassive black hole and the surrounding star formation. Only the high angular resolution (HAR) provided by 8-meter class telescopes allows us to isolate the emission of the central engine on scales of a few tens of parsecs. I present a sample of ~250 local AGN which comprises all ground-based HAR MIR observations performed to date. The photometry in multiple filters allows to characterize the properties of the dust emission for most objects. Because of its size and characteristics, this sample is very well-suited for AGN unification studies. In particular, I discuss the enlarged MIR--X-ray correlation which extends over six orders of magnitude in luminosity and potentially probes different physical mechanisms. Finally, tests for intrinsic differences between the AGN types are presented.

14/08/13 (Wednesday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Adriane Liermann (AIP)

Abstract

The Galactic center region is surprisingly rich in young stellar clusters, hosting a significant fraction of the Milky Way's population of high-mass stars (OB and Wolf-Rayet types). In combining photometric and spectroscopic surveys, the basic characteristics of the clusters' stellar populations have been successfully revealed, e.g. cluster membership via proper motion studies confirmed, and the spectroscopic determination of fundamental stellar parameters. I'll give an insight to observations and results obtained for the Arches and Quintuplet cluster, presenting Color-Magnitude diagrams as well as Hertzsprung-Russell diagrams. In comparison with stellar evolution models and isochrones we can estimate the evolutionary status of both stars and host cluster. This reveals a puzzling age discrepancy between the high-mass evolved stars and the main-sequence cluster members.

12/08/13 (Monday)
12:00, Urania room (ESO, Santiago) | ESO Santiago
ESO Thirty Minute Talks
Sebastian Comeron (University of Oulu)

Abstract

Thick discs are disc-like components with a scale height larger than that of the classical discs. They are most easily detected in close to edge-on galaxies in which they appear as a roughly exponential excess of light which appears a few thin disc scale heights above the midplane. Their origin has been considered mysterious until recently and several formation theories have been proposed. Unveiling the origin of thick discs is important for understanding galaxy evolutionary processes. I will review the results we obtained on thick discs using data from the S4G: 1) Thick discs are much more massive than previously thought. This advocates for an in situ origin of thick discs at high redshift and for them being a reservoir of missing baryons. 2) The superposition of thin and thick discs with different scale lengths is the reason of at least half of disc antitruncations.

April 2013

08/04/13 (Monday)
09:00, Santiago | ESO Santiago

Abstract

The meeting will cover topics related to the final stages of stellar evolution and the many important aspects of astronomy that depend on understanding how stars die and what happens to their remnants. Topics related to the stars themselves and how their later stages of evolution proceed, as well as how their demise affects their immediate surroundings and host galaxies, will be addressed. Details can be found here. The deadline for registration has elapsed.