ESO Santiago Science Colloquia and Seminars 2013

December 2013

2.12.13 (Monday)
12:00
"Finding small planetary signals in noisy data"
Damien SEGRANSAN (U Geneva)
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"Finding small planetary signals in noisy data"

Damien SEGRANSAN (U Geneva)

Abstract

The author will discuss the difficulty to search for small multiple planetary system in the HARPS data and a few pitfalls that could lead to false planet detections. He will illustrate his talk with the detection of Kepler-78 b that was made with HARPS-N at the TNG and show how they managed to beat the stellar noise.
3.12.13 (Tuesday)
12:00
"Observational tests of an inhomogeneous cosmology"
Christoph SAULDER (ESO, Chile)
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"Observational tests of an inhomogeneous cosmology"

Christoph SAULDER (ESO, Chile)

Abstract

One of the biggest mysteries in cosmology is Dark Energy, which is required to explain the accelerated expansion of the universe within the standard model. But maybe one can explain the observations without introducing new physics, by simply taking one step back and re-examining one of the basic concepts of cosmology, homogeneity. In standard cosmology, it is assumed that the universe is homogeneous, but this is not true at small scales (a few 100 Mpc). Since general relativity, which is the basis of modern cosmology, is a non-linear theory, one can expect some backreactions in the case of an inhomogeneous matter distribution. Estimates of the magnitude of these backreactions (feedback) range from insignificant to being perfectly able to explain the accelerated expansion of the universe. In the end, the only way to be sure is to test predictions of inhomogeneous cosmological theories, such as timescape cosmology, against observational data. If these theories provide a valid description of the universe, one expects aside other effects, that there is a dependence of the Hubble parameter on the line of sight matter distribution. The redshift of a galaxy, which is located at a certain distance, is expected to be smaller if the environment in the line of sight is mainly high density (clusters), rather than mainly low density environment (voids). Here we present a test for this prediction using redshifts and fundamental plane distances of elliptical galaxies obtained from SDSS DR8 data. In order to get solid statistics, which can handle the uncertainties in the distance estimate and the natural scatter due to peculiar motions, one has to systematically study a very large number of galaxies. Therefore, the SDSS forms a perfect basis for testing timescape cosmology and similar theories. The amazing preliminary results of this cosmological test are presented.
4.12.13 (Wednesday)
15:30
"Massive stars as Cosmic Engines: from the chemical evolution of galaxies to the birth of the solar system"
Georges MEYNET (U Geneva)
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"Massive stars as Cosmic Engines: from the chemical evolution of galaxies to the birth of the solar system"

Georges MEYNET (U 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.
12.12.13 (Thursday)
15:30
"Stellar Black Holes at the Dawn of the Universe"
Felix MIRABEL (CEA-Saclay, France & Conicet, Argentina)
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"Stellar Black Holes at the Dawn of the Universe"

Felix MIRABEL (CEA-Saclay, France & Conicet, Argentina)

Abstract

The re-ionization of the universe that took place during the first hundreds millions years is one of the major frontiers in cosmology. Until recently, most models of the re-ionization have considered the ultraviolet radiation from the first generations of massive stars as the only important factor in the process of re-ionization of the intergalactic medium. Based on recent results on the evolution of massive stars and high energy astrophysics, I propose that besides the UV radiation of the first generations of massive stars, feedback from their fossils, namely, X-rays and relativistic jets from stellar black holes, played an important role, determining the early thermal history of the universe and partially ionizing the intergalactic medium over large volumes of space. Feedback from accreting black holes had a direct impact on the properties of the faintest galaxies at high redshifts, the smallest dwarf galaxies in the local universe, and on the cold dark matter model of the universe.
18.12.13 (Wednesday)
15:30
"Bridging the links between absorption and emission-selected galaxies"
Pasquier NOTERDAEME (IAP)
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"Bridging the links between absorption and emission-selected galaxies"

Pasquier NOTERDAEME (IAP)

Abstract

In the past 15 years, efficient observational strategies have allowed to detect light from galaxies in the early Universe, each of them revealing a subset of the overall galaxy population. For example, Lyman-break galaxies (LBGs) mostly probe bright massive galaxies with strong stellar continuum, Lyman-alpha emitters (LAEs) probe somewhat lower mass systems with little dust, and IR and sub-mm observations reveal galaxies with high star-formation rate and dust content. On the other hand, the study of intervening absorption systems in the spectra of bright background sources such as quasars or GRB afterglows is a very powerful technique that allows to detect and study any amount of gas along the line of sight. In particular, damped Lyman-alpha systems (DLAs) are characterised by large neutral hydrogen column density and are hence thought to arise in or close to galaxies. Because their detection is independent of the associated galaxy, DLAs should probe the overall luminosity function. However, despite intensive efforts, the link between absorption and emission-selected galaxies remains obscure, mainly due to the paucity of direct detections. In this talk, I will present recent progress towards describing high-redshift galaxies and absorption systems in a single picture, with an emphasis on the detections of individual absorber's host galaxies made possible by powerful instrumentation on VLT as well as statistical detections using the SDSS-Baryon Oscillation Spectroscopic Survey.

November 2013

05.11.13 (Tuesday)
12:00
"Mapping progenitor characteristics to supernova classes and transient features"
Joe ANDERSON (ESO, Chile)
Abstract
12.11.13 (Tuesday)
12:00
"A search for faint companions of the nearest stars with CanariCam and VHS"
Bartek GAUZA (Instituto de Astrofisica de Canarias, IAC)
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"A search for faint companions of the nearest stars with CanariCam and VHS"

Bartek GAUZA (Instituto de Astrofisica de Canarias, IAC)

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.
27.11.13 (Wednesday)
15:30
"Spatially resolving the gas dynamics over the surface of red supergiants with the Very Large Telescope Interferometer"
Keiichi OHNAKA (MPIfR, MPG, Bonn)
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"Spatially resolving the gas dynamics over the surface of red supergiants with the Very Large Telescope Interferometer"

Keiichi OHNAKA (MPIfR, MPG, Bonn)

Abstract

The mass-loss mechanism in red supergiants is one of the long-standing problems in stellar astrophysics. For solving this problem, it is crucial to probe the dynamics of the outer atmosphere. The milliarcsecond angular resolution achieved by infrared long-baseline interferometry provides us with the only way to spatially resolve this key region. We present high spatial and high spectral resolution observations of the 2.3 micron CO lines in the red supergiants Betelgeuse and Antares using the Very Large Telescope Interferometer (VLTI). We have succeeded in "velocity-resolved" aperture-synthesis imaging of stars for the first time, which allows us to probe not only inhomogeneous structures over the surface of stars but also their kinematics, as routinely done in solar physics. We have detected vigorous upwelling and downdrafting motions of large CO gas clumps (as large as the radius of the stars) at up to 20-30 km/s within 1.5 stellar radii. Our VLTI observations suggest the following new picture: the material within 1.5 stellar radii is strongly stirred possibly by magnetohydrodynamical processes and/or pulsation and may be violently flung out.
29.11.13 (Friday)
12:00
"Terzan 5: the remnant of a pristine fragment of the Galactic Bulge?"
Alessio MUCCIARELLI (Univ. Bologna)
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"Terzan 5: the remnant of a pristine fragment of the Galactic Bulge?"

Alessio MUCCIARELLI (Univ. 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.

October 2013

03.10.13 (Thursday)
12:00
"The VVV-SkZ Pipeline: How to get Automatic PSF-fitting photometry from VISTA surveys. Present status and future implementations"
Francesco MAURO (Universidad de Concepcion, Chile)
Abstract
07.10.13 (Monday)
12:00
"Kinematics and chemical elements of the very metal poor Globular Cluster NGC 4372"
Nikolay KACHAROV (University of Heidelberg)
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"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.
08.10.13 (Tuesday)
12:00
"GRBs in 2013: Progress and recent results"
Thomas KRUEHLER (ESO, Chile)
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"GRBs in 2013: Progress and recent results"

Thomas KRUEHLER (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.
16.10.13 (Wednesday)
15:30
"A unifying view of AGN sub-pc scale structure : pushing the limit of infrared interferometry"
Makoto KISHIMOTO (MPIFR, Bonn)
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"A unifying view of AGN sub-pc scale structure : pushing the limit of infrared interferometry"

Makoto KISHIMOTO (MPIFR, Bonn)

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.

September 2013

9.09.13 (Monday)
12:00
"Capabilities and scientific prospects of the VLTI-GRAVITY instrument"
Pierre KERVELLA (Observatoire de Paris-Meudon)
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"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.
10.09.13 (Tuesday)
12:00
"Integral field spectroscopy of nearby supernova hosts galaxies"
Ana MOURAO (CENTRA, U. Lisboa)
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"Integral field spectroscopy of nearby supernova hosts galaxies"

Ana MOURAO (CENTRA, U. Lisboa)

Abstract

We present a study of 44 nearby supernova host galaxies observed with IFS by the CALIFA-Calar Alto Legacy. We complement our analysis with data from previous observations of 23 galaxies that hosted supernovae. We show that the 2D maps of the galaxy properties, obtained from the analysis of the ionized gas and the stellar population, allow us to compare the global properties of the galaxies with the properties at the projected position of the supernova (SN). According to our results SNe Ib/c are more associated with HII regions than SNe II. SNe Ia are associated with regions with lower current star formation and older stellar populations. SNe Ia are also associated with higher metallicity regions, comparing to SN Ib/c and SN II.
11.09.13 (Wednesday)
15:30
"Molecular hydrogen in the halo of a galaxy at z~0.56"
Neil CRIGHTON (MPIA)
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"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.
12.09.13 (Thursday)
12:00
"Studies on galaxy formation using high resolution deep imaging of high-z QSO fields"
Yiping WANG (National Astronomical Observatories, Beijing, China)
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"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.
23.09.13 (Monday)
12:00
"Multiple stellar systems"
Petr ZASCHE (Charles University, Prague)
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"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?

August 2013

12.08.13 (Monday)
12:00
"A deeper look on thick discs using data from the Spitzer Survey of Stellar Structure in Galaxies (S4G)"
Sebastian COMERON (U. Oulu)
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"A deeper look on thick discs using data from the Spitzer Survey of Stellar Structure in Galaxies (S4G)"

Sebastian COMERON (U. 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.
14.08.13 (Wednesday)
12:00
"The starburst clusters in Galactic center"
Adriane LIERMANN (AIP)
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"The starburst clusters in Galactic center"

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.
20.08.13 (Tuesday)
12:00
"The mid-infrared properties of local active galactic nuclei at high-angular resolution"
Daniel ASMUS (MPIfR, Bonn)
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"The mid-infrared properties of local active galactic nuclei at high-angular resolution"

Daniel ASMUS (MPIfR, Bonn)

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.
21.08.13 (Wednesday)
15:30
"Rapid-response mode VLT/UVES spectroscopy of gamma-ray burst afterglows "
Paul VREESWIJK (Weizmann Institute of Science)
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"Rapid-response mode VLT/UVES spectroscopy of gamma-ray burst afterglows "

Paul VREESWIJK (Weizmann Institute of Science)

Abstract

Gamma-ray bursts are brief but very powerful flashes of gamma rays, discovered in the 1960s. Until the 1990s it was unclear whether they had a Galactic or cosmological origin. The discovery of their X-ray, optical and radio afterglows in 1997 settled the debate in favour of the cosmological camp. One of the first afterglows discovered was shown to be connected to a core-collapse supernova explosion, which suggested, along with the LGRB host galaxies being actively star-forming, that the progenitor of a GRB is a very massive star. Because of their incredible luminosity, GRBs and their afterglows can be detected from any redshift; the current redshift record is z=8.2. The combination of redshift range and origin in massive-star forming regions, makes GRBs excellent probes of the chemical evolution and star-formation history of the universe. Since 2005 the Swift satellite is providing rapid and accurate locations of about 90 GRBs per year. Combined with the rapid response mode available at the Very Large Telescope, this has allowed us to perform time-resolved high-resolution spectroscopy of GRB afterglows with the Ultra-violet and Visual Echelle Spectrograph (UVES). In this talk we present results from our on-going survey of GRB afterglows with UVES, with a strong focus on the detection of absorption-line variability and what we can infer from that.
27.08.13 (Tuesday)
12:00
"Metallicities and alpha-enhancement of red giant stars in 51 Milky Way globular clusters: homogeneous scale and multiple populations"
Bruno DIAS (ESO, Chile)
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"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])

July 2013

9.07.13 (Tuesday)
12:00
"The cosmic origin of Sulphur"
Nils RYDE (Lund Observatory)
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"The cosmic origin of Sulphur"

Nils RYDE (Lund Observatory)

Abstract

Sulphur is one of the elements that could be used to infer the star-formation rate of a stellar population. It is a good choose since sulphur is not depleted onto dust, and can therefore also be used out to cosmological distances. However, the Galactic Chemical Evolution of sulphur, i.e. its cosmic origin, is strangely enough still under debate. Only recently, there were three different observational trends of its evolution published. One reason for this might be the different difficulties with the available spectral diagnostics used when determining the sulphur abundances in stars. Here, I will present a recent study where we use a new diagnostic in the near-IR. From a physical point of view, we argue that this should be the preferred one to be use.
22.07.13 (Monday)
12:00
"A New Population of Luminous Heavily Dust Reddened Quasars at Redshift ~2 from Current Wide-Field Infrared Surveys"
Manda BANERJI (U. College London)
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"A New Population of Luminous Heavily Dust Reddened Quasars at Redshift ~2 from Current Wide-Field Infrared Surveys"

Manda BANERJI (U. College London)

Abstract

I will discuss a new population of heavily dust-reddened intrinsically luminous Type 1 quasars at redshifts of ~2 discovered using new sensitive wide-field infrared surveys (e.g. UKIDSS, VISTA, WISE). These broad-line quasars are some of the most bolometrically luminous quasars known with extremely large black-hole masses and evidence for strong outflows affecting the broad-line profiles. Despite their extreme properties, they have been previously unstudied. The typical dust extinctions are Av ~2.5 mags comparable to SMGs at similar redshifts and this makes these quasars invisible in optical surveys like SDSS. I will discuss the implications of these new quasars for galaxy formation and coeval galaxy and black-hole growth, present our ongoing spectroscopic follow-up program to find larger numbers of them and discuss some follow-up observations at far infra-red to submillimeter wavelengths that confirm that these quasars reside in massive starburst hosts. Based on the following papers + some new results: Banerji et al. (2012), MNRAS, 427, 2275
http://adsabs.harvard.edu/abs/2012MNRAS.427.2275B
Banerji et al. (2013), MNRAS, 429L, 55
http://adsabs.harvard.edu/abs/2013MNRAS.429L..55B
26.07.13 (Friday)
12:00
"Discretized Aperture Mapping for high contrast imaging?"
Fabien PATRU (ESO, Chile)
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"Discretized Aperture Mapping for high contrast imaging?"

Fabien PATRU (ESO, Chile)

Abstract

Three main approaches are used in high-contrast imaging to recover the phase of a pupil of a telescope in the presence of turbulence: post-treatment (e.g. speckle imaging or differential imaging), correction in real-time (e.g. active or adaptive optic) and spatial filtering of the phase residuals (e.g. pin-hole or single-mode fiber). In that context, DAM (Discretized Aperture Mapping) appears as an original filtering device able to improve existing optical systems. DAM is a low-pass optical filter able to remove part of the phase residuals in a wave-front, allowing high contrast imaging over a finite field of view imaged by the present class of telescopes equipped with adaptive optics. We will show here the first theoretical and laboratory results in this new promising area. We will discuss how DAM can be coupled with complementary techniques (e.g. coronography or angular differential imaging) to improve both the contrast ratio and the tiny separation between an exoplanet and its hosting star.

June 2013

03.06.13 (Monday)
12:00
"Supernova spectra below strong circum-stellar interaction"
Giorgos LELOUDAS (Dark Cosmology Centre)
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"Supernova spectra below strong circum-stellar interaction"

Giorgos LELOUDAS (Dark Cosmology Centre)

Abstract

We construct spectra of supernovae interacting strongly with a circum-stellar medium (CSM) by adding SN templates, a black-body continuum and an emission-line spectrum. In a Monte Carlo simulation we vary a large number of parameters such as the SN type, brightness and phase, the strength of the CSM interaction, the extinction and the S/N of the observed spectrum. We generate 500 spectra and distribute them to 10 different human classifiers. Our purpose is to understand and quantify how the classification of the spectra depends on the different simulation parameters. When studying thermonuclear SNe interacting strongly with a CSM (SNe Ia-CSM) we discover that there is no luminosity bias explaining the observed association of SNe Ia-CSM to 91T-like objects. We therefore suggest that the luminous 91T-like subclass of SNe Ia originates from single degenerate progenitors. We show that the flux ratio of the underlying SN to the black-body continuum (hereafter f_V) is the single important parameter affecting the composite spectrum's appearance and classification. Other parameters, such as extinction, S/N, width and strength of the emission lines, do not play a significant role. Thermonuclear SNe get progressively classified as Ia-CSM, IInS (a class that we introduced for the needs of this project) and IIn as f_V decreases. We are able to quantify this effect and we determine that SNe Ia-CSM are found at the (un-extincted) magnitude range -19.5 > M > -21.6, in very good agreement with observations, and that the faintest SN IIn that can hide a SN Ia has M = -20.1. Despite the spectroscopic similarities between SNe Ibc and SNe Ia, the number of misclassifications between these types was very small in our experiment. Combined with the SN luminosity function needed to reproduce the observed SN Ia-CSM luminosities, we suggest that SN Ibc contamination within this sample is, at most, minimal. The fictitious broad-lined SNe Ic interacting with a CSM are easy to recognize but none has been found in nature. Therefore, these events are intrinsically rare, if they exist at all. We show how Type II spectra transition to IIn and how the Ha profiles vary with f_V. Since SN are confidently identified as IIP for f_V > 0.15, we are able to place constraints on the nature of the faintest SNe IIn. We argue that our simplified model is a good first order approximation for a variety of conditions and demonstrate that it is in good agreement with real data.
05.06.13 (Wednesday)
12:00
"Eyes for the extreme universe, very high energy gamma ray astronomy"
Julian KRAUSE (Max-Planck Institute for Physics, Munich)
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"Eyes for the extreme universe, very high energy gamma ray astronomy"

Julian KRAUSE (Max-Planck Institute for Physics, Munich)

Abstract

Very high energy (VHE) gamma ray astronomy uses ground based facilities to open a window to the universe at photon energies above ~50 GeV. After the discovery of the first source (the Crab Nebula) in 1989 by the Whipple Observatory the field has undergone a major development during the last decades which lead to the discovery of more than 140 sources and many unexpected results. First an introduction to the so called imaging air Cherenkov technique will be given, being currently the most successful technique in the energy range of ~50 GeV up to several tenths of TeV. Then I will give a short overview of the currently operating experiments (MAGIC, H.E.S.S., and VERITAS) and of their capabilities in the sense of sensitivity, angular resolution, and energy resolution. Before I will discuss which kind of objects are known to emit VHE-gamma rays, I will summarize the main physical processes which lead to the production of gamma rays. As of today, gamma-ray observations are the only successful way to trace highly relativistic protons, the main component of cosmic rays. In the last part of the talk I will present recent result obtained by MAGIC of the supernova remnant W51C as an example of the role of the field towards answering the question for the origin of galactic cosmic rays.
07.06.13 (Friday)
12:00
"Searching the WISE sky"
Andrew BLAIN (University of Leicester)
Abstract
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"Searching the WISE sky"

Andrew BLAIN (University of Leicester)

Abstract

I will describe the WISE all-sky infrared survey, and some of the extragalactic follow-up work done on ultraluminous galaxies, especially in comparison with existing samples of high-redshift luminous objects.
11.06.13 (Tuesday)
12:00
"Status of the Stratospheric Observatory for Infrared Astronomy (SOFIA)"
B-G ANDERSSON (SOFIA Science Center)
Abstract
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"Status of the Stratospheric Observatory for Infrared Astronomy (SOFIA)"

B-G ANDERSSON (SOFIA Science Center)

Abstract

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is now performing scientific observations. With an available wavelength coverage from the visual to sub-mm wavelengths and a long life time - including planned instrument upgrades, SOFIA will provide critical resource for the astronomical community for the next decade and beyond. Current and expected SOFIA instruments provide heterodyne spectroscopy in the THz band, including the line of [O I], [C II] and [N II] as well as OH, HD and many other hydrides, at high spectral resolution. Echelle spectroscopy in the Mid-infrared (MIR) which will allow observations of e.g. fine-structure lines of and H2 pure rotational lines. These will help address questions of interstellar chemistry and physics in star forming regions, PDRs and galaxies. Mid-infrared (MIR) grism spectroscopy, of e.g. dust and ices, can be used to address questions of the freeze-out of molecules from the gas phase to better understand the formation, destruction and characteristics of interstellar ices. Imaging in the MIR and FIR and FIR polarimetry can provide a more complete picture of the temperature, density and magnetic field structure of e.g. star forming cores. I will highlight the current and expected capabilities of SOFIA and some of the early science results achieved.
12.06.13 (Wednesday)
16:00
"The asteroids and the early Solar System: from 3-D shape modeling to planetary migration"
Benoit CARRY (ESA)
Abstract
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"The asteroids and the early Solar System: from 3-D shape modeling to planetary migration"

Benoit CARRY (ESA)

Abstract

The small bodies of our Solar System are the left-over of the bricks that accreted to form the planets some 4.6 Gyrs ago. Owing to their small sizes, their original composition and mineralogy, trackers for the conditions in which they were formed, has been preserved intact in their interiors. Over the last decade, the always increasing number of discovery together with photometric measurements from all-sky surveys has allowed us to tap into the compositional detail of tens of thousands of asteroids, unveiling the complex dynamical history of our Solar System. Nevertheless, study of asteroids still present challenges. Only half of the compositional classes have a mineralogical interpretation or are linked with known meteorites. Our knowledge of their physical properties, including their density, perhaps the most fundamental property to understand their composition and internal structure, is limited to a couple of hundred objects only. After an introductory overview of our current understanding of the early Solar System as inferred from asteroid observations, I will present recent advances in 3-D shape modeling that allow to derive critical quantities, such as the density, to determine the asteroid-meteorite links that are still to be found. Finally, I will discuss how upcoming facilities such as ALMA or Gaia, are expected to revolutionize the field.
13.06.13 (Thursday)
12:00
"Kinematics of NGC 6388 and new constraints on the IMBH mass from the radial velocity of individual stars"
Barbara LANZONI (U Bologna)
Abstract
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"Kinematics of NGC 6388 and new constraints on the IMBH mass from the radial velocity of individual stars"

Barbara LANZONI (U Bologna)

Abstract

By using SINFONI@VLT, we measured the radial velocity of 52 individual stars in the very central region (r<2”) of the Galactic globular cluster NGC6388, which is suspected to host an intermediate-mass black hole (IMBH). Together with the radial velocities obtained with FLAMES@VLT for almost 300 stars out to ~600" from the centre, this unique dataset allowed us to derive, for the very first time, the entire cluster velocity dispersion profile from individual radial velocity measurements. We find no evidence of a central cusp in the velocity dispersion profile and we measure a central value well below the one derived by Lutzgendorf et al. (2011) from integrated light spectroscopy. Hence, we do not confirm the existence of an IMBH in the core of this cluster. This study also highlights the urgence of underastanding in which cases (if any) the velocity dispersion of Galactic globular clusters can be derived from integrated light spectroscopy.
17.06.13 (Monday)
16:00
"Dwarf galaxies and star clusters old and not so old: exploring the links"
Gary DA COSTA (ANU)
Abstract
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"Dwarf galaxies and star clusters old and not so old: exploring the links"

Gary DA COSTA (ANU)

Abstract

In the first part of the colloquium I will use new results for the little-studied distant halo globular cluster NGC 5824 to explore the possiblity that globular clusters with internal heavy element abundance spreads represent the former nuclei of now disrupted dwarf galaxies. Then in the second part of the presentation I will discuss what recent results for ~1 Gyr old clusters in the Large Magellanic Cloud may be telling us about the origin of the ubiquitous sodium-oxygen abundance anti-correlation seen in most, if not all, Galactic globular clusters.
19.06.13 (Wednesday)
16:00
"Signatures of rocky and giant planets in the chemical composition of solar-type stars"
Jorge MELENDEZ (U Sao Paulo)
Abstract
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"Signatures of rocky and giant planets in the chemical composition of solar-type stars"

Jorge MELENDEZ (U Sao Paulo)

Abstract

Recent ultra high precision studies (Melendez et al. 2009, 2012; Ramirez et al. 2009, 2010) have shown that the chemical composition of the Sun is abnormal when compared to solar twins (stars essentially identical to our Sun). The Sun is deficient in refractory elements, in an amount consistent with the combined mass of terrestrial planets and asteroids. The chemical anomalies in the Sun are very well explained by a mixture of Earth-like and carbonaceous-chondrite-like material (Chambers, 2010). Thus, the processes that lead to terrestrial planet formation seem to have locked in the rocky planets the refractory material that is missing in the Sun. We have also studied the signature of giant planets using the binary pair 16 Cyg (Ramirez, Melendez, Cornejo et al. 2011), which is composed of two solar analogs, one of them hosting a giant planet. I will review the signatures of planet formation and our efforts on both high precision chemical abundances (0.01 dex) and planet detection around solar twins with our ongoing Large Programme with HARPS, in order to study the planet-star connection with unprecedented detail.
28.06.13 (Friday)
16:00
"Near IR imaging and spectroscopy with the MMT and Magellan Infrared Spectrograph"
Igor CHILINGARIAN (Smithsonian Astrophysical Observatory)
Abstract
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"Near IR imaging and spectroscopy with the MMT and Magellan Infrared Spectrograph"

Igor CHILINGARIAN (Smithsonian Astrophysical Observatory)

Abstract

I will review the current capabilities and performance of the MMT and Magellan Infrared Spectrograph (MMIRS) working in imaging, longslit and multiobject spectroscopic modes. I will present the data reduction pipeline providing Poisson limited sky subtraction quality for low- and intermediate-resolution spectroscopic observations (R=1200..2500). Even in the low-resolution setup this enables instrument users to observe very faint targets such as high-redshift emission line galaxies. The sky subtraction is performed using the modified Kelson (2003) algorithm on dithered pairs allowing us to handle short slitlets in the MOS regime. A similar approach with minor modifications can be applied to NIR IFU data with both, on-target and off-target sky observation modes. I will conclude with several scientific highlights based on MMIRS data including the studies of atmospheres of exoplanets and intermediate to hight-redshift extragalactic research.

May 2013

02.05.13 (Thursday)
12:00
"Resolving the BLR of the Quasar 3C273 with differential interferometry on AMBER"
Romain PETROV (Laboratoire LAGRANGE, OCA-UNS-CNRS)
Abstract
03.05.13 (Friday)
12:00
"Stellar Variability: Impact on the detection and characterization of exoplanets"
Isabelle BOISSE (U. Porto)
Abstract
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"Stellar Variability: Impact on the detection and characterization of exoplanets"

Isabelle BOISSE (U. Porto)

Abstract

Although extremely efficient, the radial-velocity (RV) technique to search and characterize planets is, however, an indirect method (as well as photometric transit detection or astrometry). One of the problems with this is the fact that periodic RV variations can in some cases be caused by some other mechanisms, not related to the presence of low-mass companions. Phenomena such as stellar pulsation, inhomogeneous convection, spots or magnetic cycles can prevent us from finding planets, they might degrade the parameters estimation, or give us false candidates, if they produce a stable periodic signal. We will consider the different kind of «noise »
that are generated by stars, as well as the methods proposed and used to overcome this issue.
03.05.13 (Friday)
14:30
"Towards a more comprehensive understanding of exo-planetary worlds with direct imaging"
Laurent PUEYO (STScI)
Abstract
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"Towards a more comprehensive understanding of exo-planetary worlds with direct imaging"

Laurent PUEYO (STScI)

Abstract

Direct imaging mitigates selection effects inherent to the currently known exo-planetary population since it is sensitive to objects in an orbital space orthogonal to the one available with indirect methods. Upcoming campaigns will survey young and adolescent stars and probe for signatures of their formation history using instruments designed for high-contrast imaging. In this presentation I will discuss the wealth of information accessible using such surveys and illustrate preliminary results from such campaigns. I will describe current methods and detail algorithmic progress pioneered by our team in order to identify and characterize with direct imaging the infrared radiation of young exo-planets orbiting nearby stars. I will illustrate how to take advantage of these techniques to analyze data from one of the largest homogenous direct imaging surveys to date: the aggregate of all HST-NICMOS coronagraphic observations carried out between 1998 and 2006. I will then present recent results obtained with the Project P1640 Integral Field Spectrograph, installed at the Palomar Hale Telescope, with a particular emphasis on the techniques we have developed for this class simultaneous multi-wavelengths observations and their impact on the characterization of the planetary systems already observed during the earlier stages of our 100 night survey.
06.05.13 (Monday)
12:00
"Measuring brightness asymmetries of red giants and supergiants with the VLTI/AMBER"
Pierre CRUZALEBES (Observatoire Cote d'Azur)
Abstract
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"Measuring brightness asymmetries of red giants and supergiants with the VLTI/AMBER"

Pierre CRUZALEBES (Observatoire Cote d'Azur)

Abstract

High-angular-resolution observations of evolved stars reveal time-varying and large-scale deviations with respect to homogeneous photospheres. I will present the results of multiple observations, distributed over a two years period (2009-2011), made with VLTI/AMBER in the aim to reveal surface brightness asymmetries for 16 red giants and supergiants. Fine absolute calibration of raw instantaneous spectro-interferograms at the spectral channel level and fitting with chromatic atmospheric models allow to give reliable estimates of limb-darkened angular diameters. Fundamental stellar parameters are derived, linked to the departure from centro-symmetry. Correlations with Tc abundance and accuracy of astrometric parallax are searched.
07.05.13 (Tuesday)
12:00
"Preliminary results from bulge globular clusters proper motions"
Sergio ORTOLANI (U. Padova)
Abstract
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"Preliminary results from bulge globular clusters proper motions"

Sergio ORTOLANI (U. Padova)

Abstract

Preliminary results of new, ground based CCD, proper motion measurements of galactic globular clusters projected in the direction of the bulge are presented. Most of them have more than 10 years of time base, and give reliable transverse motions in spite of their surprisingly small values. Combining the proper motions with the radial velocities and their positions (obtained from new distance measurements) we obtained the orbits using a model of gravitational potential optimized in the inner regions of the Galaxy. A new scenario of the properties of these clusters is derived, with at least two different families characterized by different kinematics. Implications on the size of the galaxy, the total number of inner bulge clusters and their formation are discussed.
14.05.13 (Tuesday)
12:00
"The Planet next door: An Earth-mass world orbiting Alpha Centauri B "
Xavier DUMUSQUE (U. Geneve)
Abstract
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"The Planet next door: An Earth-mass world orbiting Alpha Centauri B"

Xavier DUMUSQUE (U. Geneve)

Abstract

Nowadays, after having found hundreds of exoplanets, the radial-velocity (RV) technique starts to be limited by intrinsic stellar signals. Indeed, at the level of the best spectrographs, one starts to see the effects induced by stellar pressure waves, convection, surface activity coupled with stellar rotation, and magnetic cycles. The questions of how to extract and analyse the different types of stellar signals from RV data, and how to mitigate their contribution will be presented in detail. As result of this work, the smallest exoplanet detected with the RV technique have been announced. This planet, having a similar mass to Earth is also the closest one to the Solar System.
15.05.13 (Wednesday)
16:00
"A new spin on the Carina dwarf spheroidal galaxy"
Giuseppe BONO (Univ. of Rome Tor Vergata)
Abstract
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"A new spin on the Carina dwarf spheroidal galaxy"

Giuseppe BONO (Univ. of Rome Tor Vergata)

Abstract

Dwarf spheroidal (dSph) galaxies play a crucial role in many open astrophysical problems. We will outline some of them and we will focus our attention on stellar populations in the Carina dSph. In particular, we will discuss recent photometric and spectroscopic findings concerning the metallicity distribution and the identification of kinematic substructures. Finally, we will also discuss the pulsation properties of variable stars in nearby dwarf spheroidals and the role that they can play as stellar tracers.
16.05.13 (Thursday)
12:00
"Science with the Virtual Observatory"
Amelia BAYO (ESO / MPIA, Heidelberg)
Abstract
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"Science with the Virtual Observatory"

Amelia BAYO (ESO / MPIA, Heidelberg)

Abstract

The amount of public archival data available and multi-wavelength all sky survey missions are changing the way astronomical research is done. Although detailed studies on individual objects are of course necessary, the development of new tools and methodologies that ease the analysis of large amounts of multi-wavelength data in homogeneous and efficient ways is becoming mandatory. In this context, already in the early 2000 a world-wide philosophy was born: the "Virtual Observatory" that on the base of standardization of the data formats and data transfer protocols seeks to maximize the time for "real" science. In this talk I will give a brief introduction on how the Virtual Observatory was born and I will illustrate how useful it is with a number of published science papers based on this philosophy.
20.05.13 (Monday)
12:00
"Proto-groups at z∼2 in zCOSMOS-deep"
Catrina DIENER (ETH Zurich)
Abstract
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"Proto-groups at z∼2 in zCOSMOS-deep"

Catrina DIENER (ETH Zurich)

Abstract

The zCOSMOS-deep sample contains 3500 galaxies with spectroscopic redshifts between 1.8 < z < 3 in the COSMOS field. We devise a group finder that takes into account the large measurement uncertainties at this redshift and identified 42 associations in this redshift range. They each contain three to five galaxies that lie within 500 kpc in projected distance and within 700 km/s in velocity. Based on the extensive analysis of mock catalogues generated from the Millennium simulation, I will discuss the properties of the observed structures as well as their evolution until redshift zero. Furthermore I will present a proto-cluster at redshift z = 2.45, that was dis- covered recently in follow-up observations of 7 of the proto-groups in zCOSMOS- deep. This interesting structure has so far 11 spectroscopically confirmed mem- bers.
22.05.13 (Wednesday)
16:00
"Magnetic star-disk interaction and the angular momentum evolution of young stars"
Jerome BOUVIER (Institut de Planetologie et d'Astrophysique de Grenoble, IPAG)
Abstract
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"Magnetic star-disk interaction and the angular momentum evolution of young stars"

Jerome BOUVIER (Institut de Planetologie et d'Astrophysique de Grenoble, IPAG)

Abstract

Young solar-type stars, the so-called T Tauri stars, possess strong and complex magnetic fields, whose strength and topology are now directly measured through spectropolarimetric techniques. These strong fields disrupt the inner accretion disk over a distance of a few stellar radii, thus leading to magnetic funnel flows connecting the disk inner edge to the central star. Accretion shocks are expected to develop at the stellar surface near the magnetic poles, as the magnetically-channeled free-falling material hits the photosphere. Also, a non axisymmetric inner disk warp is expected to result from the interaction with an inclined stellar magnetosphere, which lifts up the disk material away from the central plane. In this talk, I will provide a summary of the observational evidence we have for magnetospheric accretion in young stars (magnetic fields, funnel flows, hot spots, disk warps) and will show how new COROT+Spitzer simultaneous observations nicely support and generalize this view. I will briefly mention how planetary migration may be affected by this process and will insist on the central role magnetospheric accretion plays in our current understanding of the angular momentum evolution of young stars. Finally, I will highlight the tentative causal links that appear to emerge between protoplanetary disk lifetimes, massive planet formation, rotational evolution, and lithium depletion in solar-type stars.
23.05.13 (Thursday)
12:00
"Exploring giant planet aurorae with emissions from H3+"
Henrik MALIN (U. Leicester)
Abstract
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"Exploring giant planet aurorae with emissions from H3+"

Henrik MALIN (U. Leicester)

Abstract

The auroral process is when energetic particles impact upon the atmosphere, producing emissions. By observing these emissions we can not only glean the physical properties of the medium from which they were emitted, we can also address of the particle precipitation and physical process that delivered the particles upon the atmosphere. In the infrared, emission produced by this phenomenon can be observed from the molecular ion H3+. In this seminar, we explore what we can learn about the auroral process at Jupiter, Saturn, Uranus, and Neptune by observing emissions from H3+.
28.05.13 (Tuesday)
12:00
"Cepheids in Galactic Open Clusters: An All-sky Census in 8D "
Richard ANDERSON (Obs. de Geneve)
Abstract
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"Cepheids in Galactic Open Clusters: An All-sky Census in 8D"

Richard ANDERSON (Obs. de Geneve)

Abstract

We report on our recent eight-dimensional all-sky census of Cepheids belonging to Galactic open clusters that employs spatial, kinematic, and population-specific data. Our analysis has allowed us to confirm 15 cluster Cepheids (CCs) known in the literature and to identify 5 very good candidate CCs. Details on the analysis, including data selection and homogenization are provided. In addition to the literature data employed, we conducted observational radial velocity campaigns on both hemispheres. This program led to the discovery of the spectroscopic binary nature of at least 8 Cepheids. Some of these cases are highlighted here, including one for which a precise orbital solution was obtained. Our data mining approach to membership has the benefit of being transparent and self-consistent, and enables ranking of membership confidence according to the probabilities computed. However, some limitations of the literature data, especially for open clusters, are apparent. These limitations are discussed in the context of a calibration of the Galactic period-luminosity relationship using our bona-fide CC sample. Our method will find application in upcoming large surveys such as LSST and Gaia.
29.05.13 (Wednesday)
16:00
"In and around Cygnus OB2"
Fernando COMERON (ESO, Chile)
Abstract
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"In and around Cygnus OB2"

Fernando COMERON (ESO, Chile)

Abstract

TBA
31.05.13 (Friday)
12:00
"Life in the Universe"
Jorge MELNICK (ESO, Chile)
Abstract
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"Life in the Universe"

Jorge MELNICK (ESO, Chile)

Abstract In 1960 the US radio astronomer Frank Drake started a search of radio signals from extraterrestrial technologically advanced civilizations using the Green Bank radio telescope. In 1961 the US National Science Foundation asked Drake to organize a meeting to discuss the possibility of finding other civilizations in our Galaxy. In preparation for that meeting, Drake wrote down the main factors that would need to be addressed to understand the odds of finding radio signals from extraterrestrial intelligent beings. The product of these factors is what is now known as the Drake Equation. Advances in many fields of science since 1960 enable us today to use Drake's equation to make scientifically sound estimates of the number of intelligent civilizations expected to exist in our Galaxy. In this presentation I will show that using the best available data, the probability of finding intelligent life in other planets is still critically dependent of Drake's longevity parameter: how long does a technological civilization survives to natural and people induced threats?

April 2013

1.04.13 (Monday)
12:00
"The Herschel Planetary Survey: HerPlaNS"
Djazia LADJAL (University of Denver, USA)
Abstract
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"The Herschel Planetary Survey: HerPlaNS"

Djazia LADJAL (University of Denver, USA)

Abstract

HerPlaNS is a Herschel Open Time program that exploits the unprecedented spatial resolving power in the far infrared (from 50um to 670um) of the Herschel Space Observatory to investigate a sample of 11 planetary nebulae (PNe). The aim of the program is to study the distribution of cold dust in the nebulae, using the PACS and SPIRE imaging modes, and to diagnose the physical conditions of the gas component using the PACS and SPIRE spectroscopy modes. The novelty of the study (apart from exploring a new wavelength range) is that our spectroscopy observations are spatially resolved which then allows us to compare the data to narrow band observations from Hubble and link the low energy regime of the PN to the high energy regime. PNe are unique objects that can be observed from the X-ray to the radio regime and the HerPlaNS data are essential in that they compliment the wealth of literature data we have at other wavelengths. This allows us to build a more complete picture of the PNe system in terms of evolution and energetics. In this presentation, I would like to introduce the HerPlaNS program, show its scientific potential and present some of our first results.
2.04.13 (Tuesday)
12:00
"Testing the Unification Model for AGN in the Infrared"
Cristina RAMOS ALMEIDA (IAC, Spain)
Abstract
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"Testing the Unification Model for AGN in the Infrared"

Cristina RAMOS ALMEIDA (IAC, Spain)

Abstract

I will present recent results on SED+spectroscopy fitting with CLUMPY torus models using subarcsecond resolution infrared data and a Bayesian approach. Our aim is to constrain and compare the properties of Type-1 and Type-2 Seyfert tori. We find that these dusty tori have physical sizes smaller than 10 pc radius, as derived from our fits. Unification schemes of AGN account for a variety of observational differences in terms of viewing geometry. However, we find evidence that strong unification may not hold, and that the immediate dusty surroundings of Type-1 and 2 Seyfert nuclei are intrinsically different in terms of covering factor. Finally, I will discuss the role of host galaxy obscuration in the fits.
3.04.13 (Wednesday)
16:00
"A precision distance to the Large Magellanic Cloud from eclipsing binaries and Cepheid variables"
Wolfgang GIEREN (Universidad de Concepción, Chile)
Abstract
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"A precision distance to the Large Magellanic Cloud from eclipsing binaries and Cepheid variables"

Wolfgang GIEREN (Universidad de Concepción, Chile)

Abstract

I will report on the work of our group to improve the distance determination to the Large Magellanic Cloud to two percent, using eight unique eclipsing binary systems in the LMC. This new measurement represents a milestone for the calibration of the cosmic distance scale and improves the accuracy of the value of the Hubble constant. I will also report on the work of our group on Milky Way and LMC Cepheids which have yielded an independent precise distance to the LMC from the Infrared Surface Brightness Method, which serves as a check on the result from the eclipsing binaries
15.04.13 (Monday)
12:00
"Pushing AMBER to the limits"
Florentin MILLOUR (Observatoire de la Côte d'Azur)
Abstract
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"Pushing AMBER to the limits"

Florentin MILLOUR (Observatoire de la Côte d'Azur)

Abstract

We have been conducting since 2011 a series of test campaigns to improve the AMBER observing strategy. The result is a jump of 2 magnitudes on the AMBER limiting magnitude. This improvement opens a wealth of new possibilities for AMBER, like increasing significantly the number of observable AGNs, accessing the AGNs Broad Line Region geometry, catching stellar types which were unreachable before, among other. I will briefly describe that observing strategy and show a few new results obtained with it.
16.04.13 (Tuesday)
12:00
"Eclipsing white dwarf binaries"
Steven PARSONS (Universidad de Valparaiso)
Abstract
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"Eclipsing white dwarf binaries"

Steven PARSONS (Universidad de Valparaiso)

Abstract

In recent years multi-colour and transient surveys have lead to a large increase in the number of eclipsing white dwarf plus main-sequence star binaries. These binaries offer us a chance to test some of the fundamental concepts underpinning a wide range of astrophysical problems, ranging from exoplanet studies and supernova Ia, to compact binary evolution and the age of the Galaxy. I will present the results of our high-precision studies of these systems and show that they are ideal for testing both the white dwarf and low-mass star mass-radius relationships as well as models of binary evolution.
17.04.13 (Wednesday)
16:00
"The SINFONI view of the structure and internal workings of redshift 2 star-forming galaxies"
Alvio RENZINI (INAF, Padova Observatory)
Abstract
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"The SINFONI view of the structure and internal workings of redshift 2 star-forming galaxies"

Alvio RENZINI (INAF, Padova Observatory)

Abstract

Major imaging and spectroscopic surveys of high redshift galaxies have delivered large samples of these objects that have allowed us to measure global quantities such as sizes, star formation rates and stellar masses, thus revealing some fundamental trends followed by galaxy populations. For a small, but representative number of them, it became possible to go further and study their internal structure and kinematics in greater detail. This has been accomplished with the Adaptive-Optics-fed SINFONI 3D spectrograph at the ESO VLT, that has delivered Halpha imaging and kinematics with ~1 kpc resolution for a few dozen galaxies at redshift ~2. These observations have revealed large rotating disk galaxies, along with other more compact and velocity dispersion dominated, whereas others appear to be mergers. Such large disks appear to host several actively star-forming clumps and are characterized by a much higher velocity dispersion compared to local galaxies. The presence of strong galactic winds, inferred from the profile of emission lines, adds further diversity of these galaxies compared to local spirals of similar stellar mass. Together with pioneering sub-mm observations, a detailed characterization of these galaxies is rapidly emerging which is providing us with fresh clues on galaxy formation and evolution.
22.04.13 (Monday)
12:00
"Multiplicity and fast accretion of ordinary chondrite parent bodies"
Pierre VERNAZZA (ESO, Garching)
Abstract
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"Multiplicity and fast accretion of ordinary chondrite parent bodies"

Pierre VERNAZZA (ESO, Garching)

Abstract

Planetesimal formation in the early Solar System is a very complex process through which initially submicron-sized dust grains evolve into rocky and/or icy planetesimals. The physical growth is accompanied by chemical, isotopic, dynamical, and thermal evolution of the protosolar disk material, processes important to understanding how the initial conditions determine the properties of the forming planetary systems (Apai and Lauretta 2009). Here we report evidence for establishing new constraints on the planetesimal formation process from newly available spectral measurements and mineralogical analysis of asteroids and unequilibrated meteorites that distinguish whether a chondrite was formed near the surface or in the interior of a planetesimal. This study illustrates, for the first time, i) that large groups of compositionally similar asteroids (clones) are a natural outcome of planetesimal formation, which direct implication is that meteorites within a given class can originate from several parent bodies ii) that the formation process of the H chondrite parent bodies must have been instantaneous which might be generalized to all planetesimals, and iii) the importance of radial mixing of disk material, the size-sorting of chondrules in particular, on the actual compositional heliocentric gradient among asteroids with LL parent bodies having formed – surprisingly - closer to the Sun than H ones.
24.04.13 (Wednesday)
16:00
"Ionization of the diffuse gas in galaxies"
Christophe MORISSET (IA-UNAM, Mexico)
Abstract
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"Ionization of the diffuse gas in galaxies"

Christophe MORISSET (IA-UNAM, Mexico)

Abstract

Hot low-mass evolved stars at work. We revisit the question of the ionization of the diffuse medium in late type galaxies, by studying NGC 891, the prototype of edge-on spiral galaxies. The most important challenge for the models considered so far was the observed increase of [O iii]Hβ, [O ii]Hβ and [N ii]Hβ with increasing distance to the galactic plane. We propose a scenario based on the expected population of massive OB stars and hot low-mass evolved stars (HOLMES) in this galaxy to explain this observational fact. In the framework of this scenario we construct a finely meshed grid of photoionization models. For each value of the galactic latitude z we look for the models which simultaneously fit the observed values of the [O iii]Hβ, [O ii]Hβ and [N ii]Hβ ratios. For each value of z we find a range of solutions which depends on the value of the oxygen abundance. The models which fit the observations indicate a systematic decrease of the electron density with increasing z. They become dominated by the HOLMES with increasing z only when restricting to solar oxygen abundance models, which argues that the metallicity above the galactic plane should be close to solar. They also indicate that N/O increases with increasing z.
30.04.13 (Tuesday)
12:00
"Atmospheric characterisation of exoplanets: towards terrestrial planets"
David EHRENREICH (U. de Geneve)
Abstract
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"Atmospheric characterisation of exoplanets: towards terrestrial planets"

David EHRENREICH (U. de Geneve)

Abstract

Spectroscopy of exoplanetary transits is our most powerful tool to characterize the atmospheric structure and composition of exoplanets. For the last 10 years, this technique provided a wealth of new insights on the atmospheres of irradiated giant planets. It has been recently applied to smaller exoplanets, from hot Neptunes to super-Earths. The atmospheric characterisation of super-Earths is difficult because of their tenuous transit signals, their compact atmospheres, the presence of hazes or clouds, and their uncertain natures: are they rocky, ocean-planets, or sub-neptunes? Observing transits across bright, nearby stars, is the key to solve these difficulties and a major goal of the CHEOPS mission recently selected by ESA. In the light of the recent exciting discoveries of several super-Earths around bright stars, I will present our current attempts to characterize some of these planets from space with the Hubble Space Telescope, and discuss some prospects to tackle the huge challenge that is the atmospheric characterisation of Earth-like planets.

November 2013

5.11.13 (Tuesday)
12:00
"Mapping progenitor characteristics to supernova classes and transient features"
Joe ANDERSON (ESO, Chile)
Abstract
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"Mapping progenitor characteristics to supernova classes and transient features"

Joe ANDERSON (ESO, Chile)

Abstract

Several thousand supernovae (SNe) have now been discovered, with many events having detailed follow-up programs and analysis completed. To understand the origin of these explosions many progenitor scenarios have been suggested, with complementary studies of their systems (e.g. massive stars, WD systems, binaries, etc). However, we are still lacking a one-to-one mapping between the range of possible progenitor systems and observed SNe. This is a key goal of current SN science with many consequences for our understanding of e.g. stellar evolution, and chemical enrichment. In this talk, I will outline several projects which aim to aid in this understanding. Firstly, we have undertaken studies of the stellar populations within nearby galaxies within which SNe are found, and use these to probe differences in the progenitor ages and metallicities of different SN classes. Secondly, we are working on large databases of, in particular hydrogen-rich SN type II light-curves and spectra, with the aim of deriving pre-SN properties. Finally, I will outline the future of such studies, where we can hope to merge both host galaxy and transient behaviour investigations to further understand the SN phenomenon and its diversity.

February 2013

05.02.13 (Tuesday)
12:00
"Cepheids from long-baseline interferometry"
Alexandre GALLENNE (Universidad de Concepcion, Chile)
Abstract
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"Cepheids from long-baseline interferometry"

Alexandre GALLENNE (Universidad de Concepcion, Chile)

Abstract

Cepheid stars are powerful astrophysical laboratories providing fundamental clues for studying the pulsation and evolution of intermediate-mass stars. Studying these stars in binary systems is particularly important for several reasons: 1) the scatter on the Cepheid P-L relation could be reduced if the effect of companions is well known, 2) it could lead to a better understanding of the age and evolution of Cepheids, and 3) it is necessary to estimate the dynamical masses of Cepheids and constrain theoretical models of their pulsation and evolution. However, most of the companions are located too close to the Cepheid (~1–15 mas) to be observed with a 10-meter class telescope. The only way to spatially resolve such systems is to use long-baseline interferometry. Last year we started a unique and long-term interferometric program that aims at detecting and characterizing physical parameters of the companion of some binary Cepheids, using the multi-telescope recombination instruments VLTI/PIONIER and CHARA/MIRC. In this talk, I will present the first and impressive results of our MIRC observations for the Cepheid V1334 Cyg
06.02.13 (Wednesday)
16:00
"The Salty Surfaces of Jupiter’s Trojan Asteroids and Implications for Astrobiology"
Bin YANG (IFA, Hawaii)
Abstract
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"The Salty Surfaces of Jupiter’s Trojan Asteroids and Implications for Astrobiology"

Bin YANG (IFA, Hawaii)

Abstract

With a total mass comparable to the main asteroid belt, the Trojan asteroids are a major feature in the solar system. Their composition hold the key to answering fundamental questions about planetary migration, the late heavy bombardment, and the origin and evolution of transneptunian objects (TNOs). I conducted a dedicated multi-wavelength survey on the Trojans to search for diagnostic features of water ice, organics and hydrated silicates. In addition, I constructed a modified Mie/Hapke hybrid model to understand the surface structure of these objects. My study shows that the Trojan spectra over a wide wavelength range can be consistently explained by ~1wt% silicates and 2-10 wt% highly absorbing material (such as carbon or iron) suspended in a transparent salt matrix. The origin of the salt matrix can be explained by the thermal evolution if Trojans are composed of primitive silicates and water ice upon formation. The heat from the decay of radionuclides melts the sub-surface ice, causing water to flow and mix with soluble materials to form brine below the cold crust. Impact erosion of the primitive crust then exposes the sub-surface brine, which eventually sublimates leaving behind a salt mantle. It is noteworthy that appropriate salts are better known within biology for stabilizing delicate molecular structures fundamental to life's chemistry. The general conditions of water ice, organics and hydrated silicates on Trojans are, in many ways, a close match to classic thinking about the prebiotic chemistry that gave rise to life.
07.02.13 (Thursday)
12:00
"H3+ absorption line survey in the Central parsec of the Galaxy"
Miwa GOTO (Muenchen Observatory)
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"H3+ absorption line survey in the Central parsec of the Galaxy"

Miwa GOTO (Muenchen Observatory)

Abstract

The cosmic-ray ionization rate is an old and new question of astrophysics. It is the rate how often a hydrogen atom or molecule in the ISM is ionized by the hit of a cosmic ray. This obscure number is in fact one of the most powerful influencers that shows up every corners of astronomy. For instance, secondary electrons are the main heat source of the ISM via the collisions with the gas. Ionized gas tied to the magnetic field controls the dynamics of the gas, therefore the timescales of star formation. Ion-neutral reaction is the primary drive of the ISM chemistry, as neutral-neutral reaction is prohibitively slow in the cold temperature. We will present how one can get hold of the cosmic ray ionization rate in the ISM with the spectroscopy of the ion-molecule H3+, and discuss an unexpected connection of H3+ spectroscopy to the dark matter in the central one parsec of the Galaxy.
12.02.13 (Tuesday)
12:00
"Obscured AGN in the golden epoch of galaxy-AGN coevolution: perspectives for IR and mm observations"
Marcella BRUSA (MPE, Germany)
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"Obscured AGN in the golden epoch of galaxy-AGN coevolution: perspectives for IR and mm observations"

Marcella BRUSA (MPE, Germany)

Abstract

Over the last few years, the existence of mutual feedback effects between accreting supermassive black holes powering AGN and star formation in their host galaxies has become evident. As a consequence, the search for, and the characterization of the evolutive and physical properties of (obscured) AGN over a large redshift interval is a key topic of present research in the field of observational cosmology. Significant advances have been obtained in the last ten years thanks to the sizable number of XMM-Newton and Chandra surveys, complemented by multi-wavelength follow-up programs. After a brief review on how and why X-ray surveys are critical in studying and characterizing AGN, I will focus on the most recent results on AGN-galaxy co-evolution and in particular on observed AGN and galaxy properties. I will also present the science cases for observations at longer wavelengths and show how these new observations may be useful to discriminate among different models of AGN triggering towards a better understanding of the co-eval AGN-galaxy growth.
14.02.13 (Thursday)
12:00
" WD0837+185 - A substellar cuckoo?"
Sara CASEWELL (Leicester University, UK)
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"WD0837+185 - A substellar cuckoo?"

Sara CASEWELL (Leicester University, UK)

Abstract

There is a striking and unexplained dearth of brown dwarf companions in close orbits (< 3AU) around stars more massive than the Sun, in stark contrast to the frequency of stellar and planetary companions. Although rare and relatively short-lived, these systems leave detectable evolutionary end points in the form of white dwarf - brown dwarf binaries and these remnants can offer unique insights into the births and deaths of their parent systems. I will present the discovery of a close (orbital separation ~0.006 AU) substellar companion to a massive white dwarf member of the Praesepe star cluster. I will discuss the evolution of this system and examine the various formation scenarios, concluding that the substellar object was most likely to have been captured by the white dwarf progenitor early in the life of the cluster, rather than forming in situ.
20.02.13 (Wednesday)
16:00
" Seismology of Pre-Main-Sequence Stars: This should be easy. Why isn’t it?"
David GUENTHER (Saint Mary’s University, Canada)
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"Seismology of Pre-Main-Sequence Stars: This should be easy. Why isn’t it?"

David GUENTHER (Saint Mary’s University, Canada)

Abstract

Pre-main-sequence stars are chemically simple stars, not yet nuclear burning, that are seismically active when they pass through the delta Scuti instability strip. As such these homogeneous spheres of mainly hydrogen and helium should exhibit an oscillation spectrum that is simple to model. This is not the case. PMS stars present a wide variety of oscillation characteristics that, except for one specific type, have defied straight forward modelling. Allow me to explain.
21.02.13 (Thursday)
12:00
" The evolution of protoplanetary disks in T Tauri binary systems"
Sebastian DAEMGEN (Toronto University, Canada)
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"The evolution of protoplanetary disks in T Tauri binary systems"

Sebastian DAEMGEN (Toronto University, Canada)

Abstract

Binaries are the most common outcome of star formation. The impact of a stellar binary companion on the evolution of a circumstellar disk, however, is complex and largely unknown. Consequently, star and planet formation in binaries may be significantly different than in single stars. In the largest coherent study of the evolution of circumstellar disks around the components of binary stars to date, we observed 52 binaries in the Orion Nebula Cluster and Chamaeleon I star-forming regions with near-infrared photometry and spectroscopy. In this talk I will summarize the findings, e.g. a significant acceleration of disk evolution in the closest binaries with separations <100AU, and give a short outlook of future projects in the field.
25.02.13 (Monday)
12:00
" Constraining the Magnetic Field Strength in Soft X-ray Intermediate Polars"
Seppo KATAJAINEN (Tuorla Observatory, Finland)
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"Constraining the Magnetic Field Strength in Soft X-ray Intermediate Polars"

Seppo KATAJAINEN (Tuorla Observatory, Finland)

Abstract

The evolutionary connection between two subclasses of magnetic of Cataclysmic Variables (CVs), polars and intermediate polars (IPs) is not yet well established. In the former, the spin period of the accreting white dwarf is synchronised with the binary orbital period while in the latter it is not. Soft X-ray IPs are good candidates for progenitors of polars, but their magnetic field strengths are poorly constrained. A big fraction of them are known to be circularly polarized but converting polarized fractions into magnetic field strengths is problematic, so it is still unclear whether they are of comparable magnetic field strength to polars or not. Only a comprehensive polarimetric study of a sample of soft X-ray IPs is able to reveal their magnetic field strengths, by detection of cyclotron emission humps in their optical/IR spectra. Our studies have provided some evidences that some IPs have comparable magnetic field strengths to some polars and can hence evolve from one to the other.
28.02.13 (Thursday)
12:00
" Planets from the Calan-Hertfordshire Extrasolar Planet Search"
James JENKINS (Universidad de Chile)
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"Planets from the Calan-Hertfordshire Extrasolar Planet Search"

James JENKINS (Universidad de Chile)

Abstract

I will introduce some of the recent work being done as part of the Calan-Hertfordshire Extrasolar Planet Search (CHEPS). I will discuss our radial velocity work and methods to extract Keplerian orbits from undersampled data and from low S/N data and then discuss some new planetary systems we have recently discovered.

January 2013

10.01.13 (Thursday)
12:00
"Can we trust CO as a probe of densities and temperatures in molecular clouds?"
Faviola MOLINA (University of Heidelberg, Center of Astronomy, Institute for Theoretical Astrophysics)
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"Can we trust CO as a probe of densities and temperatures in molecular clouds?"
Faviola MOLINA (University of Heidelberg, Center of Astronomy, Institute for Theoretical Astrophysics)

Abstract

I will present the analysis of one numerical simulation as a good example of a typical Galactic molecular cloud in order to help us understand how to interpret temperature and density inferred from the CO line emission map. We find that the kinetic temperature is always underestimated if it is inferred only from the excitation temperature, Tex, from 12CO(1-0) emission line. On the density analysis, we find that CO primarily traces material at high densities. Besides, by considering a fix value of the CO-H2 conversion factor, the 12CO(1-0) emission map underestimates the density (therefore the mass of H2) at low column densities. In this scenario, the total H2 mass of the cloud, inferred from the emission map, is only 60% of the actual mass of the cloud.
17.01.13 (Thursday)
12:00
"Near Infra-Red spectra of small icy bodies in the Solar System"
Florian GOURGEOT (ESO, Chile)
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"Near Infra-Red spectra of small icy bodies in the Solar System"

Florian GOURGEOT (ESO, Chile)

Abstract

The study of the icy-bodies of the outer solar system provides data of paramount importance to understand the mechanisms of planetary accretion and the role of water in planetary evolution. Water itself is the primary ”volatile” encountered in its solid state beyond Jupiter’s snow line. As my "ESO PhD student time" is now almost over, I will present the work I did during these two years : First, I will show new H &K bands spectra of the Uranus’ icy satellite Miranda. This body is probably the most remarkable of all satellites of Uranus, displaying a series of surface features such as faults, craters and large-scale upwelling, remnant of a geologically very active past. The observations were performed first at the Palomar Observatory with the PHARO instrument (Palomar High Angular Resolution Observer) and then at the Mauna Kea Observatory with SpeX instrument based on the IRTF (Infra-Red Telescope Facility). Then, I will also present new observation results of Haumea, one of the biggest TNO (Trans-Neptunian Object). With it being approximately 2000 x 1600 x 1000 km in size, Haumea's extreme elongation makes it unique among known dwarf planets which is linked to a rotational deformation due to its extremely short 3.9-hour rotation period. Although a high bulk density estimated at a range of 2.6 to 3.3 g.cm-3 suggests a more rocky composition than other KBOs, Haumea and its satellites are considered by a crystalline water-ice multiple system (Dumas et al. 2011). Moreover, Haumea has become the second Kuiper Belt Object after Pluto to show observable signs of surface features. Indeed, a region darker and redder than average on the surface of Haumea has been identified (Lacerda, 2010). Our recent results combining data from several epochs from the Very Large Telescope obtained in Near Infra-Red [1.6 to 2.4 μm] with the integral-field spectrograph SINFONI permit us to provides some characteristics about this dark red spot. Finally, I will briefly show some actual results and perspectives on other icy targets like Jovian moons, and interesting results I obtained on laboratory experiments in Grenoble (France) on icy components (such as methanol) to constrain reflectance models used in the study of several icy bodies.
22.01.13 (Tuesday) LECTURE 1
11:00
"Cosmology: CMB and Dark Energy"
Sidney BLUDMAN (University of Pennsylvania, USA / Universidad de Chile)
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"Cosmology: CMB and Dark Energy"

Sidney BLUDMAN (University of Pennsylvania, USA / Universidad de Chile)

Abstract

We will review the history of our universe, the latest CMB observations, and probes of the Dark Energy. The evolution of the Universe and the growth of structure is well fitted by six-parameter of the Concordance Model (LCDM).
23.01.13 (Wednesday) LECTURE 2
11:00
"Cosmological Dark Energy Observations and Theoretical Interpretations"
Sidney BLUDMAN (University of Pennsylvania, USA / Universidad de Chile)
Abstract
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"Cosmological Dark Energy Observations and Theoretical Interpretations"

Sidney BLUDMAN (University of Pennsylvania, USA / Universidad de Chile)

Abstract

Because our Universe is apparently homogeneous, isotropic and spatially flat, it is described in general relativity by an expanding flat Robertson-Walker metric. We will describe how its expansion history has been observed by cosmic luminosity or angular aperture distances measured for the matter-radiation epoch in the CBR, for the acoustic horizon in the baryon oscillations, and for supernova Ia at red-shift z < 2. Parametrization of this expansion history leads to the Concordance Model ACDM for the recently accelerating cosmic expansion, which hopefully will emerge from four-dimensional general relativity models for dark energy or from higher-dimensional models extending general relativity. In any case, revolutionary phenomenological and epistemological conclusions emerge from the recent discovery of the accelerating cosmic expansion.
24.01.13 (Thursday)
12:00
"The Milky Way bulge as probed by microlensed dwarf stars"
Thomas BENSBY (Lund University)
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"The Milky Way bulge as probed by microlensed dwarf stars"

Thomas BENSBY (Lund University)

Abstract

I will present the most recent results from our ongoing VLT/ToO program aimed at observing dwarf stars to trace the chemical evolution of the bulge. The age distribution, metallicity distribution, and the elemental abundance trends show that the bulge is a very complex region in the Galaxy.
29.01.13 (Tuesday)
12:00
"Magnetic Fields in Bok Globules"
Gesa BERTRANG (Universitaet zu Kiel, Germany)
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"Magnetic Fields in Bok Globules"

Gesa BERTRANG (Universitaet zu Kiel, Germany)

Abstract

The influence of magnetic fields on the star-forming process is still an open question, although a very important one. The best environment to study this influence is given in low-mass star-forming regions, called Bok globules. These objects are less effected by other effects like large-scale turbulences. The magnetic field strength and structure in the dense inner of the globules can be determined by observing the polarized reemission of aligned dust grains in the sub-mm. The magnetic field in the outer, less dense parts of the globules can be traced by observing polarized radiation of background stars in the optical or near-IR. Thus, multi-wavelength observations reveal the magnetic field strength and structure across the entire globule. To study the magnetic field in low-mass star formation I make use of both, numerical simulations and observations of aligned dust grains. The numerical simulations are based on a 3D radiative transfer code where the 3D density distribution, dust properties and the 3D magnetic field structure are free parameters and can therefore be fitted to or constrained by observations. The polarimetric observations are carried out in the sub-mm, near-IR and the optical to trace the globules magnetic field on large scales. Combined with the modeling they provide new insights into the role of magnetic fields in the star-forming process.
30.01.13 (Wednesday)
16:00
"Spectropolarimetric Studies of Type Ia SNe "
Alejandro CLOCCHIATTI (P. Universidad Catolica de Chile)
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"Spectropolarimetric Studies of Type Ia SNe "

Alejandro CLOCCHIATTI (P. Universidad Catolica de Chile)

Abstract

During the last few years, our group has collected spectropolarimetric observations of 17 Type Ia SNe, including both normal and peculiar events. In depth study of the database is starting to reveal facts that need to be incorporated into the paradigms we have at hand to understand SNe Ia progenitors and explosions, or creatively interpreted to modify them. I will show preliminary results from the work of my Ph. D. student at Pontificia Universidad Catolica, Paula Zelaya. They include Type Ia SN that display continuum polarization which, almost certainly, is not of interstellar origin, others which, according to probable scenarios of progenitor evolution should not be spherically symmetric, but seem to be, and late time data that contradict our nascent wisdom on how Type Ia polarization signals should evolve with time.