Seminars and Colloquia at ESO/Santiago

For ESO and ESO-related Conferences and Workshops in Europe and Chile please check the main Conferences and Workshops page.


Broadcast of the ESO talks is available upon request.  If anyone is interested, kindly contact us via email
at least 30 min prior  to the beginning of the talk.


February 2016

9.02.16 (Tuesday)
12:00
"Narrow band observations with wide field imagers. A scientific perspective"
Alessandro EDEROCLITE (CEFCA)
Abstract
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"Narrow band observations with wide field imagers. A scientific perspective"

Alessandro EDEROCLITE (CEFCA)

Abstract

Wide-field imagers are playing a crucial role in modern astrophysics, nevertheless, most wide-field surveys are performed in white light or broad band filters (with some relevant exceptions). The Observatorio Astrofísico de Javalambre has been designed to carry out the Javalambre Physics of the accelerating universe Astrophysical Survey (J-PAS), which consists of 8,500sq.deg. of the northern extragalactic sky observed in 59 filters with the main aim to detect baryonic acoustic oscillations to be used as cosmological indicators. The photometric calibration will be based on another project (involving 12 filters): the Javalambre Photometry of the Local Universe Survey (J-PLUS). In this talk, I will review the scientific potential of these surveys and emphasise the possibilities opened by OAJ to European astronomy.

10.02.16 (Wednesday)
15:30
"Mass-loss process of evolved AGB stars at high angular resolution"
Claudia PALADINI (Université Libre de Bruxelles)
Abstract
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"Mass-loss process of evolved AGB stars at high angular resolution"

Claudia PALADINI (Université Libre de Bruxelles)

Abstract

The mass-loss process from evolved stars is a key ingredient for our understanding of many fields of astrophysics, including stellar evolution and the chemical enrichment of the interstellar medium via stellar yields. How the mass loss affects the atmosphere of late-type stars, particularly asymptotic giant branch (AGB) stars, is still argument of discussion since the 70's. The standard model pictures the AGB stars being round with a spherically symmetric stellar wind. However this is in contrast with observations of post-AGB and planetary nebulae. Taking advantage of the recent results of the Herschel mass loss of Evolved StarS (MESS) program, we initiated a coordinated effort to study the same sample of AGB stars with different techniques. Our aim is to characterise the geometry of the mass-loss process in AGB stars at different spatial scales. In this contribution I will give an overview of the recent advances from infrared interferometry in unveiling surface structures on the photosphere of giant. I will then move to the dust forming region in the mid-infrared presenting the results of our VLTI/MIDI Large program. I will conclude highlighting how our field of research will benefit from the synergy of the current interferometric instrument(s) with the second generation VLTI facilities GRAVITY and MATISSE.

11.02.16 (Thursday)
11:00
"AGN feedback through winds and turbulence across cosmic time" (Joint ESO-ALMA colloquium)
Nicole NESVADBA (Institut d'Astrophysique Spatiale in Orsay)
Abstract
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"AGN feedback through winds and turbulence across cosmic time" (Joint ESO-ALMA colloquium)

Nicole NESVADBA (Institut d'Astrophysique Spatiale in Orsay)

Abstract

Substantial observational and theoretical progress in the last decade has left little doubt that supermassive black holes, which seem to be near-ubiquitous in the nuclei of galaxies, play a significant role in shaping the properties of their host galaxies. AGN emit more than the binding energy of a massive galaxy in a single activity period, which makes them attractive candidates to limit star formation even in very massive galaxies. In spite of encouraging recent progress, however, our understanding of how AGN feedback works is still very limited. Most modelers and observers equate feedback with winds, but several observations in recent years have shown that turbulence might be another important way through which AGN interact with their environment. I will report on our on-going efforts to quantify the impact of winds and turbulence on the warm ionized and molecular gas in powerful radio-selected AGN with VLT/SINFONI and other instruments. Through continuous efforts since SINFONI's first run as a guest instrument on the VLT in 2003, we have been studying radio-selected AGN spanning 3 orders of magnitude in radio power, collecting a sample of about 50 sources with deep imaging spectroscopy. We find that the most powerful high-redshift AGN indeed drive out large fractions of their ISM in form of winds as postulated, with significant differences between AGN with and without prominent radio source. Towards lower radio power, turbulence seems to play an increasingly important role. I will discuss how winds and turbulence together may be sufficient to 'quench' the main formation phase of massive galaxies at high redshift, and 'maintain' low gas fractions and star formation rates over long cosmic times. I will also illustrate how turbulence alone may inhibit the formation of gravitationally bound clouds and subsequent star formation, as a first step towards understanding how AGN 'feed back' within the general framework of turbulence-regulated star formation in galaxies.

25.02.16 (Thursday)
12:00
"A pragmatic Bayesian perspective on correlation analysis: The exoplanetary gravity - stellar activity case"
Pedro FIGUEIRA (University of Porto)
Abstract
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"A pragmatic Bayesian perspective on correlation analysis: The exoplanetary gravity - stellar activity case"

Pedro FIGUEIRA (University of Porto)

Abstract

Very often we want to assess the if there is a correlation between two quantities. This is often done in the frequentist framework, using p-value analysis; unfortunately, it has been demonstrated that there are some fundamental flaws behind this kind of null hypothesis testing procedure. We consider the alternative approach of applying the Bayesian framework. To do so, we estimate the probability distribution of the parameter of interest, $\rho$, characterizing the strength of the correlation. We provide an implementation of these ideas and concepts using python programming language and the pyMC module in a very short (~130 lines of code, heavily commented) and user-friendly program. We used this tool to assess the presence and properties of the correlation between planetary surface gravity and stellar activity level as measured by the log(R'_HK) indicator. The results of the Bayesian analysis are qualitatively similar to those obtained via p-value analysis, and support the presence of a correlation in the data. The results are more robust in their derivation and more informative, revealing interesting features such as asymmetric posterior distributions or markedly different credible intervals, and allowing for a deeper exploration. We encourage those interested in this kind of problem to apply our code to his/her own scientific problems. The full understanding of what the Bayesian framework is can only be gained through the insight that comes by handling priors, assessing the convergence of Monte Carlo runs, and a multitude of other practical problems. We hope to contribute so that Bayesian analysis becomes a tool in the toolkit of researchers, and they understand by experience its advantages and limitations.


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