Latest talks

List of all the talks in the archive, sorted by date.



Monday September 18, 2017
Dr. Martín Crocce
Institute for Space Science, Barcelona, Spain


Monday September 18, 2017
Dr. Diego Blas
CERN, Switzerland


Monday September 18, 2017
Prof. Yun Wang
California Institute of Technology, USA


Tuesday September 12, 2017
Dr. Monika Lendl
Austrian Academy of Sciences, Space Research Institute


Planetary transits have proven to be one of the most efficient means of finding planets outside the Solar system, counting over 2500 exoplanet discoveries. These transiting planets are paramount for the study of exoplanet atmospheres as the stellar light is filtered through the planetary atmosphere during transit and planetary absorption signatures become imprinted on the stellar spectrum. Observations of hot-Jupiter transmission spectra have become increasingly numerous and reliable throughout recent years, allowing detailed constrains on the planet's physical and chemical atmospheric properties, interactions between planet and host star, and planet formation history. While early work relied largely on space-based facilities, ground-based techniques have seen major advances recently and have become instrumental in performing an extensive and comparative study of exoplanet atmospheres. I will review the current state of knowledge, summarize recent results and discuss future prospects of exoplanet characterization, with a focus on the potential of ground-based facilities. In particular, I will present recent and new results by our team on the transmission spectra of hot Jupiters.

Thursday August 24, 2017
Dr. Sébastien Comerón
University of Oulu, Finland


The reports of thick discs' death are greatly exaggerated: Thick discs are NOT artefacts caused by diffuse scattered light

Recent studies have made the community aware of the importance of accounting for scattered light when examining low surface brightness galaxy features such as thick discs. In past studies on thick discs of edge-on galaxies the point spread function (PSF) effects were not taken into account or were modelled with a Gaussian kernel.

We have re-examined results on photometric decompositions of discs in the Spitzer Survey of Stellar Structure of Galaxies (S4G) using a revised PSF model that accounts for extended wings out to more than 2.5 arcminutes. We study 141 edge-on galaxies, so we more than double the samples examined in past studies. This is the largest sample of extragalactic thick discs studied so far.

The main difference between our current fits and those presented in the past is that now the scattered light from the thin disc dominates the surface brightness at levels below 26 mag arcsec-2. This change, however, does not affect drastically any of our previously presented results: 

- Thick discs are nearly ubiquitous. They are not an artefact caused by scattered light as has been suggested elsewhere. 
- Thick discs have masses comparable to those of thin discs in low-mass galaxies (with circular velocities v_c<120 km s-2) whereas they are typically less massive than the thin discs in high-mass galaxies.
- Thick discs and central mass concentrations seem to have formed at the same epoch from a common material reservoir.
- Approximately sixty per cent of the up-bending breaks in face-on galaxies are caused by the superposition of a thin and a thick disc where the scale-length of the latter is the largest.

Friday July 14, 2017
Prof. David Nidever


How galaxies form and evolve remains one of the cornerstone questions in our understanding of the universe on grand scales.  While much progress has been made by studying galaxy populations out to high redshifts, there is also much to be learned from near-field cosmology ? that is, investigating nearby galaxies in detail using observations of resolved stars.  I will highlight some recent results from several projects that are providing new insights into the structure and formation history of the Milky Way and the Magellanic Clouds.  First, I will discuss how I am mapping the stellar halos of the Milky Way and the Magellanic Clouds and thereby uncovering clues to their hierarchical buildup.  Second, I will summarize results from the APOGEE survey that, in combination with high-resolution simulations, are revealing the chemical structure, evolution and dynamical history of the Milky Way disk.  I will end with a brief summary of my recent work with the NOAO Data Lab to create an all-sky catalog of NOAO archive images (the NOAO Source Catalog or NSC).

Wednesday July 12, 2017
Dr. Carlos Hernández Monteagudo


The Javalambre Photometric Local Universe Survey (aka J-PLUS) has covered almost 500 square degrees since it started operations in November 2015. J-PLUS is conducted by the 80-cm diameter Javalambre Auxiliary Survey Telescope (JAST/T80), which, despite its modest size, has a relatively large Field of View (~2 square degrees). The camera attached to JAST/T80 counts with a system of five broad band filters (u_JAVA, g_SDSS, r_SDSS, i_SDSS, z_SDSS) plus seven narrow band filters (of width ranging from 10 to 20 nm). Four of these narrow band filters are centered upon Halpha, Hdelta, Ca Triplet, and OII 3727A (rest frame).  After a strategic redefinition of  filter depths, JAST/T80 should cover the Javalambre sky at a speed of 1500 square degrees per year. I will briefly describe the instrument and the survey specifications, together with some of the scientific projects under development, and their preliminary results. I will also describe the J-PLUS online data base in an attempt to encourage members and potential members of the collaboration to exploit these data.

Thursday June 29, 2017
Prof. Ellen Zweibel
Univ. Wisconsin-Madison


Star formation and supermassive black hole growth in galaxies appear to be self limiting. The mechanisms for self regulation are known as /feedback/. Cosmic rays, the relativistic particle component in interstellar and intergalactic plasma, are among the agents of feedback. Because cosmic rays are virtually collisionless in the plasma environments of interest, their interaction with the ambient medium is primarily mediated by large scale magnetic fields and kinetic scale plasma waves. Because kinetic scales are much smaller than global scales, this interaction is most conveniently described by fluid models. In this paper I discuss the kinetic theory and the classical theory of cosmic ray hydrodynamics (CCRH) which follows from assuming cosmic rays interact only with self excited waves. I generalize CCRH to generalized cosmic ray hydrodynamics (GCRH), which accommodates interactions with extrinsic turbulence, present examples of cosmic ray feedback in galaxies and galaxy clusters, and assess where progress is needed.

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