Recent Talks

The fate of ionizing radiation from massive stars has fundamental consequences on scales ranging from the physics of circumstellar disks to the ionization state of the entire universe. On galactic scales, the radiative feedback from massive stars is a major driver for the energetics and phase balance of the interstellar medium in star-forming galaxies. While even starburst galaxies appear to be largely optically thick in the Lyman continuum, ionization-parameter mapping shows that significant populations of HII regions within galaxies are optically thin, powering the diffuse, warm ionized medium. I will discuss our multi-faceted work to clarify our understanding of radiative feedback in star-forming galaxies from the Magellanic Clouds to starbursts.

In this talk we will show the evolution of high-redshift (z≥ 1.4) quiescent galaxies in the COSMOS field. We have studied an IRAC (mag 3.6 μm < 22.0) selected sample of ~ 18 000 galaxies at z≥ 1.4 in the COSMOS field with multiwavelength coverage extending from the U band to the Spitzer 24 μm one. We have derived accurate photometric redshifts and other important physical parameters [masses, ages and star formation rates (SFR)] through a SED-fitting procedure. Galaxies have been divided according to their star formation activity into actively star-forming, intermediate and quiescent galaxies depending on their specific star formation rate (sSFR = SFR/M). The evolution of the Galaxy Stellar Mass Funtion (GSMF) of the different populations, in particular of the quiescent galaxies, has been investigated in detail. There is a significant evolution of the quiescent stellar mass function from 2.5 < z < 3.0 to 1.4 < z < 1.6, increasing by ~1 dex in this redshift interval. We find that z ~1.5 is an epoch of transition of the GSMF: while the GSMF at z≳ 1.5 is dominated by the star-forming galaxies at all stellar masses, at z≲ 1.5 the contribution to the total GSMF of the quiescent galaxies is significant and becomes higher than that of the star-forming population for M≥ 1010.75 Msun. We derive the fraction of quiescent/star-forming galaxies with redshift, as well as the stellar mass density. We also compare our results with the predictions of theoretical models. Finally, I will introduce my current project: studying in deeper detail the IRAC drop-outs of the sample with new nIR (ULTRA-VISTA) and fIR (Herschel) data to elucidate between very dust-obscured objects or high-z star forming galaxies, which could help us to put some constrains to the high-mass end of the GSMF at high-z.

Spectroscopic observations of stars do not only provide us with valuable information about the stars themselves, but over the last years such observations have lead to numerous exoplanet discoveries and new insights into planet formation. One important clue emerged at the dawn of the field: the existence of hot Jupiters, gas giants with orbital distances much smaller than an astronomical unit. We and other groups found some of these planets orbiting their stars on highly inclined or even retrograde orbits. I show how the orientation of the stellar axis in relation to the orbital plane (obliquity) reveals the mechanism by which these planets move inwards. Similar measurements in multiple transiting planet systems, with smaller planets will further enhance our understanding of the formation and evolution of planetary systems. In order to take those measurements we need to improve the way we analyze spectra. I present recent results obtained with such a new technique. These include multiple planet systems and results from my "BANANA" survey of close binaries, some of which, such as DI Herculis, also show strong misalignment. The same technique will allow for a reduction of stellar noise in radial velocity surveys, improving our ability to search for smaller, more Earth like planets around bright nearby stars.

El CVN es un formato estándar de Currículum Vitae desarrollado por el Ministerio de Economía y Competitividad (MINECO <http://www.mineco.es/>) a través de la Fundación Española para la Ciencia y la Tecnología (FECYT <http://www.fecyt.es/>) cuyo objetivo es el de normalizar los CVs de investigadores. Este formato está ampliamente soportado en centenares de entidades como ministerios, universidades y otras OPIs, fundaciones, agencias, etc... Entidades como la ANECA están adaptando sus sistemas al CVN y en la actualidad es el formato de CV recomendado (y probablemente el único que se aceptará próximamente) en convocatorias del Plan Nacional de I+D+iy otras similares

Por tanto, existen indudables ventajas en adoptar el estándar CVN como formato curricular. Además, el Área de Investigación se está planteando construir su base de datos curricular a partir del estándar CVN y podría contribuir a facilitar el mantenimiento de los currículos. Todo esto se comentará en la charla.

En este seminario se dará una visión general de este proyecto y se enfocará a las necesidades específicas del personal del IAC. Para ello y mediante ejemplos se explicará cómo obtener su CVN a partir de un CV existente en formato CICYT, MICINN o Ramón y Cajal en unos simples pasos, así como utilizar información de bases de datos como ADS y otras fuentes para mantenerlo actualizado.

In recent years accurate photometric and spectroscopic observations have
provided sound evidence that Galactic Globular Clusters can not be longer
considered the prototype of Simple Stellar Populations. In this talk we
present the most recent updates concerning the empirical evidence and
discuss the theoretical framework required for interpreting observations.
Current shortcomings in the interpretation of how the multiple stellar
populations formed in a given cluster are also discussed.

The effects that environment produce on galaxy disks and how they modify the subsequent formation of bars need to be distinguished to fully understand the relationship between bars and environment. To shed light on this issue, we derive the bar fraction in three different environments ranging from the field to Virgo and Coma Clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of galaxy luminosity (and mass) in the field and Coma Cluster is statistically significant, with Virgo being an intermediate case. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies, the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on environment could be resolved by taking into account the different luminosity ranges probed by the galaxy samples studied so far.

Morphologies of star-forming galaxies at z>1 are typically irregular containing a handful of dominant bright regions. Recent observational evidence suggest that many of these galaxies are governed by disc-like rotation. Using Halpha galaxy kinematics from OSIRIS+LGSAO we find that within z~1 turbulent discs star-forming regions have average sizes of 1.5 kpc and average Jeans masses of 4.2x10^9 \Msun, in total accounting for 20-30% of the stellar mass of the discs. These findings lend observational support to models that predict larger star-forming regions will form as a result of higher disc velocity dispersions driven-up by cosmological gas accretion.  As a consequence of the changes in global environment, it may be predicted that star-forming regions at high redshift should not resemble star-forming regions locally. Yet despite the increased sizes and dispersions, high-z star-forming regions and HII regions are found to follow tight scaling relations over the range z=0-2 for Halpha size, velocity dispersion, luminosity and mass when comparing >2000 HII regions locally and 30 regions at z>1.  While the turbulence of discs may have important implications for the size and luminosity of regions which form within them, the same processes likely govern their formation from high redshift to the current epoch. We are now able to test this conclusion with first results from a new sample of z=0.1-0.2 highly star-forming turbulent galaxies from the Sloan Digital Sky Survey.

Observational studies show that voids are prominent features of the large scale structure of the present day Universe. Even though their emerging from the primordial density perturbations and evolutionary patterns differ from dark matter halos, N-body simulations and theoretical models have shown that voids also merge together to form large void structures. In this study, progressing from previous works, we formulate a toy model to construct a merger tree algorithm of isolated spherical voids by adopting the halo merging algorithm given by Lacey and Cole (1993) in the Einstein de Sitter (EdS) universe. To do this, we take into account the general mass distribution of voids which consists of two main void sociologies: merging and collapsing. We show that the mass distribution function can be reduced to a simple form by neglecting the collapse void contribution. As a result of this, the void mass fraction has a contribution only from isolated gradually merging voids. This algorithm becomes the analogue of the halo merging algorithm. Based on this isolated spherical void distribution, we obtain the void merging algorithm, void merging rate and void survival times in terms of the self similar and standard cold dark matter models in the EdS universe.

The Southeastern Association for Research in Astronomy (SARA) is a consortium of 11 US universities that currently remotely operates a 0.9 m telescope at Kitt Peak National Observatory and a 0.6 m telescope at Cerro Tololo Inter-American Observatory. Collectively, the SARA institutes predominantly use differential photometry techniques for studies ranging in scale from solar system asteroids and minor planets, to transiting exo-planets, most types of variable stars and binaries, to active galactic nuclei and blazers. In addition, the SARA telescopes are frequently used in preliminary observations for other major observatories (HST, for example). In this talk a brief history and the philosophy of SARA will be given, as well as more details on the current types of scientific programs run by the SARA institutes. The new scientific opportunities enabled by the JKT will also be highlighted. Finally, our development and funding plans will be presented. A description of the telescope automat ion process by Astronomical Consultants & Equipment, Inc. will conclude.

This talk will give an overview of our understanding of the Sun in the 1960's, the major discoveries since then, and the main questions that need to be answered in future. It will focus on the role of the magnetic field in the solar interior, the photosphere, prominences, coronal heating and eruptive flares.