Recent Talks
List of all the talks in the archive, sorted by date.
Abstract
In the local universe, galaxies fall into one of two populations: a star-forming blue cloud and a red sequence lacking star formation. At redshift z ~ 1.5, however, the red sequence has yet to develop. Over the past 9 Gyrs some process has quenched star formation in blue galaxies and caused them to evolve onto the red sequence by fading and/or merging of their stellar populations. While such a transformation may be occurring across the full range of masses, the highest rate of evolution occurs in massive starbursts at the luminous end of the blue cloud. These galaxies are the Luminous Compact Blue Galaxies (LCBGs). In this talk I present preliminary results of a comprehensive multiwavelength survey of LCBGs from z ~ 0 to z ~ 3 we will be carrying out over the next 5 years using several space and ground-based observatories, including the GTC.
Abstract
Due to their orbits, near-Earth asteroids (NEAs) have been considered the most evident parent bodies of meteorites. Dynamical models show that NEAs come primarily from the inner and central parts of the Main Belt (MB), and they reach their orbits by means of gravitational resonances (mainly ?6 and 3:1). This part of the MB is dominated by spectral types S and Q, also the most common spectral types among the NEA population (~60%), and correspond to objects composed of silicates. Their reflectance spectra show very characteristic absorption bands that can be used to infer their mineralogical composition applying different methods of analysis. Those absorption bands are also present in the spectra of the most abundant class of meteorites (~80%), the ordinary chondrites (OC). In order to better understand the connection between MB asteroids, NEAs and OCs, we undertook a spectroscopic survey of asteroids between 2002 and 2007, using the telescopes and instrument facilities of "El Roque de los Muchachos" Observatory, in the Canary Islands. The survey contains visible and near-infrared spectra (0.5 - 2.5 µm) of a total of 105 asteroids. We have applied a method of mineralogical analysis based on spectral parameters to our sample of NEAs, and also to a sample of 91 MBs and 103 OCs obtained from different databases. We have found some significant compositional differences between NEAs, MBs and OCs. The most remarkable one is that NEAs compositionally differ from the whole set of OCs, and show a more olivine-rich composition, similar to what it is found for LL chondrites (only 8% of the falls). This result suggests that S type NEAs are not the immediate precursors of ordinary chondrites, as it was believed. We consider the size of the objects as the key factor to explain this difference. NEAs are km-sized objects, while meteorites are meter tocm sized objects. Combining the information obtained from the dynamical models and the drift in semimajor axis of the smaller objects due to their thermal intertia (Yarkovsky effect), we set out a possible scenario for the formation and the transport routes of NEAs and meteorites that could explain this compositional difference in a plausible way.
Abstract
Of the 342 planets discovered so far orbiting other stars, 58 'transit' the stellar disk, meaning that they can be detected by a periodic decrease in the starlight flux. The light from the star passes through the atmosphere of the planet, and in a few cases the basic atmospheric composition of the planet can be estimated. As we get closer to finding analogues of Earth, an important consideration toward the characterization of exoplanetary atmospheres is what the transmission spectrum of our planet looks like. Here we report the optical and near-infrared transmission spectrum of the Earth, obtained during a lunar eclipse. Some biologically relevant atmospheric features that are weak in the reflected spectrum (such as ozone, molecular oxygen, water, carbon dioxide and methane) are much stronger in the transmission spectrum, and indeed stronger than predicted by modeling. We also find the fingerprints of the Earth's ionosphere and of the major atmospheric constituent, diatomic nitrogen (N2), which are missing in the reflected spectrum. Our results indicate that the technique of transit spectroscopy of rocky planets may be a very powerful tool for exoplanet atmospheric characterization, and is likely to provide the first detection of a habitable exobiosphere.
Abstract
The SAURON survey has revised our view of early type galaxies discovering that central disks and multiple kinematic components are common; 75% of the sample have extended ionized gas, often misaligned with the stars; half of S0s and 25% of Es have intermediate age populations. There is a tight relationship between the escape velocity and Mg line strength which holds both within and between galaxies raising uncomfortable questions for hierarchical assembly. Many of the properties of ETGs are related to a measure of their specific angular momentum : slow rotators are triaxial, close to spherical, isotropic and frequently exhibit decoupled central kinematics, whereas fast rotators are intrinsically flatter, oblate, have disk-like (anisotropic) kinematics and often have Mg enhanced disks. In general the slow rotators are more massive and have older populations Only half of the elliptical galaxies exhibit slow rotation, the remainder have stellar disks showing that the historic division by morphological class is physically misleading. We suggest that the contrasting physical properties of fast and slow rotators arise through distinct assembly histories with slow rotators forming in gas free, dry mergers and fast rotators retaining a disk component through a dissipative merger.
Abstract
Long gamma-ray bursts are supposed to be connected to the death of very massive stars. Due to their brightness, we can detect them to much larger distances than supernovae. Using them as powerful lightsources, they allow us to study star-forming high redshift galaxies and their interstellar medium in great detail with medium and high resolution spectroscopy. Despite the large redshift ranged spanned by GRBs, there is surprisingly little evolution in the properties of their host galaxies which might indicate that GRBs can only occur under certain conditions. This can be investigated from a few bursts at very low redshifts where we can resolve their host galaxies e.g. with integral field spectroscopy. The immediate surroundings might allow us some conclusions on the progenitors of GRBs.
Abstract
Observations have shown that massive galaxies at high redshift have much smaller sizes than galaxies of similar mass today. The mean stellar density of such objects was almost two orders of magnitude higher than the ones we measured in the most massive nearby galaxies, reaching, in some cases, densities similar to those observed in globular clusters. What is the nature of these objects? And, how these objects have been transformed into the present population of massive galaxies? We will summarize the recent findings our group has done on this topic. In particular, we will focus on our search for finding relics of these compact galaxies in the nearby universe, and the effort we have done for measuring the evolution of the velocity dispersion of these galaxies in the last 10 Gyr. The implications of this research within the galaxy formation scenario will be discussed.
Abstract
In the next decade astronomers will attempt to constrain the nature of dark matter, dark energy and the (perhaps inflationary) processes which generated structure as well as understanding the astrophysics of galaxy evolution and the formation and evolution of our Milky Way and Local Group. Large-scale spectroscopic surveys on large telescopes will be critical to achieving reliable results in all these areas. The desideratum is a survey which obtains the spectra of a few times 105 galaxies from the visible into the near IR at each of a sufficient number of redshift slices that one can follow the evolution of all interesting populations. Large samples of different stellar populations in different Local Group environments will also be targeted. I will summarize the outline of a multi-object 0.4-1.7 μ spectrograph for GTC and discuss the status of miniSIDE. MiniSIDE has been conceived as a pathfinder for a large fiber-fed survey spectrograph but will be a scientific instrument on its own, capable of providing high quality science data and be competitive within the instrumentation suite of GTC. A Letter of Intent has been submitted recently to propose miniSIDE as a facility science instrument for GTC.
Abstract
R is one of the software packages with the shortest name, but with the largest array of capabilities. It is a language and environment for statistical computing and graphics, and provides a wide variety of statistical (linear and nonlinear modelling, classical statistical tests, time-series analysis, classification, clustering, ...) and graphical techniques. One of R's strengths is the ease with which well-designed publication-quality plots can be produced, including mathematical symbols and formulae where needed. In this talk, Sebastien will give a short introduction to R, and will show us how his own research has benefited from it.
Abstract
CanariCam es un instrumento que trabajará en el rango del infrarrojo medio y que hará imagen, espectroscopía, polarimetría y coronografía. Está previsto que su puesta a punto en el GTC comience en breve. La intención de este workshop es ayudar a la comunidad a familiarizarse con el tipo de ciencia que puede hacerse en el infrarrojo medio con un instrumento como CanariCam.La observación en el infrarrojo medio es una técnica poco conocida para la mayor parte de la comunidad de usuarios del GTC, pero actualmente las observaciones en este rango son ya rutinarias. Especialmente en la banda de 10 μ, donde la transparencia del cielo es bastante estable, es posible observar en el infrarrojo medio con la seguridad de que pueden obtenerse datos de calidad siguiendo procesos bastante rutinarios.
CanariCam será el instrumento de infrarrojo medio más avanzado instalado en un gran telescopio. Durante la reunión, se discutirán las capacidades de CanariCam. La mayor parte del workshop se centrará en las charlas de los conferenciantes que mostrarán las múltiples facetas de las aplicaciones científicas en el infrarrojo medio. A la vez, se anima a los participantes a presentar contribuciones que traten (en su mayor parte, aunque no en exclusiva), temas no abordados por los conferenciantes invitados.
Conferenciantes invitados: Charlie Telesco: CanariCam Overview Humberto Campins: Cometary Science Javier Licandro: TNOs Rafael Rebolo; Substellar Objects David Barrado: Proto-Stellar Objects Nuria Huélamo: Disks & T Tauri stars Jim Hough: The ISM & Star formation (Polarimetry) Arturo Manchado: PAHs, AGBs & Proto-Planetaries Paco Najarro: Obscured Star Clusters Pepa Masegosa: LINERs Almudena Alonso; Ultraluminous Galaxies Chris Packham: AGN Nancy Levenson: Dusty Tori Ismael Pérez Fournón: Synergies with Herschel
Abstract
CanariCam es un instrumento que trabajará en el rango del infrarrojo medio y que hará imagen, espectroscopía, polarimetría y coronografía. Está previsto que su puesta a punto en el GTC comience en breve. La intención de este workshop es ayudar a la comunidad a familiarizarse con el tipo de ciencia que puede hacerse en el infrarrojo medio con un instrumento como CanariCam.La observación en el infrarrojo medio es una técnica poco conocida para la mayor parte de la comunidad de usuarios del GTC, pero actualmente las observaciones en este rango son ya rutinarias. Especialmente en la banda de 10 μ, donde la transparencia del cielo es bastante estable, es posible observar en el infrarrojo medio con la seguridad de que pueden obtenerse datos de calidad siguiendo procesos bastante rutinarios.
CanariCam será el instrumento de infrarrojo medio más avanzado instalado en un gran telescopio. Durante la reunión, se discutirán las capacidades de CanariCam. La mayor parte del workshop se centrará en las charlas de los conferenciantes que mostrarán las múltiples facetas de las aplicaciones científicas en el infrarrojo medio. A la vez, se anima a los participantes a presentar contribuciones que traten (en su mayor parte, aunque no en exclusiva), temas no abordados por los conferenciantes invitados.
Conferenciantes invitados: Charlie Telesco: CanariCam Overview Humberto Campins: Cometary Science Javier Licandro: TNOs Rafael Rebolo; Substellar Objects David Barrado: Proto-Stellar Objects Nuria Huélamo: Disks & T Tauri stars Jim Hough: The ISM & Star formation (Polarimetry) Arturo Manchado: PAHs, AGBs & Proto-Planetaries Paco Najarro: Obscured Star Clusters Pepa Masegosa: LINERs Almudena Alonso; Ultraluminous Galaxies Chris Packham: AGN Nancy Levenson: Dusty Tori Ismael Pérez Fournón: Synergies with Herschel
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