Recent Talks

On February 15, while we were preparing to observe the close approach of the potentially hazardous asteroid (PHA) 2012 DA14 another small asteroid entered the Earth’s atmosphere over Russia. The object, of about 17m in diameter and  11.000 tons exploded in the atmosphere generating a bright flash, a powerful shock wave and small fragmentary meteorites. About 1500 people were injured because of the shock wave effects in the city of Chelyabinsk located east of the Ural Mountains and on the border of Europe and Asia. The more than 400 kilotons released suggest that this was largest asteroid that entered the Earth atmosphere since the 1908 Tunguska event.

The differences between the orbits of DA14 and the asteroid that caused the Chelyabinsk event showed that both objects are not related. The composition of the meteorite and the spectrum of DA14 we obtained with the GTC also support that.

In this talk I will resume all the information about the Chelyabinsk event and discuss the relevance of studying the near-Earth asteroids, in particular the PHAs, and present the main results of our study of asteroid DA14 (de León et al. 2013). I will also discuss the relevance of space mission studies on this objects and resume our participation in MarcoPolo-R and AIDA missions. 

Evolution of galaxies is relatively well known up to z ~ 5, but beyond this limit and regarding the few number of galaxies confirmed by spectroscopy, their evolution is still uncertain. In the last five years, many projects and instruments aiming at pushing the limits of the Universe have emerged. Among them, the WIRCam Ultra Deep Survey (WUDS), a very large (~400 arcmin^2 field of view) and deep (m_H=27.00 AB) survey covering wavelength from Y to Ks bands, dedicated to select the brightest sources at z > 4.5, has just been finished.This survey takes benefit from the deep images from the CFHT-LS (Groth Strip) in u, g, r, i and z-band to improve the wavelength coverage and thus the determination of photometric redshift in each sample. The evolution of galaxies has been studied through the evolution of the UV Luminosity Function from z~5 up to z~9. During this talk I will present you the WIRCam Ultra Deep Survey and the most popular method used to select the very high-redshift sources. Then I will focus on the determination of the luminosity function and on the implications of this evolution on the Epoch of Reionization. I will finish this presentation by giving some perspectives, and especially the results that we can expected from futures instruments and telescopes (e.g. EMIR @ GTC, KMOS and MUSE @ VLT, JWST, E-ELT).

Segunda charla que ofrecemos a todo el personal del IAC para su 
posterior uso en charlas de divulgación. En este caso se trata de una 
charla para público adulto o jóvenes de secundaria o bachillerato.
Puede adaptarse fácilmente según audiencia. El material quedará
de libre acceso para todos los interesados. NO HABRÁ DIBUJOS ANIMADOS.
Es una charla sencilla en la que lo que cuenta es lo que se cuenta...
Ven, sorpréndete (y cuéntalo!)

The CoRoT space mission aims at detecting planets with the transit method. In operation for more than 6 years, the instrument has monitored a couple of ten fields located in two opposite directions the Galactic plane for durations up to about 160 days. Transits are detected in about 100 up to 300 light curves per run. The large majority of them are however pinpointed as transiting stellar systems thanks to the identification of secondary eclipses or light curve modulation. The nature of the remaining candidates is then assessed through a multi-step strategy of complementary observations. This approach has allowed the discovery of a variety of planets with a large range of properties, from the first Super-Earth, CoRoT-7b to CoRoT-9b, the first temperate hot Jupiter or even the two transiting companions in the theoretical mass domain of brown dwarfs. We will review the status of the mission and then present the CoRoT exoplanetary systems and their properties.

The stellar spectroscopic sequence has now been extended into very cool objects bridging the gap between low-mass stars and classical planets. Those objects, called Y dwarfs, are the coolest substellar objects known to date with temperatures below 500 Kelvins. We obtained z-band far-red imaging for six Y dwarfs and a T9+Y0 binary with GTC/OSIRIS to characterise their spectral energy distribution. This photometric dataset represent the first optical detection of Y dwarfs. I will present the z-band photometry, optical-to-infrared colours, and proper motions of these Y dwarfs. I will discuss the larger dispersion in the optical-to-infrared colours of Y dwarfs than in warmer brown dwarfs, which may originate from presence of sulfide clouds, the depletion of alcalines, and/or gravity effects.

X-ray transients are binary systems composed by a 'normal' star which is transfering mass onto a compact object (either a black hole or a neutron star) through Roche lobe overflow. These systems show sporadic outburst episodes and long quiescence states, being ideal systems to search for stellar-mass black holes. Different studies predict a Galactic population of ~10^3-10^4 X-ray transients, however, there are only 18 stellar-mass black holes dynamically confirmed (and other ~32 candidates whichc share similar timing and spectral properties).

In this talk I'll present the case of Swift J1357.2-0933, a new X-ray transient discovered in 2011. Our analysis shows that Swift J1357.2-0933 is the first black hole transient seen at a large inclination (>75º). High time resolution lightcurves show dips or eclipses produced by a vertical structure present in the inner accretion rather than the companion star. Some dips display up to ~50% reduction of flux in ~2min (~30% reduction of flux in 7s). Moreover, the dips present a recurrence period of a few minutes which increases with time. This can only be explained by the expansion of the obscuring structure outward in the accretion. Swift J1357.2-0933 could be the prototype of an hytherto Galactic population of black hole transients with large inclinations.

This has been an exciting year for the SDSS-III collaboration. BOSS has made spectacular progress and it is running 6 months ahead of schedule. APOGEE has secured ~ 300,000 spectra for 50,000 stars, mostly red giants and nearly half of its total sample. The APOGEE Stellar Parameter and Chemical Abundance Pipeline is providing reliable atmospheric parameters, including metallicities. Data Release 10 (DR10) will take place next summer, but DR10 BOSS data are already available to the collaboration, and DR10 APOGEE data products will be internally released in the next few weeks. SDSS activity is growing at the IAC. We will report on SDSS-III news and SDSS-IV prospects, including an overview of the SDSS-IV programs APOGEE-2, eBOSS (+TDSS+SPIDERS), and MaNGA.

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.