Recent Talks

Cognitive Astrophysics brings together tools, techniques and lessons learned from fields apparently as far apart as linguistics, philosophy and cognitive psychology, and merges them with modes and methods of understanding and discovery in modern cosmology, galaxy evolution and astrophysics. I will present an illustrated overview of the field from a variety of perspectives, and close with a discussion of "Pentessence" as an example of a globally organizing concept describing self-gravitating systems known to be operating on vastly different physical scales and in apparently disparate astrophysical circumstances.

At the end of 2013, the Hubble Space Telescope has started its last flagship program : the "Frontier Fields". In the framework of this project, three of the most powerful space telescopes to date - Hubble, Spitzer and Chandra - will dedicate a large amount of their observing time to observe six galaxies clusters, who act as additional lenses and amplify the light from background sources, including very faint galaxies to the edge of the observable Universe. These images will reach a depth comparable to the "Hubble Ultra Deep Field", but in a cluster field. Abell 2744, the first Frontier Fields target, has been observed by HST since November 1 and the first release has been made public on December 17. We have used this dataset to search for Lyman Break galaxy (LBG) at z>6.5 in the 4.9 arcmin^2 field of view of the WFC3. Several sources have been selected and the highest redshift object is estimated at z=8, called Abell2744_Y1. The amplification factor of this object is relatively modest (mu=1.5). We used our own reduced Spitzer images at 3.6 and 4.5 microns to constrain the Spectral Energy Distribution (SED) of the z=8 galaxy candidate. We computed its properties by SED-fitting using templates with and without nebular emissions. The star formation rate (SFR) in this galaxy ranges from 8 to 60Mo/yr, the stellar mass is in the order of (2.5-10) x 10^9 Mo and the size r=0.35+/-0.15 kpc, and it is consistent with expectations and previous estimates in this range of redshift. The brightness of this galaxy (F160W=26.2 AB) makes it one of the brightest z=8 object to date, and could be observed by current NIR-spectrograph in a reasonable amount of time.

Twenty years ago, no one convincingly knew the age or the size of the
Universe to within a factor of two. Ten years ago, everyone agreed on
those same two numbers to within 10%. Today, we arguably have brought
the errors down by another factor of two. But that has led to anxiety
rather than euphoria, renewed interest rather than complacency. The
problem is that there are now two independent, competing methods
giving answers of comparable precision and accuracy:
one is a model-based method using the cosmic microwave background
(the CMB), the other is a geometric, parallax-based method using local
measures of distances and expansion velocities. To within about
two-sigma the methods agree.  To within about two-sigma the methods
disagree. And basic physics (a fourth neutrino species, perhaps) hangs
in the balance.

I will discuss how this "tension" arose and how it will soon be
relieved.  A tie-breaker has been identified and developed, and it is
now being worked on from the ground and from space.

European Research Council (ERC) grants support individual researchers of any nationality and age who wish to pursue their frontier research. The ERC encourages in particular proposals that cross disciplinary boundaries, pioneering ideas that address new and emerging fields and applications that introduce unconventional, innovative approaches. ERC grants are awarded through open competition to projects headed by starting and established researchers - the sole criterion for selection is scientific excellence.

ERC grants are part of the European Horizon 2020 programme for research and innovation. Last December the ERC published the new work programme containing the first ERC calls under Horizon 2020. To gain an overall view of the rules and possibilities, we cordially invite you for an ERC information session.

Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions. Currently known black holes are fed by material stripped from a low-mass star or by the wind of a massive companion. Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly spinning Be-type stars. However, among the ~80 Be X-ray binaries known in the Galaxy (~150 including the Magellanic Clouds), only pulsating neutron stars have been found as companions, which is known as the missing Be/black-hole X-ray binary problem. In this talk I present the first dynamical evidence for a 3.8-6.9 Msun black hole orbiting the Be star and gamma-ray candidate MWC 656 (=AGL J2241+4454). This discovery has been allowed by the detection of a HeII emission line from an accretion disc encircling the black hole. We find the black hole is X-ray quiescent with Lx<1.6 × 10−7 times the Eddington luminosity. This implies that Be binaries with black-hole companions are difficult to detect by conventional X-ray surveys and may be more abundant than predicted by population synthesis models.

Gaia - the ESA cornerstone astrometric mission - was launched in December 2013, with the goal of censing the Milky Way population in a 6D space (positions and velocity) of 10^9 point-like obects, with errors
100-1000 times smaller than Hipparcos, with three color magnitudes and spectra as well. The scientific impact of its data will be large in many fields of astrophysics, from Galactic science, to Solar system objects, to stellar astrophysics, to galaxies and Quasars; from the distance ladder revision to fundamental physics. I will describe the mission concept, the scientific goals, and the present status of the mission, with special attention to the flux calibration of Gaia data.

Two main families of models explain that, at least in appearance, something like 90% of the mass of the Universe is still undetected. One (supported by an overwhelmingly large fraction of the community) is the dark matter model, in which the missing mass is postulated to be made of exotic non-baryonic particles. The other one, is modifying gravity (MOND, MOG, ...) in such a way that it compensates the apparent lack of mass. Both approaches are purely ad-hoc and so far not based in first principles of fundamental physics. Since I am not a specialist, in dark matter or modified gravities, the talk I am proposing is intended to be made purely from a philosophical/sociological/historical point of view. I expect the talk to be an open debate. The philosophical thesis I will defend is that the order in the discovery of some astronomical landmarks has led the community to favour dark matter model. In my opinion, this has caused darkmatter to receive a larger funding and become more successful at describing reality than alternative models. I will try to expose to the audience that, from a purely philosophical point of view, the dark matter model and the modified gravity models are equally speculative and equally (in)valid. I will make the point that dark matter has to be taken only as an extremely complex model which is useful for the description of reality and not as reality itself.

En esta ponencia se mostrarán los resultados fundamentales de dos de los trabajos de arqueoastronomía más recientes publicados por nuestro equipo en los desiertos de Arabia, uno sobre el País de Magan (actuales Oman y EAU) donde se analizarán las tumbas de la  Edad del Bronce (c. 3000 a.C.) y otro sobre el Reino Nabateo y su capital Petra, mostrando los resultados más singulares y llamativos.

The nearby spiral galaxy M81 contains a population of 3 kinds of stellar clusters - super star clusters, globular clusters and fuzzy clusters. Over the past few years, we have taken GTC longslit spectra of around 20 of these clusters, with the intention of obtaining their spectroscopic ages. These spectra have allowed us to understand the nature of the brightest globular cluster in this galaxy. In addition, we were able to address the problem of the origin of the fuzzy clusters. In the talk, I will summarize the results we have obtained so far.