Recent Talks

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.

The discovery of earth-like planets is nowadays the main goal of the entire exoplanets field. Despite the recent success of transiting programs, the measurement of radial velocities (RV) is still the most powerful method to find them. M-Dwarfs, given their low masses, and close-in habitable zone have become the perfect targets for the current generation of spectrographs. In this talk I will present our own M-Dwarfs RV program here at the IAC, explaining our methods, goals, difficulties and preliminary results.

DESI is a massively multiplexed fiber-fed spectrograph that will make the next
major advance in dark energy in the timeframe 2018-2022. On the Mayall
telescope, DESI will obtain spectra and redshifts for tens of millions of
galaxies and cuasars with 5,000 fiber postioner robots, constructing a
3-dimensional map spanning the nearby universe to 10 billion light years. DESI
is supported by the US Department of Energy Office of Science to perform this
Stage IV dark energy measurement using baryon acoustic oscillations and other
techniques that rely on spectroscopic measurements. Spain has a major role in
DESI with the construction of the Focal Plate and the development of the fiber
positioners. I will give an overview of the DESI science, instrument, and Spain
participation in the project.

The robotic 2m Liverpool Telescope, based on La Palma, is owned and
operated by Liverpool John Moores University. It has a diverse
instrument suite and a strong track record in time domain science,
with highlights including early time photometry and spectra of
supernovae, measurements of the polarization of gamma-ray burst
afterglows, and high cadence light curves of transiting extrasolar
planets. In the next decade the time domain will become an
increasingly prominent part of the astronomical agenda with the
arrival of new facilities such as LSST, SKA, CTA, Gaia and the next
generation of exoplanet finders. Additionally, detections of
astrophysical gravitational wave and neutrino sources opening new
windows on the transient universe. To capitalise on this exciting new
era we intend to build Liverpool Telescope 2: a new robotic facility
on La Palma dedicated to time domain science. The next generation of
survey facilities will discover large numbers of variable and
transient objects, but there will be a pressing need for follow-up
observations for scientific exploitation, in particular spectroscopic
follow-up. Liverpool Telescope 2 will have a 4 metre aperture,
enabling optical/infrared spectroscopy of faint objects. Robotic
telescopes are capable of rapid reaction to unpredictable phenomena,
and for fast-fading transients like gamma-ray burst afterglows, this
rapid reaction enables observations which would be impossible on less
agile telescopes of much larger aperture. We intend Liverpool
Telescope 2 to have a world-leading response time, with the aim that
we will be taking data with a few tens of seconds of receipt of a
trigger from a ground- or space-based transient detection facility. In
this talk I will discuss the role for Liverpool Telescope 2 in the
2020+ astronomical landscape, the key science topics we hope to
address, and the results of our preliminary optical design studies.

Galaxy clusters are the perfect places to study both the always controversial nature vs nurture problem and the still not well understood evolution that galaxies follow. By studying the properties of the galaxies at different locations of the cluster we can assess the first problem, while studying the same properties over cosmic time, helps constraining the different proposed evolutionary theories. In this work we have focused in an intermediately-redshift rich cluster, RX J0152.7-1357 (z=0.83), by fully characterizing its stellar population properties with new state-of-the-art tools . By this means, we have derived for the first time in such a high-z cluster the ages, metallicities, abundance patterns and Star Formation Histories of the cluster ETGs on an individual galaxy-basis . The relations that these properties follow with galaxy velocity dispersion allow us to discuss a passive evolution scenario with respect to a cluster at z~0. Our results favor a downsizing picture where the relation between the position within the cluster, the velocity dispersion and the type of star formation history of the galaxies allow us to better understand the cluster evolution. We find that the most massive galaxies evolve passively while the lower-mass ones, generally located at the outskirts of the cluster, experience a more extended star formation history related to their later incorporation in the cluster.

The structure, kinematics and stellar population of the Galactic bulge is very complex. Only three years ago the bulge was discovered to be X-shaped, a structure believed to originate from the dynamical instabilities of a disk, through the formation and posterior heating of a bar. The study of its kinematics reveals a cylindrical rotation, typical of a bar, suggesting the absence of a spheroidal component. Nevertheless, the bulge stellar population is old, has a radial metallicity gradient, and element ratio indicative of a short formation timescale. All these elements conflict with a simplistic view of the bulge as a heated bar, formed via "secular" evolution of a disk. I will review our knowledge of the bulge properties as traced by the 3D structure, kinematics, and chemical composition of its red clump stars.