Recent Talks

An astrophysical black hole is completely described with just two parameters: its mass and its dimensionless spin. A few dozen black holes have mass estimates, but until recently none had a reliable spin estimate. The first spins have now been measured for black holes in X-ray binaries. The talk will describe the method used to make these measurements and will discuss implications of the results obtained so far.

Milky Way and most spiral galaxies present some features in the outer part of its disk such as S-warping or U-warping, flaring, lopsidedness, truncation/non-truncation and others, both for the stellar and the gas component. In the present talk, I will review some of the galactic dynamics hypotheses which try to explain these features: either in terms of gravitational interaction, magnetic fields, accretion of intergalactic matter or others. The gravitational interaction may be among the different components of the galaxy or between the spiral galaxy and another companion galaxy. The accretion of intergalactic matter may be either into the halo, with a later gravitational interaction between the misaligned halo and the disc, or directly onto the disc. The phenomena of the outer disc in spiral galaxies might be produced by more than a mechanism. Nonetheless, the hypothesis of accretion of intergalactic matter onto the disc presents several advantages over its competitors, since it explains most of the relevant observed features, whereas other hypotheses only explain them partially.

The present work shows the Spectral Energy Distributions (SEDs) in the near-infrared using the IRTF stellar library obtained using the models based on the Single Stellar population Models (SSP) from Vazdekis et al. (1996 - 2010) which work in the optical, and use the CaT and MILES stellar libraries. In this near-infrared research, the isochrones of Marigo et al. (2008) were chosen and which have a range of metallicity [Fe/H] between -2.27 and 0.019, and ages up to 15.85 Gy. Also, they provide the corresponding ?uxes in the IR bands I to M (0.7 to 5.0 microns). The IRTF stellar library contains spectra of 292 stars (F, G, K and M stars) at a resolution of 2000, between 0.8 to 5.2 microns. The features of the SED (spectrum obtained by the integration of the spectra of the stars, at constant metallicity and age) are analysed by comparing to those found on Ivanov et al. (2004) for the IR range. In addition, t he comparison of the models with galaxy observations of early type galaxies by Marmol-Queralto et al. (2009) are presented.

The MAGIC telescopes discovered very high energy (VHE, E>100 GeV) gamma-ray emission coming from the distant Flat Spectrum Radio Quasar (FSRQ) PKS 1222+21 (4C +21.35, z=0.432). It is the second most distant VHE gamma-ray source, with well measured redshift, detected until now. The detection coincides with high energy MeV/GeV gamma-ray activity measured by the Large Area Telescope (LAT) on board the Fermi satellite. The VHE and MeV/GeV spectra, corrected for the absorption by the extragalactic background light, can be described by a single power law with photon index 2.72 ± 0.34 between 3 GeV and 400 GeV, consistent with gamma-ray emission belonging to a single component in the jet. The absence of a spectral cutoff constrains the gamma-ray emission region to lie outside the Broad Line Region, which would otherwise absorb the VHE gamma-rays. On the other hand, the MAGIC measurement of a doubling time of about 9 minutes indicates an extremely compact emission region, in conflict with the "far dissipation" scenario. This result challenges jet emission models in FSRQs and indicates the importance of jet sub-structures.

The extragalactic background light (EBL) is of fundamental importance both for understanding the entire process of galaxy evolution and for gamma-ray astronomy, but the overall spectrum of the EBL between 0.1 and 1000 microns has never been determined directly from galaxy spectral energy distribution (SED) observations over a wide redshift range. Galaxy SED-type fractions from z=0.2-1 are estimated from a multi-wavelength sample from the AEGIS collaboration that allows a new determination of the evolving EBL. Then, the transparency of the Universe to very high energy (VHE) gamma-ray photons is derived. We find the maximum transparency of the Universe allowed by the standard framework. This result challenges current VHE observations of high redshift blazars. A solution to this problem is discussed utilizing VHE spectra of the highest redshift blazars assuming the existence of a plausible dark matter candidate known as axion-like particle.

I will present new mid-infrared imaging data for a sample of ~20 nearby Seyfert galaxies obtained with T-ReCS and MICHELLE on the Gemini Telescopes at subarcsecond resolution. Our aim is to compare the properties of Type-1 and Type-2 Seyfert tori using clumpy torus models and a Bayesian approach to fit the infrared nuclear spectral energy distributions (SEDs). These dusty tori have physical sizes smaller than 10 pc radius, as derived from our fits. Unification schemes of AGN account for a variety of observational differences in terms of viewing geometry. However, we find evidence that strong unification may not hold, and that the immediate dusty surroundings of Type-1 and Type-2 Seyfert nuclei are intrinsically different. The Type-2 tori studied here are broader, have more clumps, and these clumps have lower optical depths than those of Type-1 tori. The larger the covering factor of the torus, the smaller the probability of having direct view of the AGN, and vice-versa. In our sample, Seyfert 2 tori have larger covering factors and smaller escape probabilities than those of Seyfert 1. Thus, on the basis of the results presented here, the classification of a Seyfert galaxy as a Type-1 or Type-2 depends more on the intrinsic properties of the torus rather than on its mere inclination, in contradiction with the simplest unification model.

The Baryon Oscillation Spectroscopic Survey (BOSS) is a Stage III dark energy experiment on the Sloan Telescope. For the five years from 2009-2014, we are mapping 1.5 million galaxies at z<0.7. A simultaneous survey of 160,000 QSOs is mapping the hydrogen gas in absorption at redshifts 2 < z < 3. BOSS will provide the definitive measurement of the low redshift (z<0.7) BAO distance scale, and it will pioneer a powerful new method of measuring BAO at high redshift. BigBOSS is a proposed Stage IV dark energy experiment that will extend this map to 20 million galaxies over 14,000 deg² to z=1.7. I will describe this survey and its technical status.

Extended, diffuse radio emission (halos and relics) in galaxy clusters is a rare phenomenon. The origin of these radio sources and their connection with cluster mergers is still being debated. Here we present the results of the DARC program, aimed to the internal Dynamics Analysis of ”Radio” Clusters and mainly based on a long-term TNG-INT program (20 clusters at z=0.1-0.3). The study of kinematics of member galaxies show that DARC clusters are examples of very substructured systems and allow us to detect and weight the interveining subclusters, as well as to obtain infor- mation about their relative motions and the merger geometry. The multiwavelength observational picture (optical, radio and X-ray) of DARC clusters is well interpreted in a scenario of a recent, major cluster merger.

En mi conferencia haré una introducción a la Física Cuántica y a continuación pasaré a discutir diferentes casos en los que los fenómenos cuánticos juegan un papel determinante en el trabajo de diferentes máquinas médicas. De hecho, los ejemplos que explicaré recorrerán la historia de la medicina moderna, la del siglo XX, desde el punto de vista de la terapia como de la inspección. Para todo ello tendré que echar mano, por ejemplo, del principio de incertidumbre de Heisenberg, del efecto túnel de la corriente eléctrica y del espín, de la resonancia atómica. Todo ello para explicar, entre otros casos, cómo se “ve” el corazón, cómo se detectan los pensamientos, porque el feto de la madre roba el oxígeno a la sangre de su madre para poder vivir.

This question is important because a large fraction of planetary nebulae (about 80%) are bipolar or elliptical rather than spherically symmetric. Modern theories invoke magnetic fields, among other causes, to explain the rich variety of aspherical components observed in PNe, as ejected matter is trapped along magnetic field lines. But, until recently, this idea was mostly a theoretical claim. Jordan et al. (2005) report the detection of kG magnetic fields in the central star of two non-spherical PNe, namely NGC1360 and LSS1362. We find that, contrary to that work, the magnetic field is null within errors for both stars. Then, a direct evidence of magnetic fields on the central stars of PNe is still missing — either the magnetic field is much weaker (< 600 G) than previously reported, or more complex (thus leading to cancellations), or both. The role of magnetic fields shaping PNe is still an open question.