Recent Talks

In the early Universe, massive stars played a key role in the early chemical evolution of galaxies and in injecting important amount of ionising radiation in their environments. The first question that will be addressed in this seminar is the following one: can we infer some properties of the first stellar generations in the Universe by studying the surface composition of very metal poor stars in the halo of our Galaxy? The talk will focus on both the regular halo stars and the so-called Carbon Enhanced Metal Poor (CEMP) stars. The second topic that will be addressed in this talk deals with a much more recent event, the birth of the Solar System. Here the question will be: what do the presence of short lived radioactive elements in the proto-solar nebula tell us about the stellar environment of the Sun 4.56 billion years ago? The talk will focus on the discussion of the origin of 26Al and 60Fe in the proto-solar nebula.

The active galactic nuclei is conformed by a number of classes. Optically they are defined using diagnostics based on optical emission lines. At X-rays they are classified by the power of the AGN continuum and the shape of the X-ray spectra. Therefore, optical and X-ray classes are independent classifications. However, optical and X-ray classes show many discrepancies not fully understood yet. Some AGN at X-rays do not show any AGN signature at optical wavelengths (called optical elusive). Classical obscured AGN are ’sometimes’ not obscured at X-rays.

We have studied the ‘synapses’ between them using artificial neural networks (Gonzalez-Martin+14). To do so, we used flux-calibrated X-ray spectra of a sample of 90 emission line nuclei (ELN) observed with XMM-Newton. It includes starbursts (SB), transition objects (T2), LINERs (L1.8 and L2), and Seyferts (S1, S1.8, and S2).

The ELN can be classified into six classes, based on the shape of their X-ray spectra. These classes are associated with most of the optical classes. The key parameters to explain them at X-rays are three. The first parameter is an AGN-like component, which is present in all of them (even non-AGN at optical wavelengths!). The second one is obscuration, which almost certainly drives the Type-1/Type-2 dichotomy, but may also explain why L1.8 are more similar to S1s while L2/T2 are more similar to S1.8s. The third component is star-forming activity happening at the host galaxy and contributing at X-rays. The AGN strength, relative to the host-galaxy component, determines the average X-ray spectrum for these classes as follows: S1 -> S1.8 -> L1.8/S2 -> L2/T2/ -> SB.

There is an increasing multiplicity of proposed methodologies to derive chemical abundances in HII regions from the measurement of the relative fluxes of their optical emission lines. Particularly there is a known discrepancy between the prediction of some widely used grids of photoionization models and the results of the direct analysis of the spectra from their integrated physical properties (i.e. density, temperature). In this seminar, I will introduce HII-CHI-mistry, a Chi square approximation to compare observations with results of a large grid of models calculated using CLOUDY and varying the oxygen abundance, the nitrogen-to-oxygen ratio and the ionization parameter, covereing all possible conditions observed so far in massive complexes of star-formation. Including N/O as an additional variable allows the correct interpretation of the [NII] 6584 emission lines, widely used to derive abundances both in the Local and the Early Universe in the infra-red part of the spectrum.

The use of this method leads to a derivation of both Z and N/O totally consistent with the results from the direct method when emission line ratios sensitive to the temperature are available (e.g. [OIII] 50007/4363). On the contrary, when these ratios are not available, what is the most common situation in metal-rich/distant objects, it is necessary to assume empirical constraints to the space of parameters covered by the model-grid to arrive to solutions in the whole range of metallicity. Among the applications of this methods it is a consistent study of the metallicity in a wide range of potential variations (e.g. gradients of Z in disc galaxies, mass-metallicity relation, etc ...)

There is increasing speculation that quasars are intimately linked to the evolution of their host galaxies. Not only are they triggered as galaxies build up mass through gas accretion, but they also have the potential to drive massive outflows that can directly affect galaxy evolution by heating the gas and expelling it from galaxy bulges. However, there remain considerable uncertainties about how, when and where quasars are triggered as galaxies evolve, and the true energetic significance for the quasar-induced outflows and their acceleration mechanism have yet to be established. In this talk I will present new Gemini, VLT, Spitzer and Herschel results on samples of luminous AGN in the local Universe which provide key information on the triggering mechanisms for quasars and physics of their outflows.

I will present an evolutionary model for the origin of Andromeda II, a dSph satellite of M31, involving a merger between two disky dwarf galaxies than explains the origin of prolate rotation recently detected in the kinematic data for And II. The simulation traces the evolution of two dwarfs, whose structural parameters differ only in their disk scale lengths, placed on a radial orbit towards each other with their angular momenta inclined by 90 deg. After 5 Gyr the merger remnant forms a stable triaxial galaxy with rotation only around the longest axis. This prolate rotation is naturally explained as due to the symmetry of the initial configuration which leads to the conservation of angular momentum components along the direction of the merger. The stars originating from the two dwarfs show significantly different surface density profiles while having very similar kinematics in agreement with the properties of separate stellar populations in And II. I will also discuss an alternative scenario for the formation of And II, via tidal stirring of a disky dwarf galaxy. While intrinsic rotation occurs naturally in this model as a remnant of the initial rotation of the disk, it is mostly around the shortest axis of the stellar component. The rotation around the longest axis is induced only occasionally and remains much smaller that the system's velocity dispersion. I conclude that although tidal origin of the velocity distribution in And II cannot be excluded, it is much more naturally explained within the scenario involving a past merger event. Thus, in principle, the presence of prolate rotation in dSph galaxies of the Local Group and beyond may be used as an indicator of major mergers in their history or even as a way to distinguish between the two scenarios of their formation.

The Extreme Universe Space Observatory (EUSO) Space Program on the International Space Station (ISS) is the first space-based mission worldwide in the field of Ultra High Energy Cosmic Rays (UHECR) and Extremely High Energy Cosmic Rays (EHECR) and will contribute to consolidate a new window in the astronomical observation at the highest energies never observed neither with ground-based nor space-based experiments. Currently the international groups working on ground-based UHECR experiments are organized in the Pierre Auger Collaboration (Argentina, South Hemisphere) and the
Telescope Array Collaboration (Utah, North Hemisphere). JEM-EUSO will pioneer from Space the observation from ISS (North & South Hemispheres) of the non thermal Universe and will provide a real breakthrough toward the understanding of the Extreme Universe at the highest energies never detected from Space. In this Severo Ochoa Seminar an overview of the JEM-EUSO Space Mission and the pathfinders currently being developed, EUSO-BALLOON of the French Space Agency (CNES) and MINI-EUSO (ISS) of the Russian Space Agency (Roscosmos) will be presented. Moreover the Spanish Contribution to this EUSO Program under a Coordinated Proposal of MINECO, that involves Instituto de Astrofísica de Canarias (IAC), Instituto Nacional de Técnica Aerospacial (INTA), Universidad Politécnica de Madrid (UPM), Univesidad de Leon (ULE) and Universidad de Alcalá (UAH) will be reviewed as well.

I will discuss recent development in low noise amplifiers for astrophysical applications.
I will describe the fundamental quantum limits of linear amplifiers and then I will show how a
promising new class of amplifiers - superconducting parametric amplifiers - might be able to  (apparently) violate the Heisenberg Uncertainty Principle.

En esta charla se presenta una puesta al día de los resultados más importantes de un estudio arqueoastronómico interdisciplinar realizado en varias decenas de yacimientos arqueológicos de las culturas ibérica y tartesia del primer milenio a.C. en el levante y sur peninsular. En el caso de los templos tartésicos, posiblemente muy influidos o construidos por colonos fenicios, muestran un patrón de orientación muy bien definido que podría estar relacionado con el ocaso más meridional de Venus y, posiblemente, con el culto a la diosa fenicia Astarté, asociada a dicho planeta según los historiadores de la antigüedad. Por otra parte, encontramos que una fracción importante de los santuarios ibéricos estudiados, todos ellos dedicados a una diosa femenina, muestran marcadores del orto u ocaso solar sobre elementos destacados del horizonte en los equinoccios o una fecha muy cercana a estos, posiblemente el punto medio temporal entre solsticios. Esta relación astronómica equinoccial, la más clara de todas las encontradas en el mundo ibérico, sugiere la existencia de ritos asociados a la estacionalidad, festividades agrarias de la fecundidad similares a otras bien conocidas del Mediterráneo antiguo. La cronología más temprana de los santuarios relacionados con los equinoccios indican que comenzaron a funcionar alrededor de mediados del siglo IV a.C., momento de cambios importantes en la ideología de la sociedad ibérica y de un incremento de la influencia cartaginesa en la zona.

The Magellanic Clouds are the closest star forming galaxies, and their star formation histories can be derived in great details from color-magnitude diagrams reaching the oldest main sequence turnoffs. In the last several years, we have been conducting a wide research program on the Magellanic Clouds, including both photometry and spectroscopy, and have analysed the star formation history across both the Large and the Small Magellanic Clouds. This has revealed the nature of the stellar population gradients of these galaxies, as well as signatures that can possibly be related to their interaction history, among them and with the Milky Way.

This paper discusses how cosmic gas accretion controls star formation, and summarizes the physical properties expected for the cosmic gas accreted by galaxies. The paper also collects observational evidence for gas accretion sustaining star formation. It reviews evidence inferred from neutral and ionized hydrogen, as well as from stars. A number of properties characterizing large samples of star-forming galaxies can be explained by metal-poor gas accretion, in particular, the relationship between stellar mass, metallicity, and star formation rate (the so-called fundamental metallicity relationship). They are put forward and analyzed. Theory predicts gas accretion to be particularly important at high redshift, so indications based on distant objects are reviewed, including the global star formation history of the universe, and the gas around galaxies as inferred from absorption features in the spectra of background sources.