Latest talks

List of all the talks in the archive, sorted by date.

Tuesday March 20, 2018
Dr. Enrica Bellocchi
Centro de Astrobiología de Madrid


The kinematic characterization of different galaxy populations is a key
observational input to distinguish between different galaxy evolutionary
scenarios, since it helps to determine the number ratio of rotating disks
to mergers at different cosmic epochs. Local luminous and ultra-luminous
infrared galaxies [(U)LIRGs] offer a unique opportunity to study at high
linear resolution and S/N extreme star forming events and compare them
with those observed at high z.
We obtained Very Large Telescope (VLT) VIMOS optical integral field
spectroscopy (IFS) data of a sample of 38 local (z < 0.1) (U)LIRGs (50
individual objects). Our goal is to analyze in detail the kinematics of
H\alpha ionized gas applying kinematic criteria able to characterize the
evolutionary status of these systems. In particular, the unweighted and
weighted kinemetry-based methods are used to kinematically classify our
galaxies in disk and merger. We also simulate our systems at z=3 to
evaluate how a loss of angular resolution affects our results.
From the kinemetry-based analysis we are able classify our local (U)LIRGs
in three distinct kinematic groups according to their total kinematic
asymmetry values (Ktot) as derived when using the weighted (unweighted)
method: 1) 25 out of 50 galaxies are kinematically classified as disk; 2)
out of 50 galaxies are kinematically classified as merger; 3) 16 out of 50
galaxies lie in the transition region, in which disks and mergers coexist.
When we apply our criteria to the high-z simulated systems, a lower total
kinematic asymmetry frontier value is derived with respect to that found
locally. The loss of angular resolution smears out the kinematic features,
thus making objects to appear more kinematically regular than actually they

Wednesday March 14, 2018
Dr. Begoña Vila Costas


The James Webb Space Telescope is the largest, most complex telescope being launched to date. It includes segmented folded mirrors and a folded sunshield deploying on orbit and instruments with state of the art infrared detectors and different science capabilities operating below 45K (-228 C).
A rigorous test campaign including ambient and cryogenic tests to verify the health, performance and operations readiness in the conditions it will see on orbit is near its completion. We will talk about some of those tests and their challenges as all the observatory components get assembled, covering in particular the comprehensive program of thermal, optical, electrical and operational tests in the cryogenic chambers at Goddard Space Flight Center and Johnson Space Center. We will talk also about how the telescope achieves the pointing stability required for science operations by using the various components of its Fine Guidance System.

Thursday March 8, 2018
Dr. Hector Socas Navarro


This paper puts forward a possible new indicator for the presence of moderately advanced civilizations on transiting exoplanets. The idea is to examine the region of space around a planet where potential geostationary or geosynchronous satellites would orbit (herafter, the Clarke exobelt). Civilizations with a high density of devices and/or space junk in that region, but otherwise similar to ours in terms of space technology (our working definition of “moderately advanced”), may leave a noticeable imprint on the light curve of the parent star. The main contribution to such signature comes from the exobelt edge, where its opacity is maximum due to geometrical projection. Numerical simulations have been conducted for a variety of possible scenarios. In some cases, a Clarke exobelt with a fraction alface-on opacity of ∼10^{-4} would be easily observable with existing instrumentation. Simulations of Clarke exobelts and natural rings are used to quantify how they can be distinguished by their light curve.

To appear in ApJ.

Wednesday March 7, 2018
Dr. Olga Zamora, Juan José Sanabria y Francisco Javier Hernández


En esta charla hablaremos sobre el proceso de actualización
del telescopio IAC80 en los últimos años, con el objetivo de llevar a cabo
observaciones muy exigentes en cuanto a número de imágenes, precisión temporal y astrométrica.
Se presentará la nueva cámara de gran campo CAMELOT-2
y su interfaz inteligente de usuario, que permite una observación cuasi-robótica por medio de macros
automáticas. Por último, se presentará el diseño del nuevo sistema de control, base de una futura robotización.

Tuesday March 6, 2018
Dr. Giuseppina Battaglia


In a framework where galaxies form hierarchically, extended stellar haloes are predicted to be an ubiquitous feature around Milky Way-like galaxies and to consist mainly of the shredded stellar component of smaller galactic systems. The type of accreted stellar systems are expected to vary according to the specific accretion and merging history of a given galaxy, and so is the fraction of stars formed in situ versus accreted. Analysis of the chemical properties of Milky Way halo stars out to large Galactocentric radii can provide important insights into the properties of the environment in which the stars that contributed to the build-up of different regions of the Milky Way stellar halo formed. In this talk I will first give an overview of some of the main properties of the Milky Way stellar halo based on literature studies. I will then present results concerning the chemical properties of the outer regions of the Milky Way stellar halo, based on the elemental abundances of halo stars with large present-day Galactocentric distances, >15 kpc. The data-set we acquired consists of high resolution HET/HRS, Magellan/MIKE and VLT/UVES spectra for 28 red giant branch stars covering a wide metallicity range, -3.1 ≲ [Fe/H] ≲-0.6. We show that the ratio of α-elements over Fe as a function of [Fe/H] for our sample of outer halo stars is not dissimilar from the pattern shown by MW halo stars from solar neighborhood samples. On the other hand, significant differences appear at [Fe/H] ≳-1.5 when considering chemical abundance ratios such as [Ba/Fe], [Na/Fe], [Ni/Fe], [Eu/Fe], [Ba/Y]. Qualitatively, this type of chemical abundance trends are observed in massive dwarf galaxies, such as Sagittarius and the Large Magellanic Cloud. This appears to suggest a larger contribution in the outer halo of stars formed in an environment with high initial star formation rate and already polluted by asymptotic giant branch stars with respect to inner halo samples. 

Thursday February 22, 2018
Dr. Habib Khosroshahi
School of Astronomy, IPM - Tehran


Galaxy groups and clusters are believed to influence galaxy evolution. It has been shown that the groups with early formation epoch, also known as fossil groups, differ in halo and IGM properties, compared to the general population of galaxy groups. However, there is a controversy over the properties of the brightest group galaxies which may have been affected by the group's dynamical state. I will focus on two properties of the brightest group galaxies, the AGN activity and the stellar population. The groups with early formation epoch, or dynamically old, host under luminous AGNs in radio relative to those hosted by dynamically young groups. There is no evidence that such a distinction exists in the stellar population of these galaxies, leaving the debate open whether this is an observational limitation. 

Thursday February 8, 2018
Dr. Alessandro Lupi
Institut d'astrophysique de Paris


Molecular hydrogen (H2) is a fundamental component of galaxies, being the most abundant element in molecular clouds, where stars form, and an important source of radiative cooling at low temperature. With the advent of the ALMA telescope, a large amount of data about the distribution of H2 in galaxies has become available. However, the large majority of numerical simulations on galactic and cosmological scales still lacks the ability to directly follow the formation and dissociation of H2, and must rely on pre-calibrated sub-grid models to compare the results with observations. I will present a new model to self-consistently track the evolution of H2, including gas and dust shielding, H2 self-shielding, star formation (SF), supernova feedback, and extragalactic and local stellar radiation. I will discuss the results of a suite of hydrodynamic simulations of an isolated gas-rich galaxy at z=3, showing that the model can naturally reproduce the observed correlation between SF and H2 surface densities, without assuming any a priori dependence of SF on the H2 abundance. I will also present a study of the kinematics and dynamics of molecular gas in high-redshift quasars (z=6), where we investigate whether a central accreting black hole (BH) can significantly affect the H2 distribution in the host galaxy and generate molecular outflows.

Thursday February 1, 2018
Dr. Savita Mathur


More than 40 years ago, Skumanich (1972) showed how rotation and magnetic activity decreased with the age of a solar-like star. While this result was based on the study of young cluster stars, later observations  of other clusters, still younger than the Sun, agreed with this “gyrochronology” relationship.

With the high-quality photometric data collected by the Kepler mission, we have the opportunity to test and study the evolution of stellar dynamics to older field stars. While for clusters, the determination of stellar ages is eased by the fact that the stars were born from the same molecular cloud, it gets trickier and less precise for field stars. This is where asteroseismology plays an important role by providing more precise ages than any other classical methods.

In this talk I will mostly focus on asteroseismic targets from solar-like stars to red giants where we could measure surface rotation, core rotation, and magnetic activity. I will show how the photometric data of Kepler is providing key information in the understanding of angular momentum transport in stars and of magnetic activity at different evolutionary stages of a star like the Sun.

Tuesday January 23, 2018
Dr. Kris Youakim
Leibniz-Institut für Astrophysik Potsdam (AIP)


The most metal-poor stars in the Galaxy are relics from the first generations of star formation, and their properties can reveal key information about the formation and evolution of the Milky Way. However, only a small number of these extremely rare stars are currently known, due to the difficulty in finding them amongst the overwhelmingly more abundant stars of higher metallicity. In this talk, I will present the Pristine survey, a narrow-band photometric survey in the wavelength region around the Ca H&K absorption lines designed to efficiently search for extremely metal-poor (EMP) stars. In the first three years of the survey, we have covered ~2,500 square degrees of sky in the Northern hemisphere using the CFHT on Mauna Kea in Hawaii, as well as a sizeable spectroscopic follow-up sample using mostly the INT and WHT in La Palma. With this data, we have demonstrated success rates of 70% for finding stars with [Fe/H] < -2.5, and 22% for stars with [Fe/H] < -3.0. This represents a significant improvement upon previous searches for EMP stars, which have reported success rates of 3-4%. With this efficiency, the Pristine survey is poised to make a significant contribution to constraining the metal-poor tail of the metallicity distribution function, as well as increasing the number of known ultra metal-poor (UMP) stars in the literature. In addition, I will discuss how the Pristine survey is being used to characterise the faint dwarf galaxy population, and analyse substructure in the Galactic Halo.

Tuesday January 16, 2018
Dr. Carlos del Burgo


We employ a Bayesian method to infer stellar parameters from the PARSEC  v1.2S library of stellar evolution models and test the accuracy of these theoretical predictions. Detached eclipsing binaries are ideal for testing. We employ a compilation of 165 detached eclipsing binary systems of our galaxy and the Magellanic clouds with reliable metallicities and measurements for the mass and radius to 2 per cent precision for most of them. We complement the analysis with 107 stars that are closer than 300 pc, for which we adopted solar metallicity. The applied Bayesian analysis relies on a prior for the initial mass function and flat priors for age and metallicity, and it takes on input the effective temperature, radius, and metallicity, and their uncertainties, returning theoretical predictions for other stellar parameters of the binaries. Our research is mainly based on the comparison of dynamical masses with the theoretical predictions for the selected binary systems. We determine the precision of the models. Also, we derive distances for the binaries, which are compared with trigonometric parallaxes whenever possible. We discuss the effects of evolution and the challenges associated with the determination of theoretical stellar ages.

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