Recent Talks

We present a detailed study of the spatially resolved thermodynamic and hydrostatic mass profiles of the five most massive clusters detected at z~1 via the Sunyaev-Zel'dovich effect. These objects represent an ideal laboratory to test our models in a mass regime where structure formation is driven mainly by gravity. We present a method to study these objects that optimally exploits information from XMM-Newton and Chandra observations. The combination of Chandra’s excellent spatial resolution and XMM-Newton’s photon collecting power allows us to spatially resolve the profiles from the core to the outskirts, for the first time in such objects.  Evolution properties are investigated by comparison with the REXCESS  local galaxy cluster sample. Finally, we discuss the current limitations of this method in the context of  joint analysis of future Chandra and XMM large programs and, more generally, of  multi-wavelength efforts to study high redshift objects.

I will discuss our present knowledge of the statistics of stellar multiplicity (the multiplicity fraction and the distribution of periods, mass ratios, and eccentricities), and the implications for stellar evolution, in particular for Type Ia Supernovae (SN Ia). I will describe how multi-epoch radial velocity measurements from large spectroscopic surveys can open a new observational window on stellar multiplicity, and present two case studies: white dwarfs in SDSS/SEGUE and the ESO SPY survey, and main sequence stars and red giants in SDSS/APOGEE. For the white dwarfs, we can measure their merger rate and evaluate their viability as Type Ia SN progenitors. For the main sequence stars and red giants, we can explore the interplay between stellar evolution and stellar multiplicity, evaluate the rate of stellar mergers, and uncover a strong dependence of the multiplicity fraction with metallicity.

The IAC Solar System group has been cooperating with NASA’s OSIRIS-REx mission since 2011 when I became member of its Science Team. In 2015 we came to an agreement to be members of the Image Processing Working Group (IPWG) to perform two main tasks: produce and analyze the Color-ratio Maps and participate in the in-flight calibration of the cameras (OCAMS). Actually 5 members of our group are participating in the science of the mission.

OSIRIS-REx was launched in 2016 and will visit the asteroid Bennu. It will completely characterize Bennu during 2018-2019, and took a sample of material from the surface that will bring to Earth for detailed study in 2023. Bennu is the primitive near-Earth asteroid more accessible and is also one of the Potentially Hazardous asteroids most likely to collide with Earth. It is well stablished that primitive class asteroids are the parents of carbonaceous chondrite meteorites, the meteorites with the most primitive known composition. Their primitive nature and their water and complex organics content make their study have a high cosmogonic and astrobiological interest

With the aim of supporting the science return of OSIRIS-REx and other two missions (JAXA’s Hayabusa II and ESA’s MarcoPolo-R), we started in 2010 our PRIMitive Asteroids Spectroscopic Survey (PRIMASS). As part of the PRIMASS project, we are obtaining visible and near infrared spectra of the members of the primitive collisional families and dynamical groups of the main asteroid belt. 

In this seminar I will present OSIRIS-REx mission and summarize the research activities of the IAC Solar System group, in particular those related with our participation in the OSIRIS-REx mission: (1) the preparation for the analysis of OCAMS images using Dawn images of Ceres; (2) the spectroscopic characterization of the inner main belt primitive asteroids families from which Bennu likely came from.

The discovery of relic galaxies in our nearby Universe allow us to explore the physical conditions that took place at the early stages of galaxy formation (z>2) with unprecedented detail. In this talk, we will describe how these objects have been found, what is the physical motivation to explore them and what are the most relevant results we have learnt so far. In particular, in this seminar, we will focus on our recent publication in the journal Nature, where we study the globular cluster population of the massive compact relic galaxy NGC1277 using the Hubble Space Telescope. The analysis of its globular cluster population has confirmed the extraordinary nature of this object. This galaxy underwent  an early collapse phase but failed to evolve and accrete smaller satellite galaxies. The study of the globular cluster of this system (which has no similar counterpart in the near Universe) gives unique insights into the formation and evolutionary processes of the most massive galaxies.

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
the
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)
9 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
are.

KIC 8462852, also known as the Boyajian's star, was observed by the Kepler mission during 4 years. During that time, this star underwent several events of strong brightness variations that are unlike that of any other known astronomical object. Since 2017, an intense ground-based observing campaign has been under way to closely survey this target for further brightness variations. The coverage of several minor such variations from both multicolor photometry and spectrophotometry showed that these events have a color-signature. This observation is compatible with the hypothesis by Neslu?an & Budaj of a pool of dusty planetesimals that may occasionally pass close to the star. Their  optically thin dust shroud might then generate the observed colors. However, while current observations support this scenario, they do not prove it. Alternative explanations for the star’s behavior will be revised, and in particular, variations in the temperature of the stellar surface will be evaluated for their compatibility with the observations. Furthermore, an update on the observing campaign of Boyajian’s star will be given, possibly with input from new data acquired in the first half of 2018.

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.

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.

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. 

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.