Recent Talks

This talk will give an overview of the resources for scientific computing at the IAC. The network, los burros, and LaPalma will be described, together with the basics for using them and practical examples. 

Speakers: Ana Esteban, Carlos Allende, Isaac Alonso and Juan Carlos Trelles (IAC)

HORUS (High ResolUtion Spectrograph) es un espectrógrafo de alta resolución, instrumento visitante en GTC y disponible para la comunicad científica desde prinicipios de 2019. Instalado en la plataforma Nasmyth B, detrás de OSIRIS, comparte foco con él. En esta charla se describe su software de control, resaltando la implementación realizada para ser un instrumento visitante de GTC y cómo se ha resuelto el problema del apuntado de un objeto.

IAC leads the extragalactic ESO Public Survey SHARKS (Southern H-ATLAS Regions Ks band Survey; PI: H. Dannerbauer). We survey with the ESO 4m telescope VISTA and the near-infrared camera VIRCAM more than 300 square degrees at 2micron with the near-infrared filter K_s, reaching a depth of K_s~22.7 (AB) with 1200 hours of observations. The covered fields have been previously observed with the infrared space telescope Herschel. Optical coverage already exists from the Dark Energy  Survey and the Hyper Suprime-Cam Subaru Strategic Program. In the future, these fields will be observed with the SKA-precursor ASKAP, EUCLID, LSST and eROSITA. Thus due to its exquisite multi-wavelength coverage, this dataset has a huge legacy value. The principal aims of the survey are: i) to search for counterparts of infrared and radio-selected sources, ii) to study the evolution of the most massive structures in the Universe and iii) to produce a sample of a thousand strong lenses for cosmography studies. Nonetheless, given its sensitivity and wide-area coverage in the near-infrared, it represents an excellent data-set for a wide range of astrophysical studies beyond their initial objectives, including the study of ultracool dwarfs in the Milky Way and high-redshift quasars. Currently, we are preparing the first public data release (DR1) of SHARKS at ESO. In this talk I will introduce the science that can be done with SHARKS. Finally, I will present the current status of the project, including a first look up at the DR1, and try to encourage the community to exploit this outstanding dataset.

Following up on our previous "Git version control system basics" seminar (https://bit.ly/35CCX7k), the focus of this talk will be to learn the features of Git that will allow us to collaborate with other colleagues. For this, the main concepts needed are branch merging (including merges with conflicts), remote repositories and hosted repositories (GitHub, GitLab, Bitbucket, etc.). 

Thanks to the distributed structure of Git, collaboration with colleagues can become very efficient (allowing for many different workflows) and it avoids the single point of failure of centralized version control systems, but its complexity also goes up. Properly understanding the concept of remote repositories makes collaboration with Git straightforward.

Other Git features and tools that are not essential, but that will make Git usage much more effective and powerful (like stash, rebase, pull requests, etc.) will be left for a planned "Advanced Git" follow-up talk.

Massive stars are often found to be in pairs. This configuration is both a blessing and a curse. From it, we can estimate their exact properties such as their masses but the interactions that result during their life considerably affect the way that the stars evolve.

Here, we provide an overview of progresses made through a number of medium and large surveys. These results provide new insights on the observed and intrinsic multiplicity properties of massive stars through a large range of masses and at different metallicities. Furthermore, to understand how the stars evolve when they are in pair and what are the effects of these interactions on the stellar properties, we undertook a large study of more than 60 massive binaries at Galactic and LMC metallicities using spectral disentangling, atmosphere modelling and light curve fitting to determine their stellar parameters, and surface abundances. This unique dataset is the largest sample of binaries composed of at least one O-type star to be studied in such a homogeneous way. It allows us to give strong observational constraints to test theoretical binary evolutionary tracks, to probe rotational and tidal mixings and mass transfer episodes.

Git is probably the most widely used Version Control System (software tools that help record changes to files (computer code, text files, etc.) by keeping track of modifications done through time). It can be used for any type of text files, though it is specially useful for programming code and it makes managing your projects, files, and changes made to them much easier and more intuitive.

But it is a big and complex system and people new to it can have a hard time mastering it. In this talk I will introduce the git version control system to people that have never used it before, so I will go over its basic concepts and functionalities from the ground-up. I will cover the most common commands, needed to use Git for your own individual projects. Once you properly understand how to use it on your own, it is much easier to understand how to collaborate with others (for example using GitHub), which will be covered in a follow-up talk: "Intermediate Git".

Galaxy clusters are the most massive gravitationally bound structures in the Universe. They are the sites where exceptional morphological transformations of galaxies occur, driven by their interactions within the complex cosmic web. Clusters are thus excellent laboratories to study galaxy evolution in extreme regimes. I will present the results of a large campaign based on IRAM facilities (30m and NOEMA) and targeting in mm different samples of galaxies in and around clusters. The final goal of the project is to evaluate the role of dense mega-parsec scale environments in processing cold gas of galaxies. The following samples of galaxies will be discussed. i) The largest sample of distant ~30 brightest cluster galaxies observed in CO, over a broad range of redshift (z~0.2-2.6). They are drawn from CLASH, COSMOS, SpARCS, and DES deep fields. ii) The largest sample of distant, intermediate redshift z~0.2-0.5, cluster LIRGs (luminous infrared galaxies), which have been observed in CO with the NOEMA interferometer and are drawn from the Herschel Lensing Survey (HLS) and the Local Cluster Substructure Survey (LoCuSS).  iii) I will also present ongoing results of a large campaign with the aim to evaluate the pre-processing of atomic (HI) and molecular (CO) gas of galaxies before they fall into the cluster core. The sample comprises 245 galaxies in cosmological filaments, up to 7 virial radii around Virgo, the benchmark cluster in the local Universe. The outlined studies reveal a complex scenario, where large-scale structures have a different impact in regulating the star formation fueling and mass assembly of the considered galaxies, depending on their morphological type, location with respect to the cluster core, and redshift.

https://rediris.zoom.us/j/83038801735

Stellar magnetic activity generates astrophysical noise on the collected data in the quest for what might be called Earth 2.0. This noise poses obstacles and difficulties in the detection and accurately determining small-sized exoplanets properties. Characterising the relation between stellar photometric variability and radial velocity jitter can help us to define optimal observational strategies, and also to better model and mitigate the activity noise. Moreover, stellar activity will remain as one of the biggest challenges in detecting and assessing the exoplanetary atmosphere’s signal, even in the era of upcoming missions. I will present the current view of the intricate relationship between exoplanets and activity, discuss some of the latest developments, and show some of our first results.

An original method for measuring the atmospheric turbulence is described, capable of even measuring the tip-tilt, which normally requires a dedicated natural star and nowadays defines the practical limit of the adaptive optics technique. The method is based in the illumination of a wide area of the Sodium Layer, and to use their inhomogeneities as a reference. Sevaral analysis and simulation results will be presented.

Zoom link:
https://rediris.zoom.us/j/87053930312

Enlace youtube: https://youtu.be/c1TCdt_-S_o

Reconstructing the past of the Milky Way depends on the study of its metal-poor stars, which either have been formed in the Galaxy itself in the first billion years, or have been accreted through mergers of satellite galaxies over time. These stars are usually found in what is known as the Milky Way halo, a light — in terms of total mass —  stellar component which is usually made of stars whose kinematics significantly deviates from that of the Galactic disc.
In this talk, I will discuss how it has been possible to use the astrometric and spectroscopic data delivered by Gaia and complementary surveys  to shed light on the past of our Galaxy, through the study of its halo. Besides the discovery of the possible last significant merger experienced by the Milky Way, the use of 6D phase space information and chemical abundances allowed to reconstruct the impact this merger had on the early Milky Way disc, and the time it occurred, as well as to discover that some of the most metal-poor stars in the Galaxy possibly formed in a disc.  This last finding would imply that the dissipative collapse that led to the formation of the old Galactic disc must have been extremely fast.