Recent Talks

Pandas is an open source Python package that is widely used for data analysis. It is a powerful ally for data munging/wrangling and databases manipulation/visualisation, and a must-have tool for Data Scientists. In this seminar we will have a general overview on its functionality and we will run over some of the reasons of its large success in the Data Science community.

Gaia has provided distances and photometry, and thus colour-magnitude diagrams in the absolute plane, for stars over a large volume in the Milky Way, encompassing significant fractions of the thin and thick disk, and halo. This has allowed us, for the first time, to derive unprecedentedly detailed star formation histories from direct modelling of these colour-magnitude diagrams, using the same techniques that have been proven successful for external galaxies in the Local Group. Our first results for a volume of 2 Kpc radius from the Sun are extraordinarily promising. Applied to inner halo stars selected kinematically using Gaia proper motions, this technique has allowed us to date the merger of Gaia-Enceladus, to characterise the age profile of the accreted stars and of those present in the Milky Way at the time of the merger, and to detect a conspicuous burst of star formation in the thick disk occurred at the time of the merger (Gallart+2019). We have also obtained a representative SFH for the Galactic disk, which clearly shows the presence of up to four epochs of enhanced star formation well constrained in time, that can be associated with various pericentric passages of the Sgr dwarf galaxy (Ruiz-Lara+2020). Additionally, we are obtaining results of unprecedented clarity regarding the vertical distribution of ages and metallicities in the Milky Way disk. I will discuss these results as well as future prospects to reach a larger Milky Way volume, and to combine chemodynamical information from spectroscopic surveys with this new approach to study the Milky Way evolutionary history. 

In this talk I will discuss how the stellar, globular cluster (GC), and gas components of galaxies allow us to trace the assembly of galaxies and their dark matter (DM) haloes, and how they constrain the complex physics of galaxy formation. I will use examples from three studies: in the first one, I will describe how the study of the phase-space distribution of the MW GC system using Gaia in the context of the E-MOSAICS simulations provides a detailed quantitative picture of the formation of the Galaxy. In the second example, I will show how the unusual GC populations in galaxies like the infamous NGC1052-DF2 and DF4 can be used to rewind the clock and obtain a snapshot of their galactic progenitors at cosmic noon. A simple model of star cluster formation points to an extremely dense birth environment and strong structural evolution, providing clues of the effect of clustered star formation on galaxy evolution. In the last part I will describe a follow-up study of the impact of clustered star formation on galaxy structure that provides clues on the origin of ultra-diffuse galaxies (UDGs), which are difficult to explain in the current paradigm of galaxy formation. I will show how anchoring an analytical model on galaxy scaling relations and numerical simulations predicts the emergence of UDGs that lack DM driven by clustered feedback from young GCs.

En la presente charla hablaremos de la sobre la actualización que se está llevando a cabo en el software de control del Instrumento Gris de Gregor y como se ha intentado poner en marcha un sistema de integración continua. Además, se comentará la idea de montar un banco polar basado en un sistema de integración continua.

Durante el presente seminario hablaremos sobre el estado actual del banco óptico GTCAO. Se hará énfasis en las tareas mecánicas en curso referentes a las instalaciones auxiliares para la integración y comisionado del banco, planteando problemáticas generales de las tareas y soluciones adoptadas.

Enlace Youtube: https://youtu.be/4WTGKMGwd7o

In the last decade, Python went from being a moderated-used programming language in the astronomical community to the de-facto standard in Astronomy. Its recent growth has been spectacular, thanks to the coordination and work of the community to create astropy, the core astronomy library, as well as other base libraries like numpy and matplotlib. However, the current scientific/astronomical ecosystem for Python is huge and sparse, introducing many types of objects and methods, often confusing at the beginning.

In this SMACK talk I will describe the current status of the Python ecosystem for astronomy and introduce the most import elements of the core libraries, numpy and astropy, showing with practical examples how they provide new impressive capabilities to deal with data, catalogs, coordinates and much more, making life easier for astrophysicists.

The detections of gravitational waves are opening a new window to the Universe. The nature of black holes and neutron stars may now be unveiled, but gravitational radiation may also lead to exciting discoveries of new exotic compact objects, oblivious to electromagnetic waves. In particular, Advanced LIGO-Virgo recently reported a short gravitational-wave signal (GW190521) interpreted as a quasi-circular merger of black holes, one at least populating the pair-instability supernova gap. We found that GW190521 is also consistent with numerically simulated signals from head-on collisions of two (equal mass and spin) horizonless vector boson stars (aka Proca stars). This provides the first demonstration of close degeneracy between these two theoretical models, for a real gravitational-wave event. 

A la hora de planificar un proyecto la gestión de las dependencias técnicas entre tareas ya supone un desafío.  Añadamos a la coctelera las dependencias circunstanciales y, por qué no, sumerjamos el experimento en una organización matricial donde todos los miembros del equipo trabajan en varios proyectos.

"Classical Wolf-Rayet (WR) stars" represent a class of hot, hydrogen-depleted stars wtih powerful stellar winds and are prominent progenitors of black holes. Next to their unparalleled radiative and mechanical energy feedback, they offer unique probes of massive-star evolution at the upper-mass end. To become a classical WR star, single stars require substantial mass-loss to strip their outer, hydrogen-rich layers, implying that only very massive stars could enter the WR phase. However, mass-transfer in binaries can further aid in the stripping of stars and form Wolf-Rayet stars, or more generally helium stars, at lower masses.  Due to the decrease of mass-loss with metallicity, it has been predicted that WR stars at low metallicity tend to form in binaries. However, this has so far not been supported by observations.

In my talk, I will give an overview on our current knowledge of the properties of Wolf-Rayet populations in the Galaxy and the Magellanic Clouds based on exhaustive spectral analyses. I will illustrate why binary formation does not necessarily dominate the evolution of WR stars at low metallicity, and highlight important discrepancies between theory and observations of WR stars. I will discuss the observed rarity of intermediate mass helium stars, and present recent reports of unique helium stars in the exotic binaries LB-1 and HR 6819.