Recent Talks

Galaxy surveys of the next decade will observe hundreds of millions of galaxies over unprecedented cosmic volumes. They will produce detailed 3D maps of the Universe that we can use to precisely measure the growth and expansion histories of the Universe. They will also observe photometry and spectroscopy of each galaxy that encode its physical properties. In my talk, I will present how we will extract this cosmological information from the major galaxy surveys that I am leading: the Dark Energy Spectroscopic Instrument (DESI) and the Prime Focus Spectrograph (PFS). Furthermore, I will demonstrate how my work, ranging from survey design to the cutting-edge machine learning methods I have pioneered, will maximize the scientific impact of these surveys. In particular, I will show how I will test the standard "Lambda-CDM" cosmological model in new regimes and with unmatched precision to probe the nature of dark energy. I will also show how I will extract detailed galaxy properties, such as star formation or chemical enrichment histories, of millions of galaxies across 12 billion years of cosmic history to constrain the physical processes that drive galaxy evolution.

Massive stars are chemical factories producing key elements, they are progenitors of supernovae, neutron stars and black holes, and they play a crucial role in the formation and evolution of galaxies. Given their prevalence in binary systems, at the end of their lives they may produce double-compact objects, which are potential gravitational-wave sources. During their life cycles, interactions with their companion stars can drastically alter the evolution of both stars. Yet, the complex interaction physics as well as the outcome of the interactions remain poorly understood. One way of constraining those is by observing post-interaction binaries.

A century-old question in the context of massive stars addresses the Be phenomenon, which occurs in ~20% of the early-type stars. Observationally, classical Be stars are defined as B-type stars with Balmer line emission, indicative of a circumstellar disk, which strongly correlates with rapid rotation of the star. While the processes that lead to such high rotation rates are still widely debated, classical Be stars were proposed to be mass gainers in previous binary interactions. If true, that would make them post-interaction binaries with stripped-star or compact-object companions.

In my talk, I will discuss the different channels proposed for the formation of classical Be stars, with a particular focus on the binary channel. I will present observational evidence suggesting that the binary channel is indeed predominant in the formation of massive Be stars, and will show that the few known Be binaries are exotic systems with stripped or compact companions. I will furthermore discuss what those systems can teach us about binary interaction physics and thus about massive-star evolution in general.

Diseño, construcción y primera luz del EMO-1, un observatorio casero con estación meteorológica integrada, monitoreo permanente del cielo y colaboración científica.

Youtube:
https://youtube.com/live/0PFICuLjOAE?feature=share

Molecules play a crucial role in all branches of astrophysics, particularly in the analysis of planetary and stellar spectra, as well as contributing to the all important envelope opacities needed for modelling the evolution of cool stars.  Until 2010, line positions and strengths for all astrophysically important molecules were sparse, and the ExoMol project was setup by Jonathan Tennyson and Sergey Yurchencko in 2011 to use state-of-the-art quantum mechanics to calculate the billions of line strengths and positions needed for all molecules of interest.  As well as describing the ExoMol project, I plan to discuss my own contribution, which involves the C3 molecule and its isotopologues.

En esta charla se va a presentar los telescopios ATLAS y su integración en la red ATLAS dirigida por la Universidad de Hawaii. Vamos a hablar del estado actual del proyecto, tecnología que se utiliza en los telescopios y el stack software que lleva asociado.

Activity of cool dwarf stars can reveal itself in the form of high-energy radiation (eg, enhanced X-ray coronal emission, flares) and particles (eg, winds, coronal mass ejections). Together, these phenomena shape the space weather around (exo)planets. Because most of the known exoplanets have significantly closer orbital distances than solar system planets, they are often embedded in much harsher particle and radiation environments, leading to stronger interactions between the exoplanet and its surrounding environment. In this talk I will present an overview of how stellar activity and outflows can induce and shape atmospheric escape in exoplanets. I will focus mostly on close-in gas giant planets, whose escaping atmospheres are somewhat easier to observe. I will then discuss how the observability of atmospheric escape, through spectroscopic transits, evolve on billions of years timescales.

The coupling between the baryonic cycle of galaxies and dark matter halo assembly is central to our understanding of galaxies, and yet, it remains a challenge for theoretical models and elusive to observations. In this talk, I report observational evidence demonstrating that different baryonic properties of nearby galaxies are controlled by their host halos. We map galaxy ages, metallicities and star formation histories across the stellar-to-halo mass relation for SDSS central galaxies using absorption optical spectra. In addition to stellar populations, we also investigate the stellar angular momentum, star formation rates and galaxy morphology across the stellar-to-total dynamical mass relation for CALIFA galaxies. We find that the scatter of both relations correlates with these galaxy properties, which are determined by the combined role of stellar and halo/total mass. Galaxies become older, more metal-rich and less rotationally supported, form the bulk of their stars earlier on and faster, have lower star formation rates and earlier-type morphologies as their stellar mass increases (at fixed halo/total mass). Furthermore, we also observe that the scatter of the star-forming main sequence is driven by galaxies that have experienced different evolutionary histories. We interpret our results as being driven by halo evolution, with galaxies/halos at different evolutionary stages modulating the variety of galaxy properties observed at fixed stellar mass. Our findings call for a revision of the sub-grid physics implementation in cosmological numerical simulations, in particular during the early stages of galaxy formation, and warn observational studies to account for the profound effect that halo formation time may have on measured galaxy properties.

Zoom Link: https://rediris.zoom.us/j/96210828127?pwd=Z25JdFg1bnpRTVBSQUdpTVlwUDgyQT09