Recent Talks

At present, our understanding of the formation history of the MW is limited due to the complexity of observing the imprints of accretion events and of reproducing them in numerical simulations. Moreover, though being the only galaxy, in which the Galactic potential can be probed in detail, the distribution of mass in the MW, and hence of the dark matter, is poorly constraint, especially at large distances. In addition, the MW is not isolated, and it has recently been suggested that the infall of the LMC can induce a perturbation in the stellar and dark matter distribution of the MW. As a consequence, the details of the formation history of our Galaxy are still unknown, such as the number of accretion events, the mass of the accreted galaxies, and the epoch of these events. Yet, this information is crucial to understand our environment and to constrain the theoretical models and simulations that try to reproduce it. In this talk I will present recent works that have been conducted to better characterized our Galaxy and its history thanks to new large scale surveys that provide detailed dynamical and chemical information. I will also present the major improvement that will bring the new generation of large, multi-aspect surveys, to study both our Galactic history, as well as the fundamental nature of the dark matter.

Primitive asteroids are small bodies that have evolved relatively little since their formation. Their study is essential to understand the chemical composition of the early solar system and its evolution over the past 4.57 billion years. The understanding of the evolutionary processes of primitive asteroids is all the more important as these objects could have brought water and organic matter into the inner solar system.

In the 2010s, two space missions, OSIRIS-Rex (NASA) and Hayabusa2 (JAXA), embarked on a journey to two primitive asteroids in order to collect samples from their surface. The carbonaceous-type asteroid (162173) Ryugu was the target of the Hayabusa2 mission. The spacecraft performed two samplings, collecting surface and subsurface materials excavated by an artificial impactor, because the subsurface is more likely preserved from the alteration by space weathering processes. In December 2020, the sealed capsule containing 5.4 of precious samples returned to Earth. The capsule was opened in the Curation Facility (Sagamihara, Japan), a complex of clean chambers, in order to carry out a first analysis of the grains without exposing them to the terrestrial atmosphere.

A non-destructive spectral analysis of the whole collection was conducted in the Curation Facility. Then, some of the grains, up to several mm in size, were extracted from the Facility and analysed with other techniques, by international teams, in order to precisely characterise their mineralogy and their chemical composition. These analyses revealed that the samples are mainly composed of minerals formed by the aqueous alteration at low temperature (~40°C) of Ryugu’s parent body. The detection of rare anhydrous minerals reveals that some regions in the parent body were preserved from extensive aqueous alteration. Moreover, the analyses of the samples show that space weathering modified the physical and chemical properties of the particles exposed to space environment at the surface of the asteroid. The closest meteoritical analogs of Ryugu samples are CI chondrites, a class of meteorites probably originating from carbonaceous asteroids. However, some of the spectral and compositional differences between them suggest that CI chondrites could have been partly contaminated by terrestrial contamination. Thus, the asteroid samples are the most pristine primitive materials in our collections.

The capsule of the OSIRIS-REx spacecraft, containing the samples from (101955) Bennu, landed in the Utah desert in September 2023, and was then transferred to the Johnson Space Center at Houston. Analysis of Bennu samples is underway, and initial results suggest that Bennu, like Ryugu, contains hydrated minerals and organic matter. The laboratory characterization of these two asteroids will represent a major advancement in understanding the composition of our primitive solar system and its evolution.

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.