The DESI collaboration (Dark Energy Spectroscopic Instrument) confirmed its groundbreaking results on dynamical dark energy through the largest 3-dimensional Universe map it observed. This talk highlights how DESI’s Baryon Acoustic Oscillation (BAO) measurements from Data Release 2 further challenge the ΛCDM paradigm, the standard cosmology for the past 30 years. The second part of this talk ...
In this talk, I will present the 4-metre Multi-Object Spectroscopic telescope as well as the recent news related to the on-going Science Phase Verification which aims to make different tests for all 4MOST science cases. I will in a second time present in more details the Cosmology Redshift Survey, especially the Bright Galaxies and Luminous Red Galaxies samples, as well as the quality checks an...
The tidal disruption of a star by a supermassive black hole and consequent accretion can lead to a transient electromagnetic flare in multiple bands. However, the origin of the detected emission from such tidal disruption events (TDEs) remains an open question. In this talk, I will discuss the potential emission mechanisms in TDEs during accretion disk formation, implied by series of 3D radiati...
Angular momentum is a key quantity linking the formation of galaxies to the dynamics of the cosmic web. Building on a series of recent observational and theoretical works, this talk will present a picture of how angular momentum is generated, transported and reprocessedacross scales—from megaparsec-scale filaments, through galaxy clusters, down to individual galaxies. I will first show how lar...
I present the first three-dimensional (3D), full-sky dust map that reveals variations in the extinction curve, parameterized by R(V). Using Gaia XP spectra, we measure extinction curves for over 130 million stars—more than two orders of magnitude more than previously available—enabling us to trace dust properties across the Milky Way with unprecedented detail. Surprisingly, trends in this map...
The Trapezium Cluster in Orion teaches us that massive stars often form together in compact systems—but how such dense OB groupings are assembled remains an open question. In this talk, I will present high-resolution observations with the Atacama Large Millimeter/submillimeter Array (ALMA) that reveal an exceptionally young, deeply embedded massive quadruple OB system in the making. The four m...
the past two decades, large-scale numerical simulations on parallel CPU clusters have been crucial for our theoretical understanding of star formation and stellar feedback. As modern supercomputers increasingly pivot toward GPU-dominated architectures, it has become essential to redesign our simulation tools to this new architecture in order to scale up these simulations. In this talk, I will g...
I will show that the low-mass stellar mass function in the Milky Way halo using a clean sample of metal-poor main-sequence stars from Gaia DR3 BP/RP (XP) spectra within 1 kpc. Combining probabilistic kinematic halo selection with XP-based [Fe/H] calibrated to SDSS-V/APOGEE, and a forward model with effective volumes, we find that below 0.5 solar mass the halo MF changes strongly with metallicit...
The Dark Energy Spectroscopic Instrument (DESI) has constructed the largest 3D map of galaxies and quasars to date, spanning the nearby Universe to a redshift of over 3. Recently, DESI has released cosmological measurements from its third-year (Y3) data, revealing evidences of dynamic dark energy. In this talk, I will review the DESI results, discuss potential problems and future developments.H...
Notoriously difficult to constrain with observations and physically intricate to model in simulations, the non-thermal physics of cosmic rays (CRs) and magnetic fields (B-fields), and their effects on galaxies, remain mostly elusive. The study of these processes is timely and scientifically exigent. Current simulations are able to evolve CRs with magnetic fields in tandem with feedback from sta...