Seminar by Marc del Alcázar on the topic of Besançon Galaxy model and Gaia

Seminar by Marc del Alcázar, from Universitat de Barcelona, on the topic of Besançon Galaxy model and Gaia.

Title: Assembling the BGM Puzzle: From CMD-Fitting to Dynamical Self-Consistency

Abstract: The Gaia mission provides an unprecedented combination of photometric, astrometric, and radial velocity information with which to constrain the structure and evolution of the Milky Way. We present a global strategy to improve the Besançon Galaxy Model (BGM) by connecting its stellar-population constraints with a dynamically self-consistent Galactic potential. Our approach combines three complementary tools within the BGM framework: BGM FASt, which derives the star formation history (SFH) and initial mass function (IMF) through colour-magnitude diagram fitting; BGM SKIn, which constrains the spatial and kinematic distributions using Gaia astrometry; and BGM Pot, which fits the rotation curve and computes the Galactic potential and dynamically self-consistent distribution functions. These components are iterated within the population-synthesis model to produce a self-consistent synthetic stellar catalogue. Applying the framework to the Gaia Catalogue of Nearby Stars (GCNS) yields an improved description of both stellar populations and their spatial and kinematic distributions. The recovered local SFH shows an enhancement in star formation approximately 2–6 Gyr ago, consistent with previous results. This work constitutes a holistic approach to BGM modelling and provides a flexible framework ready to exploit larger Gaia samples, jointly constrain the IMF and SFH, and prepare for the forthcoming Gaia DR4 data.