Description Studies Precomputed Catalogs


The Besançon Galaxy Model (BGM) is a stellar population synthesis model (e.g., Robin et al. 2003; Czekaj et al. 2014; Lagarde et al. 2017) that takes into account scenarios for the formation and evolution of the Galaxy, the theory of stellar formation and evolution, models of stellar atmospheres, as well as constraints on galactic dynamics, in order to provide a coherent image of the Galaxy with respect to the available observations. The simulations carried out with the BGM take into account the effects of the instrument's selection function, as well as observational biases. Four populations of stars are considered: the thin disc, the thick disc, the bulge and the halo, each with a specific density distribution. The stellar content of each population is modelled using an initial mass function and a star formation history, which differ from one population to another. Stellar evolution models are used to deduce (at current age) the properties of each star (mass, age, temperature, gravity, metallicity, abundances), which are used to calculate the observed properties using stellar atmosphere models and a 3D extinction map of the Galaxy. A Galactic dynamics model is then used to calculate the radial velocities and proper motions. This method is very effective for characterising the different stellar populations in the Galaxy (e.g., Reylé et al. 2009, Robin et al. 2014, Amores et al. 2017, Lagarde et al 2021), for constraining SFH and the disk IMF (Czekaj et al. 2014, Mor et al. 2018, 2019), and for the formation scenarios of the different stellar populations (Lagarde et al 2021).

Scientific studies done with the BGM

The stellar population synthesis model is useful for a variety of studies in different fields of astrophysics. I develop and use the Besançon model :

  • to constrain the physics of transport processes occurring in stars (see Lagarde N., et al. 2017, A&A, 601, A27, Lagarde N., et al.2019, A&A, 621, A24 and Part 1 of "Stellar population Synthesis")

  • to provide clues to a better understanding of the formation and evolution of our Galaxy and the stellar populations that make it up (see Lagarde N., et al. 2021 A&A, 654, A13 and Part 2 of "Stellar population Synthesis")

  • Finally, it should be noted that the BGM 2.0 is not only useful for stellar and Galactic evolution (my main research themes). Indeed, a better understanding of stars provides constraints on planet formation, on their properties and their environment, as well as on the location of the habitable zone, providing key constraints for improving models of planetary formation. In two papers in collaboration with specialists in the formation of planets and small solar system bodies, the BGM 2.0 was used to study the properties of 'planet building blocks' according to the galactic population to which their host star belongs. These studies, using both my stellar evolution models and the BGM 2.0 that I developed, are crucial to understanding the formation and characterisation of exoplanets.

    • Cabral N, Lagarde N., et al.2019, A&A, 622, A49
      “Chemical composition of planet building blocks as predicted by stellar population synthesis”
    • Cabral et al. 2023 A&A 673 A117
      “ How the origin of stars in the Galaxy impacts the composition of planetary building blocks ”

  • Precomputed Mock catalogs

    under construction