Abstract
Context. Dynamically self-consistent galactic models are necessary for analysing and interpreting star counts, stellar density distributions, and stellar kinematics in order to understand the formation and the evolution of our Galaxy. Aims. We modify and improve the dynamical self-consistency of the Besançon Galaxy model in the case of a stationary and axisymmetric gravitational potential. Methods. Each stellar orbit is modelled by determining a Stäckel approximate integral of motion. Generalised Shu distribution functions (DFs) with three integrals of motion are used to model the stellar distribution functions. Results. This new version of the Besançon model is compared with the previous axisymmetric BGM2014 version and we find that the two versions have similar densities for each stellar component. The dynamically self-consistency is improved and can be tested by recovering the forces and the potential through the Jeans equations applied to each stellar distribution function. Forces are recovered with an accuracy better than one per cent over most of the volume of the Galaxy.
Highlights
The Besançon Galaxy model (Robin & Crézé 1986a,b; Bienaymé et al 1987; Marshall et al 2006; Reylé et al 2009; Robin et al 2012, 2014; Amôres et al 2017; Lagarde et al 2017, 2018) has been created to model the observed Galactic star counts, to allow predicted star counts, and to give insight on the structure, formation, and evolution of our Galaxy
This new version of the Besançon model is compared with the previous axisymmetric BGM2014 version and we find that the two versions have similar densities for each stellar component
The dynamically self-consistency is improved and can be tested by recovering the forces and the potential through the Jeans equations applied to each stellar distribution function
Summary
The Besançon Galaxy model (Robin & Crézé 1986a,b; Bienaymé et al 1987; Marshall et al 2006; Reylé et al 2009; Robin et al 2012, 2014; Amôres et al 2017; Lagarde et al 2017, 2018) has been created to model the observed Galactic star counts, to allow predicted star counts, and to give insight on the structure, formation, and evolution of our Galaxy. One way to achieve this goal consists in building dynamically self-consistent Galactic models that relate the kinematics and the number density for each stellar population through the collisionless Boltzmann equation under the hypothesis of stationarity Such models are based on explicit distribution functions (Ting et al 2013; Binney et al 2014; Bovy 2015; Bienaymé et al 2015; Binney & McMillan 2016; Vasiliev 2019) and these available models follow identical approaches (see a compilation by Sanders & Binney 2016) using Stäckel fits and fitting orbits with actions at the exception of Bienaymé et al (2015) who used analytic integrals of motion. We present a comparison of the previous BGM2014 version with this new one
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