# A self-consistent dynamical model of the Milky Way disc set to Gaia data

**Authors:** A. C. Robin, O. Bienaymé, J. B. Salomon, C. Reylé, N. Lagarde, F. Figueras, R. Mor, J. G. Fernández-Trincado, J. Montillaud  
**arXiv:** [2208.13827](https://arxiv.org/abs/2208.13827)  
**Date:** 2022-08-29  
**Summary page:** https://www.summarizepaper.com/en/paper/2208.13827v1/

## Key points

- Comprehensive study on constructing a self-consistent dynamical model of the Milky Way disc
- Utilization of Besancon Galaxy Model to derive potential and compute distribution functions for disc stars
- Accurate modeling of stationary stellar discs through meticulous processes
- Use of Markov chain Monte Carlo (MCMC) techniques to fit free parameters to Gaia data
- Determination of velocity dispersion ellipsoid variations for sub-components based on galactic radii and vertical distances
- Obtaining density laws and radial scale lengths for thin and thick disc populations self-consistently
- Identification of features such as a flaring thin disc and distinct characteristics between old thin disc and thick disc components
- Suggestion of near-spherical symmetry in the dark matter halo within the Milky Way
- Derivation of Solar motion parameters with high precision, aligning with recent studies
- Development of a fully self-consistent gravitational potential providing an effective approximation of mass distribution within the galaxy

## Summary

This paper presents a comprehensive study on the construction of a self-consistent dynamical model of the Milky Way disc by fitting the gravitational potential to stellar kinematics and densities derived from Gaia data. The authors utilize the Besancon Galaxy Model to derive a potential and compute distribution functions for disc stars based on three integrals of motion. Their aim is to accurately model stationary stellar discs through meticulous processes. The resulting gravitational potential and stellar distribution functions are built in a self-consistent manner and adjusted to align with observations from Gaia. This is achieved using Markov chain Monte Carlo (MCMC) techniques to fit free parameters to parallax and proper motion distributions obtained from several sets of Gaia eDR3 data across different longitudes and latitudes. The study successfully determines the velocity dispersion ellipsoid and its variations for sub-components of different ages with respect to galactic radii (R) and vertical distances (z). Additionally, density laws and radial scale lengths for thin and thick disc populations are obtained self-consistently. Notably, the developed model reveals intriguing features such as a flaring thin disc, while distinct characteristics between the old thin disc and thick disc support the hypothesis that these components formed under separate scenarios due to an abrupt transition in density and kinematics. Furthermore, findings suggest that the dark matter halo exhibits near-spherical symmetry within the Milky Way. The authors also derive Solar motion parameters with high precision, showing good agreement with recent studies. The resulting fully self-consistent gravitational potential remains axisymmetric but provides an effective approximation of mass distribution within our galaxy. This model can serve as a valuable tool for future research endeavors, including orbit computations for real stars in the Milky Way. Overall, this study significantly advances our understanding of the dynamics and structure of our galaxy's disc based on state-of-the-art observational data analysis techniques.