The dynamical matter density in the solar neighbourhood inferred from Gaia DR1

Understand

We determine the total dynamical density in the solar neighbourhood using the Tycho-Gaia Astrometric Solution (TGAS) catalogue.

• Astrometric measurements of proper motion and parallax of stars inform us of both the stellar number density distribution and the velocity distribution of stars close to the plane.
• Assuming equilibrium, these distributions are interrelated through the local dynamical density.
• For the first time, we do a full joint fit of the velocity and stellar number density distributions while accounting for the astrometric error of individual stars, in the framework of Bayesian Hierarchical Modelling.