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Abstract:
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We determine the total dynamical matter density of the galactic disk using astrometry from the Gaia mission. The dynamical matter density distribution is inferred in a framework of a Bayesian hierarchical model, which accounts for position and velocity of all individual stars, as well as the full error covariance matrix of astrometric observables, in a joint fit of the vertical velocity distribution and stellar number density distribution. This is done for eight separate data samples, with different cuts in observed absolute magnitude, each containing about 25,000 stars. The inference of the total matter density is model independent, in the sense that it does not rely on any underlying baryonic model. We infer a density distribution which is strongly peaked in the region close to the Galactic plane, for all eight stellar samples.
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