Le 22 décembre 2017
De 10h30 à 12h00

Max Gronke UC Santa Barbara   The Lyman-alpha (Lya) of neutral hydrogen is the most prominent...

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

Le 24 novembre 2017
De 10h30 à 12h00

Giacomo Monari

AIP Potsdam

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 all stars, in the framework of Bayesian Hierarchical Modelling. We use a sample of stars whose distance extends to approximately 160 pc from the Sun. We find a local matter density of 0.119 Msun/pc^3, as the median to the posterior distribution. We find the Sun's position above the Galactic plane to be Zsun = 15.3 pc, and the Sun's velocity perpendicular to the Galactic plane to be Wsun = 7.19 km/s.

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