Validation of the Bond et al. (2010) SDSS-derived kinematic models for the Milky Way’s disk and halo stars with Gaia Data Release 3 proper motion and radial velocity data

¹ Departamento de Astronomía, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
² Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA
³ Faculty of Physics, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia
⁴ Department of Astronomy, University of Washington, Box 351580 Seattle, WA 98195, USA
⁵ Department of Astronomy and the DiRAC Institute, University of Washington, 3910 15th Avenue NE, Seattle, WA 98195, USA
e-mail: ivezic@uw.edu

Received: 18 February 2024
Accepted: 11 May 2024

Abstract

We validate the Bond et al. (2010, ApJ, 716, 1) kinematic models for the Milky Way’s disk and halo stars with Gaia Data Release 3 data. Bond et al. constructed models for stellar velocity distributions using stellar radial velocities measured by the Sloan Digital Sky Survey (SDSS) and stellar proper motions derived from SDSS and the Palomar Observatory Sky Survey astrometric measurements. These models describe velocity distributions as functions of position in the Galaxy, with separate models for disk and halo stars that were labeled using SDSS photometric and spectroscopic metallicity measurements. We find that the Bond et al. model predictions are in good agreement with recent measurements of stellar radial velocities and proper motions by the Gaia survey. In particular, the model accurately predicts the skewed non-Gaussian distribution of rotational velocity for disk stars and its vertical gradient, as well as the dispersions for all three velocity components. Additionally, the spatial invariance of velocity ellipsoid for halo stars when expressed in spherical coordinates is also confirmed by Gaia data at galacto-centric radial distances of up to 15 kpc.