HALO7D II: The Halo Velocity Ellipsoid and Velocity Anisotropy with Distant Main Sequence Stars

Understand

The Halo Assembly in Lambda-CDM: Observations in 7 Dimensions (HALO7D) dataset consists of Keck II/DEIMOS spectroscopy and Hubble Space Telescope-measured proper motions of Milky Way (MW) halo main sequence turnoff stars in the CANDELS fields.

• In this paper, the second in the HALO7D series, we present the proper motions for the HALO7D sample.
• We discuss our measurement methodology, which makes use of a Bayesian mixture modeling approach for creating the stationary reference frame of distant galaxies.
• Using the 3D kinematic HALO7D sample, we estimate the parameters of the halo velocity ellipsoid, $\langle v_{\phi} \rangle, \sigma_r, \sigma_{\phi}, \sigma_{\theta}$, and the velocity anisotropy $\beta$.