Fading Features Found in the Kinematics of the Far-Reaching Milky Way Stellar Halo

Abstract

We test the long-term kinematical stability of a Galactic stellar halo model, due to Kafle, et al. (2012), who study the kinematics of approximately 5000 blue horizontal branch (BHB) stars in the Sloan Digital Sky Survey (SDSS). The velocity dispersion $\sigma$ and anisotropy parameter $\beta$ of the stars have been determined as functions of Galactocentric radius, over the range $6<R_{\mathrm{GC}}<25$ kpc, and show a strong dip in the anisotropy profile at $R_{\mathrm{GC}}\sim 17$ kpc. By directly integrating orbits of particles in a 3-D model of the Galactic potential with these characteristics, we show that the $\sigma$ and $\beta$ profiles quickly evolve on a time scale of a $\mathrm{few}\times 10$ Myr whereas the density $\rho$ profile remains largely unaffected. We suggest that the feature is therefore transient. The origin of such features in the Galactic halo remains unclear.

Accepted for publication in MNRAS, 5 pages, 4 figures, 1 table

References in corpus (5)

• Two Stellar Components in the Halo of the Milky Way
• The stellar halo of the Galaxy
• Kinematics of the stellar halo and the mass distribution of the Milky Way using BHB stars
• Touching The Void: A Striking Drop in Stellar Halo Density Beyond 50 kpc
• Does SEGUE/SDSS indicate a dual Galactic halo?

Cited by in corpus (5)

• Constraints on the assembly history of the Milky Way's smooth, diffuse stellar halo from the metallicity-dependent, radially-dominated velocity anisotropy profiles probed with K giants and BHB stars using LAMOST, SDSS/SEGUE, and Gaia
• Probing the Galactic halo with RR Lyrae stars $-$ III. The chemical and kinematic properties of the stellar halo
• Galactic googly: the rotation-metallicity bias in the inner stellar halo of the Milky Way
• The Milky Way Revealed by Variable Stars I: Sample Selection of RR Lyrae stars, and Evidence for the Merger History
• Probing the Galactic halo with RR Lyrae stars -- IV. On the Oosterhoff dichotomy of RR Lyrae stars