2006/11/14 by M. Soto, Mario Soto, R. Michael Rich +3 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Bulge #Ellipsoid #Flattening #Population #Pulsars and Gravitational Waves Research #Radial velocity #Standard deviation #Stars #Stellar, planetary, and galactic studies #Velocity dispersion #Vertex (graph theory) #astro-ph
paper · pdf · doi:10.1086/521098
4 pages, ApJ Letters, submitted
arxiv created 2006/11/14 · openalex publication_date 2007/07/27 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We combine radial velocities, proper motions, and low-resolution abundances for a sample of 315 K and M giants in the Baade's window ( l , b ) = (0.9°, -4°) Galactic bulge field. The velocity ellipsoid of stars with [Fe/H] > -0.5 dex shows a vertex deviation in the plot of radial versus transverse velocity, consistent with that expected from a population with orbits supporting a bar. We demonstrate that the significance of this vertex deviation, using nonparametric rank correlation statistic, is >99%. The velocity ellipsoid for the metal-poor ([FeH] < -0.5) part of the population shows no vertex deviation and is consistent with an isotropic, oblate rotating population. We find no evidence of kinematic subgroups, but there is a mild tendency for the vertical velocity dispersion σ b to decrease with increasing metallicity.