Evidence of a Metal Rich Galactic Bar from the Vertex Deviation of the Velocity Ellipsoid

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 non-parametric 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 for kinematic subgroups, but there is a mild tendency for the vertical velocity dispersion σb to decrease with increasing metallicity. Subject headings: Galaxy: bulge — Galaxy: kinematics and dynamics – Galaxy: abundances