The Bulge Radial Velocity Assay (BRAVA). I. Sample Selection and a Rotation Curve

Results from the ongoing Bulge Radial Velocity Assay (BRAVA) are presented. BRAVA uses M red giant stars, selected from the 2MASS catalog to lie within a bound of reddening-corrected color and luminosity, as targets for the Cerro Tololo Inter-American Observatory 4 m Hydra multiobject spectrograph. Three years of observations investigate the kinematics of the Galactic bulge major (-[image]) and minor (-[image]) axes with [image]3300 radial velocities from 32 bulge fields and one disk field. We construct a longitude-velocity plot for the bulge stars and find that, contrary to previous studies, the bulge does not rotate as a solid body; from -[image] the rotation curve has a slope of roughly 100 km s super(-1 ) kpc super(-1) and flattens considerably at greater l, reaching a maximum rotation of 75 km s super(-1). We compare our rotation curve and velocity dispersion profile both to the self-consistent model of Zhao and to N-body models; neither fits both our observed rotation curve and velocity dispersion profile. We place the bulge on the plot of [image] vs. epsilon and find that the bulge lies near the oblate rotator line and very close to the parameters of NGC 4565, an edge-on spiral galaxy with a bulge similar to that of the Milky Way. We find that our summed velocity distribution of bulge stars appears to be sampled from a Gaussian distribution, with [image] km s super(-1) for our full data set. Two candidate cold streams are not confirmed with additional data.