2008/07/24 by Christian Howard, Christian D. Howard, R. Michael Rich +5 · 6 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/592106
45 pages, 21 figures, 4 tables. Accepted for publication in the Astrophysical Journal on 24 July 2008
arxiv created 2008/07/24 · openalex publication_date 2008/11/17 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
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 (–10° < l < + 10°, b = − 4°) and minor (–6° < b < + 5°, -0.4° < l < 0.0°) axes with ~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 –4° < l < + 4° the rotation curve has a slope of roughly 100 km s −1 kpc −1 and flattens considerably at greater l , reaching a maximum rotation of 75 km s −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 V max /σ vs. 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 σ = 116 ± 2 km s −1 for our full data set. Two candidate cold streams are not confirmed with additional data.