Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation
Abstract
We present new results from BRAVA, a large-scale radial velocity survey of the Galactic bulge, using M giant stars selected from the Two Micron All Sky Survey catalog as targets for the Cerro Tololo Inter-American Observatory 4 m Hydra multi-object spectrograph. The purpose of this survey is to construct a new generation of self-consistent bar models that conform to these observations. We report the dynamics for fields at the edge of the Galactic bulge at latitudes b = -8° and compare to the dynamics at b = -4°. We find that the rotation curve V(r) is the same at b = -8° as at b = -4°. That is, the Galactic boxy bulge rotates cylindrically, as do boxy bulges of other galaxies. The summed line-of-sight velocity distribution at b = -8° is Gaussian, and the binned longitude-velocity plot shows no evidence for either a (disk) population with cold dynamics or for a (classical bulge) population with hot dynamics. The observed kinematics are well modeled by an edge-on N-body bar, in agreement with published structural evidence. Our kinematic observations indicate that the Galactic bulge is a prototypical product of secular evolution in galaxy disks, in contrast with stellar population results that are most easily understood if major mergers were the dominant formation process.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2009
- DOI:
- arXiv:
- arXiv:0908.1109
- Bibcode:
- 2009ApJ...702L.153H
- Keywords:
-
- Galaxy: bulge;
- Galaxy: kinematics and dynamics;
- stars: kinematics;
- stars: late-type;
- techniques: radial velocities;
- Astrophysics - Galaxy Astrophysics
- E-Print:
- 6 pages, 5 figures Received 2009 May 2