Radial Velocities of Stars in the Galactic Center
Abstract
We present the results of near-infrared slit scan observations of the inner parsec of the Galactic center in two epochs separated by 6 years. Using the CO band head absorption features and He I emission/absorption lines, we acquire the accurate measurements of the radial velocities and accelerations of both early and late type stars in the region. The velocity distribution of the late type stars has an approximate Gaussian shape with its center at 10 km/s and a standard deviation > 85 km/s, which suggests that the motion of the population is nearly relaxed through collisions. We estimate the central black hole mass to be 3.3 ± 0.7 million solar masses using the BT projected mass estimator based on an isotropic system. Both the surface density profile and the velocity dispersion of the late type stars suggest that a low stellar density at the very center of the region. There is no indication that the motions of the early type stars are relaxed. However, the early population shows systematic rotation around Sgr A*, in contrast to that no obvious figure rotation was found for the late type stars. The early type stars can be divided into two groups based on the widths of the observed He I emission/absorption lines. Spectral and kinematical differences between two groups of stars suggest that they belong to different dynamical structures which were formed at the same time millions years ago. Moreover, the accelerations of majority of the early type stars exceed the highest value allowed by pure circular motions, suggesting that the motions of these stars deviate from circular orbital motions around the Galactic center.
- Publication:
-
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AAS...211.1405Z