Radial velocities of stars in the galactic center

We present results from K-band slit scan observations of a similar to 20 '' x 20 '' region of the Galactic center (GC) in two separate epochs more than 5 years apart. The high-resolution (R = lambda/Delta lambda >= 14,000) observations allow the most accurate radial velocity and acceleration measurements of the stars in the central parsec of the Galaxy. Detected stars can be divided into three groups based on the CO absorption band heads at similar to 2.2935 mu m and the He II lines at similar to 2.0581 and similar to 2.112, 2.113 mu m: cool, narrow-line hot, and broad-line hot. The radial velocities of the cool, late-type stars have approximately a symmetrical distribution with its center at similar to-7.8 +/- 10.3 km s(-1) and a standard deviation similar to 113.7 +/- 10.3 km s(-1). Although our statistics are dominated by the brightest stars, we estimate a central black hole mass of (3.9 +/- 1.1) x 10(6) M-circle dot, consistent with current estimates from complete orbits of individual stars. Our surface density profile and the velocity dispersion of the late-type stars support the existence of a low-density region at the Galactic center suggested by earlier observations. Many hot, early-type stars show radial velocity changes higher than maximum values allowed by pure circular orbital motions around a central massive object, suggesting that the motions of these stars greatly deviate from circular orbital motions around the Galactic center. The correlation between the radial velocities of the early-type He I stars and their declination offsets from Sagittarius A* suggests that a systematic rotation is present for the early-type population. No figure rotation around the Galactic center for the late-type stars is supported by the new observations.