We present results from K band slit scan observations of a \sim 20 ^ { \prime \prime } \times 20 ^ { \prime \prime } region of the Galactic center ( GC ) in two separate epochs more than five years apart .
The high resolution ( R = \frac { \lambda } { \Delta \lambda } { \geq } 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 \sim 2.2935 \mu m and the He I lines at \sim 2.0581 \mu m and \sim 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 \sim -7.8 \pm 10.3 km s ^ { -1 } and a standard deviation \sim 113.7 \pm 10.3 km s ^ { -1 } .
Although our statistics are dominated by the brightest stars , we estimate a central black hole mass of 3.9 \pm 1.1 \times 10 ^ { 6 } M _ { \odot } , 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 .