THE DARK MASS CONCENTRATION IN THE CENTRAL PARSEC OF THE MILKY-WAY

We report similar to 1 '' resolution K-band (2 mu m) imaging spectrosc opy of the central parsec of our Galaxy. The derived radial velocities for 223 early- and late-type stars probe the nuclear mass distributio n to spatial scales of 0.1 pc. We find a statistically very significan t increase of projected stellar velocity dispersion from about 55 km s (-1) at p similar to 5 pc to 180 km s(-1) at p similar to 0.1 pc. The stars are also rotating about the dynamic center. The late-type stars follow general Galactic rotation, while the early-type stars show coun ter-rotation. Fitting simultaneously the observed projected surface de nsities and velocity dispersions, we derive the intrinsic volume densi ties and radial velocity dispersions as a function of distance from th e dynamic center for both types of stars. We then derive the mass dist ribution between 0.1 and 5 pc from the Jeans equation assuming an isot ropic velocity held. Our analysis requires a compact central dark. mas s of 2.5-3.2 x 10(6) M., at 6-8 sigma significance. The dark mass has a density of 10(9) M. pc(-3) or greater and a mass to 2 pm luminosity of greater than or equal to 100. The increase in mass-to-luminosity ra tio can be reduced but not eliminated even if extreme anisotropic velo city destributions are considered. The dark mass cannot be a cluster o f solar mass remnants (such as neutron stars). It is either a compact cluster of 10-20 M. black holes or a single massive black hole.