The dark mass concentration in the central parsec of the Milky Way

We report similar to 1 '' resolution K-band (2 mu m) imaging spectroscopy of the central parsec of our Galaxy. The derived radial velocities for 223 early- and late-type stars probe the nuclear mass distribution to spatial scales of 0.1 pc. We find a statistically very significant 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 counter-rotation. Fitting simultaneously the observed projected surface densities and velocity dispersions, we derive the intrinsic volume densities and radial velocity dispersions as a function of distance from the dynamic center for both types of stars. We then derive the mass distribution between 0.1 and 5 pc from the Jeans equation assuming an isotropic velocity held. Our analysis requires a compact central dark. mass 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 ratio can be reduced but not eliminated even if extreme anisotropic velocity destributions are considered. The dark mass cannot be a cluster of 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.