A Varying Mass-To-Light Ratio in the Galactic Center Cluster?

Abstract

We reanalyze published kinematic and photometric data for the cool star population in the central 10 pc (240 arcsec) of the Galaxy, while (a) isolating the photometric data appropriate to this population, and (b) properly allowing for projection effects. Under the assumptions that the system is spherical and isotropic, we find that M/L_K varies from <=1 outside a radius of 0.8 pc to >2 at 0.35 pc. We suggest that such a varying M/L_K could be due to an increasing concentration of stellar remnants towards the Galactic center. Our derived mass-radius curve confirms the existence of ~3x10^6 M_sol within 0.35 pc of the Galactic Center, and ~1.5x10^6 M_sol with 0.2 pc. However, the latter estimate is subject to the uncertain distribution of cool stars in the region. We also consider the dynamics of the hot star population close to the Galactic center and show that the velocity dispersion of He I stars and the surface brightness distribution of the hot stars are consistent with the mass distribution inferred from cool stars.