A Nonparametric Estimate of the Mass of the Central Black Hole in the Galaxy

We estimate the mass of the central black hole in our Galaxy from stellarkinematical data published by Ghez et al. (1998) and Genzel et al. (2000). Forthis we develop a method, related to Merritt (1993), for non-parametricallyreconstructing the mass profile and the stellar distribution function in thecentral region of the Galaxy from discrete kinematic data, including velocityerrors. Models are searched using the Metropolis algorithm. We assume that themass distribution is spherical and the stellar velocity distribution isisotropic, and devise a test of this assumption. From proper motions we obtainan enclosed mass of $2.0\pm{0.7}\times10^6{\rm M}_{\odot}$ within the inner$0.0044\rm pc$, from radial velocities we obtain a mass of$2.2^{+1.6}_{-1.0}\times10^6{\rm M}_{\odot}$ within 0.046pc and fromthree-dimensional velocities we obtain $1.8^{+0.4}_{-0.3}\times10^6{\rmM}_{\odot}$ within 0.046pc.Comment: 27 pages, 8 figures, accepted for publication in the July issue of A