# A Non-Parametric Estimate of the Mass of the Central Black Hole in the Galaxy

## Dalia Chakrabarty(1,2), Prasenjit Saha(3)

(1) Department of Physics (Astrophysics), University of Oxford, Keble Road, Oxford OX1 3RH, UK

(2) Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 3RH, UK

(3) Astronomy Unit, School of Mathematical Sciences, Queen Mary and Westfield College, London E1 4NS, UK

### Paper: ApJ, in press (July 2001)

**Abstract:**
We estimate the mass of the central black hole in our Galaxy from
stellar kinematical data published by Ghez et al. (1998) and
Genzel et al. (2001). For this we develop a method, related to
Merritt (1993), for non-parametrically reconstructing the mass profile
and the stellar distribution function in the central region of the
Galaxy from discrete kinematic data, including velocity errors.
Models are searched using the Metropolis algorithm. We assume that the
mass distribution is spherical and the stellar velocity distribution
is isotropic, and devise a test of this assumption. From proper
motions we obtain an enclosed mass of 2.0+/-0.7*10^{6}
M_o within the inner 0.0044pc, from radial velocities we
obtain a mass of 2.2^{+1.6}_-1.0*10^{6}M_o within
0.046pc and from three-dimensional velocities we obtain
1.8^{+0.4}_-0.3*10^{6}M_o within 0.046pc.

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