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

Prasenjit Saha (1), Geoffrey V. Bicknell (2), and Peter J. McGregor (1)

(1) Mt. Stromlo & Siding Spring Observatories, Weston PO, ACT 2611, Australia; \hfill\break email: saha@mso.anu.edu.au, peter@mso.anu.edu.au (2) ANU Astrophysical Theory Centre. Australian National University, Canberra, ACT 0200, Australia. email: geoff@wintermute.anu.edu.au. The ANUATC is operated jointly by the Mt. Stromlo and Siding Spring Observatories and the School of Mathematical Sciences.

Paper: ApJ, in press

EPrint Server: astro-ph/9604153


We reanalyze published kinematic and photometric data for the cool star population in the central 10 pc (240'') 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 \lelt;=q 1 outside a radius of 0.8 pc to > 2 at 0.35 pc. This behavior cannot be due to the presence of a central massive black hole. We suggest that such a varying M/L_K may be due to an increasing concentration of stellar remnants towards the Galactic center. Our derived mass-radius curve confirms the existence of ~ 3 * 10^6 \> \msolar within 0.35 pc of the Galactic center, and ~ 1.5 * 10^6 \> \msolar within 0.2 pc. However, the latter estimate is subject to the uncertain distribution of cool stars in this region. We also consider the dynamics of the hot star population close to the Galactic center and show that the velocity dispersion of the He I stars and the surface brightness distribution of the hot stars are consistent with the mass distribution inferred from the cool stars.

Preprints available from the authors at gvb@maths.anu.edu.au , or the raw TeX (no figures) if you click here.

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