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Session 79 - Special Objects in the Galaxy.
Oral session, Thursday, June 11

[79.02] A Massive Black Hole Within a Cluster of Compact Stellar Remnants: Possible Structure of Dark Mass Concentration at the Galactic Center

L. Ozernoy (CSI/GMU and GSFC/NASA)

The dynamical modelling of stellar velocities and proper motions in the Galactic center indicates an extended, nearly isothermal cluster of normal stars with a core radius of \sim0.5 pc as well as some dark matter, or DM (e.g. \left[^1\right]). I assume the DM in the innermost central region of the Galaxy consists of two major components: (i) an extended, although a highly concentrated, cluster of compact stellar remnants (CSRs), such as white dwarfs, neutron stars, and stellar black holes (*BHs), plus (ii) a point central mass, a massive black hole (MBH). The MBH could have formed either before the Galaxy formation (Scenario 1) or as a result ot the dynamical evolution of the stellar nucleus (Scenario 2). In Scenario 2, I explore whether the central part of the multi-mass system of CSRs, which supposedly consists mainly of *BHs, is in the state of a bounced core collapse. The bounce could occur as a result of heating produced by *BH binaries formed by three-body process \left[^2\right]. Then the DM cluster experiences a slow expansion accompanied by core oscillations. The central point mass -- a MBH -- could have formed during those oscillations. Its current mass is a sizeable fraction of that associated with the CSR cluster. The inferred density of stars wihin the central \sim 0.01 pc of the Galaxy is consistent with what would be expected if the core were in the post-bounced state of gravo-thermal oscillations. If further, higher resolution data on velocity dispersion v confirm an increase v\propto r^-1/2 toward smaller r, it would imply that the heating by *BH binaries was inefficient. This would imply a much larger ratio of MBH mass to that in CSRs and would be evidence in favor of Scenario 1, i.e. the primordial origin of the central MBH. \vspace0.05truein

References: \footnotesize \left[^1\right] Eckart, A. amp; Genzel, R. 1997, MNRAS 284, 576 \left[^2\right] Lee, H.M. 1995, MNRAS 272, 605

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