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T. S. Statler, R. M. Salow (Ohio Univ.)
The ``double nucleus'' of the Andromeda Galaxy (M31) is best explained by a model in which the optically fainter peak P2 contains the stellar cusp around the central black hole (BH), and the optically brighter peak P1 is a statistical density enhancement in an eccentric stellar disk with radially declining eccentricity. We construct two-dimensional dynamical models for such disks. The disk is fixed in a frame rotating with constant precession speed, and consists of stars on quasi-periodic orbits whose parents are periodic orbits explicitly integrated in the total potential. The quasi-periodic orbits are approximated by distributions of Kepler ellipses dispersed in eccentricity and orientation about the parent orbits. The models are fitted to the extant photometric and stellar kinematic data from HST and the CFHT, to constrain the mass and location of the BH and the parameters of the nuclear disk. We find the BH mass to be (5.62 ±0.66) \times 107\ M\odot, consistent with that implied by the observed correlation between BH mass and host galaxy velocity dispersion. The best-fit location for the BH matches that of the ultraviolet-bright peak within P2 to within 0.02 arcseconds. The disk self-gravity drives a precession with a period of (2.7 ±0.3) \times 104 years. The eccentricity profile gives rise to multi-peaked line-of-sight velocity distributions near the BH, which can be used as sensitive discriminants of disk structure.
This work was supported by NSF CAREER grant AST-9703036 and Space Telescope Science Institute grant HST-GO-08589.02-A.
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Bulletin of the American Astronomical Society, 36 #2
© 2004. The American Astronomical Soceity.