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An Eccentric Disk Model for the Nucleus of M31

Scott Tremaine
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Abstract

The nucleus of M31 may be a thick eccentric disk, composed of stars traveling on nearly Keplerian orbits around a black hole or other dark compact object. This hypothesis reproduces most of the features seen in HST photometry of the center of M31; in particular the bright off-center source P1 is the apoapsis of the disk. An eccentric disk can also explain the rotation curve and asymmetric dispersion profile revealed by ground-based observations. The central object must be smaller than 1 pc so that the potential felt by the disk is nearly Keplerian. The disk eccentricity may be excited by a secular instability driven by dynamical friction from the bulge.

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Scott Tremaine. 1995-02-13. An Eccentric Disk Model for the Nucleus of M31. https://doi.org/10.1086/117548

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