SCYON Abstract

Received on December 19 2008

A New Secular Instability of Eccentric Stellar Disks Around Supermassive Black Holes, with Application to the Galactic center

Authors	Ann-Marie Madigan, Yuri Levin and Clovis Hopman
Affiliation	Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden
Submitted to	Astrophysical Journal
Contact	madigan@strw.leidenuniv.nl
URL	http://arxiv.org/abs/0812.3395
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Abstract

We identify a new secular instability of eccentric stellar disks around supermassive black holes. We show that retrograde precession of the stellar orbits, due to the presence of a stellar cusp, induces coherent torques that amplify deviations of individual orbital eccentricities from the average, and thus drive all eccentricities away from their initial value. We investigate the instability using N-body simulations, and show that it can drive individual orbital eccentricities to significantly higher or lower values on the order of a precession time-scale. This physics is relevant for the Galactic center, where massive stars are likely to form in eccentric disks around the SgrA* black hole. We show that the dynamical evolution of such a disk results in several of its stars acquiring high (1-e << 0.1) orbital eccentricity. Binary stars on such highly eccentric orbits would get tidally disrupted by the SgrA* black hole, possibly producing both S-stars near the black hole and high-velocity stars in the Galactic halo.