AAS 197, January 2001
Session 21. AGN Kinematics
Oral, Monday, January 8, 2001, 10:30am-12:00noon, Pacific One

## [21.01] Supermassive Black-Hole Binaries in Merging Cusps''

M. Milosavljevic, D. Merritt (Rutgers University)

We present N-body simulations of the formation and evolution of supermassive black-hole binaries in galactic nuclei. Initial conditions are drawn from a tree-code simulation of the merger of two spherical galaxies containing central point masses and \rho~r-2 central density cusps. Once the two black holes form a bound pair at the center of the merged galaxies, the evolution is continued using the Aarseth/Spurzem parallel tree code {\tt NBODY6++} at much higher resolution. Immediately following the formation of a hard black-hole binary, the density cusp of the merged galaxies is nearly homologous to the cusps in the initial galaxies. However the central density decreases rapidly as the binary black hole ejects stars which pass near to it, reducing the slope of the cusp from ~ r-2 to ~r-1. When the distance between the black holes becomes comparable to the average stellar separation in the cusp, the binary begins to wander about the center while engaging in hard encounters with stars on radial orbits that are ejected at high speed. Ejection induces further shrinking of the binary at a decreasing rate. We discuss the dynamics of black hole binaries in the limit of large N, appropriate to real galactic nuclei, and discuss the possibility that supermassive black hole binaries can survive over cosmological times.