Dynamics of Kicked and Accelerated Massive Black Holes in Galaxies

Abstract

A study is made of the behavior of massive black holes in disk galaxies that have received an impulsive kick from a merger or a sustained acceleration from an asymmetric jet. The motion of the gas, stars, dark matter, and massive black hole are calculated using the GADGET-2 simulation code. The massive black hole escapes the galaxy for kick velocities above about 600 km s−1 or accelerations above about 4 × 10−8 cm s−2 over timescales of the order of 108 yr. For smaller velocity kicks or smaller accelerations, the black hole oscillates about the center of mass with a frequency that decreases as the kick velocity or acceleration increases. The black hole displacements may give rise to observable nonaxisymmetries in the morphology and dynamics of the stellar and gaseous disk of the galaxy. In some cases the dynamical center of the galaxy is seen to be displaced toward the direction of the BH acceleration with a characteristic tongue-shaped extension of the velocity contours on the side of the galaxy opposite the acceleration.