Consequences of Gravitational Radiation Recoil

Coalescing binary black holes experience an impulsive kick from anisotropic emission of gravitational waves. Recoil velocities are sufficient to eject most coalescing black holes from dwarf galaxies and globular clusters, which may explain the apparent absence of massive black holes in these systems. Ejection from giant elliptical galaxies would be rare, but coalescing black holes are displaced from the center and fall back on a timescale of order the half-mass crossing time. Displacement of the black holes transfers energy to the stars in the nucleus and can convert a steep density cusp into a core. Radiation recoil calls into question models that grow supermassive black holes from hierarchical mergers of stellar-mass precursors. Subject headings: black hole physics — galaxies: nuclei — gravitation — gravitational waves