A binary supermassive black hole leaves an imprint on a galactic nucleus in the form of a “mass deficit,” a decrease in the mass of the nucleus due to ejection of stars by the binary. The magnitude of the mass deficit is in principle related to the galaxy’s merger history, but the relation has never been quantified. Here, highaccuracy N-body simulations are used to calibrate this relation. Mass deficits are shown to be Mde f ≈ 0.5M12, with M12 the total mass of the binary; the coefficient in this relation depends only weakly on M2/M1 or on the galaxy’s pre-existing density profile. Hence, after N mergers, Mde f ≈ 0.5N M• with M• the final (current) black hole mass. When compared with observed mass deficits, this result implies 1∼ < N ∼ < 3, in accord with hierarchical galaxy formation models. Implications for binary stalling radii, the origin of hyper-velocity stars, and the distribution of dark matter at the centers of galaxies are discussed.
Department, Program, or Center
School of Physics and Astronomy (COS)
David Merritt 2006 ApJ 648 976
RIT – Main Campus