Intermediate-mass Black Holes’ Effects on Compact Object Binaries

Abstract

Abstract Although their existence is not yet confirmed observationally, intermediate-mass black holes (IMBHs) may play a key role in the dynamics of galactic nuclei. In this paper, we neglect the effect of the nuclear star cluster itself and investigate only how a small reservoir of IMBHs influences the secular dynamics of stellar-mass black hole binaries, using N-body simulations. We show that our simplifications are valid and that the IMBHs significantly enhance binary evaporation by pushing the binaries into the Hill-unstable region of parameter space, where they are separated by the supermassive black hole’s tidal field. For binaries in the S-cluster region of the Milky Way, IMBHs drive the binaries to merge in up to 1%–6% of cases, assuming five IMBHs within 5 pc of mass 104 each. Observations of binaries in the Galactic center may strongly constrain the population of IMBHs therein.