Joint Astrophysics Colloquium

Lemming Black Holes

M. Coleman Miller

University of Maryland

Black holes with billions of solar masses have been discovered at redshifts as high as z=7, when the universe was less than eight hundred million years old. Given the probable formation time of the first stars, this may not be enough time for the holes to grow from stellar-mass seeds via conventional pathways. Recently, we suggested a new scenario. In the redshift z>10 universe, mergers between galaxies that already had massive and dense stellar clusters would commonly bring in several times as much mass in gas as there was in stars. This has been shown in computer simulations to lead to instabilities that can shepherd the gas to the center of the clusters, leading to contraction of the clusters and subsequent destruction of their binaries. Without binary interactions to hold the clusters up, they can undergo core collapse, in which the central density becomes so high that initially unbound stellar-mass black holes merge with each other via the emission of gravitational radiation.