Gas accretion by star clusters and the formation of ultraluminous x-ray sources from cusps of compact remnants

Abstract

Here, we show that the overabundance of ultraluminous, compact X-ray sources associated with moderately young clusters in interacting galaxies such as the Antennae and the Cartwheel can be given an alternative explanation that does not involve the presence of intermediate mass black holes (IMBHs). We argue that gas density within these systems is enhanced by the collective potential of the cluster prior to being accreted onto the individual cluster members and, as a result, the aggregate X-ray luminosity arising from the neutron star cluster members can exceed > 1039 erg s-1. Various observational tests to distinguish between IMBHs and accreting neutron star cusps are discussed. © 2009. The American Astronomical Society. All rights reserved.