Accretion onto Intermediate-mass Seed Black Holes in Primordial Galaxies

The origin of the supermassive black holes that power the most distant quasars observed is largely unknown. One hypothesis is that they grew rapidly from intermediate-mass seeds (~100 M_sun) left by the first stars. However, some previous studies argued that accretion onto these black holes was too low to build up the mass due to strong suppression by radiative feedback. Here, we re-exam the accretion process of such a black hole embedded in a primordial gas cloud, by considering a wide range of physical and numerical parameters not explored before. We find that, while radiative heating and pressure indeed suppress accretion effectively, self-gravity of the gas eventually overcomes the feedback effects and boosts the accretion to the Eddington rate after one free-fall timescale of the cloud. Moreover, for a given black hole mass, there exists a critical density above which the accretion can reach Eddington limit. Furthermore, we find a universal correlation between black hole accretion rate and ambient gas density, which may serve as a realistic recipe for black hole growth in simulations.