Feedback Limits Rapid Growth of Seed Black Holes at High Redshift

Abstract

Seed black holes formed in the collapse of Population III stars have been invoked to explain the presence of supermassive black holes at high redshift. It has been suggested that a seed black hole can grow up to 10⁵-10⁶ M_☉ through highly super-Eddington accretion for a period of ~10⁶-10⁷ yr at redshift z = 20-24. We studied the feedback of radiation pressure, Compton heating, and outflow during the seed black hole growth. It is found that its surrounding medium fueled to the seed hole is greatly heated by Compton heating. For a supercritical accretion onto a 10³ M_☉ seed hole, a Compton sphere (with a temperature ~10⁶ K) will be formed on a timescale of 1.6 × 10³ yr so that the hole is only supplied by a rate of 10^-3 of the Eddington limit from the Compton sphere. The kinetic feedback of the strong outflow will heat the medium at a large distance from the black hole; this leads to a dramatic decrease of the outer Bondi accretion onto the black hole and avoids the accumulation of the matter. The highly supercritical accretion will be rapidly halted by the strong feedback. The seed black hole hardly grows up at the very early universe unless the strong feedback can be avoided.