Rapid growth of seed black holes in the early universe by supra-exponential accretion
arXiv:1408.1718 · doi:10.1126/science.1251053
Abstract
Mass accretion by black holes (BHs) is typically capped at the Eddington rate, when radiation's push balances gravity's pull. However, even exponential growth at the Eddington-limited e-folding time t_E ~ few x 0.01 billion years, is too slow to grow stellar-mass BH seeds into the supermassive luminous quasars that are observed when the universe is 1 billion years old. We propose a dynamical mechanism that can trigger supra-exponential accretion in the early universe, when a BH seed is trapped in a star cluster fed by the ubiquitous dense cold gas flows. The high gas opacity traps the accretion radiation, while the low-mass BH's random motions suppress the formation of a slowly-draining accretion disk. Supra-exponential growth can thus explain the puzzling emergence of supermassive BHs that power luminous quasars so soon after the Big Bang.
Some typos corrected and minor stylistic changes to conform with final printed version. 18 pages (main article and supplementary materials) and 3 figures. First appeared in Science Express: http://www.sciencemag.org/content/early/2014/08/06/science.1251053. Final printed version: T. Alexander, P. Natarajan, Science, 12 September 2014, Vol. 345 no. 6202 pp. 1330-1333