title: Rapid growth of seed black holes in the early universe by supra-exponential accretion.
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 × 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 bound 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.
authors.affiliation: Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel. tal.alexander@weizmann.ac.il.
authors.forename: Tal
authors.initials: T
authors.lastname: Alexander
authors.affiliation: Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511, USA.
authors.forename: Priyamvada
authors.initials: P
authors.lastname: Natarajan