Growth of Massive Black Holes at High-z via Accretion Predominantly Driven by Magnetic Outflows

Abstract

Luminous quasars powered by accreting supermassive black holes (SMBHs) have been found in the early universe at , which set a strong constraint on both the seed black hole (BH) mass and the rapid growth of the SMBHs. In this work, we explore how the SMBHs grow through Eddington-limited accretion driven predominantly by magnetic outflows. Most angular momentum and the released gravitational energy in the disk can be removed by magnetic outflows, therefore the mass-accretion rate of the BH can be high even if the disk is radiating at sub-Eddington luminosity. It is found that the SMBH with several billion solar masses discovered at may be grown through chaotic accretion predominantly driven by magnetic outflows from a stellar mass BH, when the disks are radiating at moderate luminosity (∼0.5 Eddington luminosity) with mild outflows. We find that most SMBHs are spinning at moderate values of spin parameter a * , which implies only a small fraction of quasars may have radio jets.