Abstract
Black hole (BH) spin can play an important role in galaxy evolution by controlling the amount of energy and momentum ejected from near the BH into the surroundings. We focus on radiatively inefficient and geometrically thick magnetically arrested disks (MADs) that can launch strong BH-powered jets. With an appropriately chosen adiabatic index, these systems can describe either the low-luminosity or highly super-Eddington BH accretion regimes. Using a suite of 3D general relativistic magnetohydrodynamic simulations, we find that for any initial spin, an MAD rapidly spins down the BH to the equilibrium spin of 0 < a eq ≲ 0.1, very low compared to a eq = 1 for the standard thin luminous (Novikov-Thorne) disks. This implies that rapidly accreting (super-Eddington) BHs fed by MADs tend to lose most of their rotational energy to magnetized relativistic outflows. In an MAD, a BH only needs to accrete 20% of its own mass to spin down from a = 1-0.2. We construct a semi-analytic model of BH spin evolution in MADs by taking into account the torques on the BH due to both the hydrodynamic disk and electromagnetic jet components, and find that the low value of a eq is due to both the jets slowing down the BH rotation and the disk losing a large fraction of its angular momentum to outflows. Our results have crucial implications for how BH spins evolve in active galaxies and other systems such as collapsars, where the BH spin-down timescale can be short enough to significantly affect the evolution of gamma-ray emitting BH-powered jets.
| Original language | English (US) |
|---|---|
| Article number | 82 |
| Journal | Astrophysical Journal |
| Volume | 960 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 1 2024 |
Funding
We thank Ryan Hickox and Zoheyr Doctor for their helpful discussions. We thank the referee for their helpful comments on the manuscript. B.L. acknowledges support from a National Science Foundation Graduate Research Fellowship under grant No. DGE-2234667. B.L. also acknowledges support by an Illinois Space Grant Consortium (ISGC) Graduate Fellowship supported by a National Aeronautics and Space Administration (NASA) grant awarded to the ISGC. J.J. and A.T. acknowledge support by the NSF AST-2009884 and NASA 80NSSC21K1746 grants. A.T. also acknowledges support by NSF grants AST-2107839, AST-1815304, AST-1911080, OAC-2031997, and AST-2206471. Support for this work was also provided by the National Aeronautics and Space Administration through Chandra Award Number TM1-22005X issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. We acknowledge support by the NSF through resources provided by NICS Kraken, where simulations were carried out, NICS Nautilus and TACC Frontera (Stanzione et al. ), where data were analyzed, and NCSA MSS and TACC Ranch, where data were backed up, under grants TG-AST100040 (TeraGrid), AST20011 (LRAC), and AST22011 (Pathways).
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science