2021/08/31 by Ramesh Narayan, Andrew Chael, Koushik Chatterjee +2 · 2 citations
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stac285
Accepted by MNRAS 2022 January 26. Received 2022 January 26; in original form 2021 August 27
arxiv created 2022/01/27 · arxiv updated 2022/02/16
We present the results of nine simulations of radiatively-inefficient magnetically arrested disks (MADs) across different values of the black hole spin parameter a_*: -0.9, -0.7, -0.5, -0.3, 0, 0.3, 0.5, 0.7, and 0.9. Each simulation was run up to t \gtrsim 100,000 GM/c3 to ensure disk inflow equilibrium out to large radii. We find that the saturated magnetic flux level, and consequently also jet power, of MAD disks depends strongly on the black hole spin, confirming previous results. Prograde disks saturate at a much higher relative magnetic flux and have more powerful jets than their retrograde counterparts. MADs with spinning black holes naturally launch jets with generalized parabolic profiles whose widths vary as a power of distance from the black hole. For distances up to 100 GM/c2, the power-law index is k ≈ 0.27-0.42. There is a strong correlation between the disk-jet geometry and the dimensionless magnetic flux, resulting in prograde systems displaying thinner equatorial accretion flows near the black hole and wider jets, compared to retrograde systems. Prograde and retrograde MADs also exhibit different trends in disk variability: accretion rate variability increases with increasing spin for a_*>0 and remains almost constant for a_*\lesssim 0, while magnetic flux variability shows the opposite trend. Jets in the MAD state remove more angular momentum from black holes than is accreted, effectively spinning down the black hole. If powerful jets from MAD systems in Nature are persistent, this loss of angular momentum will notably reduce the black hole spin over cosmic time.