Jets in magnetically arrested hot accretion flows: geometry, power, and black hole spin-down

Abstract

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 ≳ 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 100GM/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* ≲ 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.

The Formation of Intermediate-mass Black Holes in Galactic Nuclei

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A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows

“…These simulations were run for 100,000 GM/c 3 to study the effects of long-timescale trends. They form model set "C" and have been studied in Narayan et al (2022).…”

First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole

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