Nature vs Nurture: Three Dimensional MHD Simulations of Misaligned Embedded Circum-Single Disks within an AGN Disk

Abstract

Stellar mass black holes in the disks around active galactic nuclei (AGN) are promising sources for gravitational wave detections by LIGO/VIRGO. Recent studies suggest this environment fosters the formation and merger of binary black holes. Many of these studies often assumed a simple, laminar AGN disk without magnetic fields or turbulence. In this work, we present the first 3D magnetohydrodynamical simulations of circum-single disks around isolated and binary black holes in strongly magnetized, stratified accretion disks with turbulence driven by magneto-rotational instability. We simulated three scenarios with varying initial net-vertical magnetic field strengths: weak, intermediate, and strong. Our results show that weakly magnetized models produce circum-single disks aligned with the AGN disk's equatorial plane, similar to past hydrodynamic simulations. However, intermediate and strong magnetic fields result in randomly misaligned disks, contingent upon the availability of local ambient angular momentum within turbulent regions. Our findings emphasize the significant impact of ambient gas in the AGN disk on the inclination of circum-single disks, linked to magnetically induced inhomogeneity and angular momentum during disk formation. The presence of misaligned disks, both in single and binary black hole systems, could have profound implications for the long-term evolution of black hole spin and the inclination of the disk at the horizon scale.