Hydrodynamical Simulations of Black-Hole Binary Formation in AGN Disks by Jiaru Li et al. on Monday 21 November
We study the close encounters between two single black holes (BHs) embedded
in an AGN disk using a series of global 2D hydrodynamics simulations. We find
that when the disk density is sufficiently high, bound BH binaries can be
formed by the collision of their circum-single disks. Our analysis demonstrates
that, after a BH pair passes the pericenter of their relative trajectory, a gas
post-collision drag may slow down the BHs, possibly forcing the two BHs to stay
tightly bound. A binary formed by a close encounter can have a compact
semi-major axis, large eccentricity, and retrograde orbital angular momentum.
We provide a fitting formula that can accurately predict whether a close
encounter can form a binary based on the gas mass and the incoming energy of
the encounter. This fitting formula can be easily implemented in other
long-term simulations that study the dynamical evolution of BHs in AGN disks.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10357v1
