CRA Seminar: Jiaru Li (Cornell)

Title: Formation of Black Hole Binaries in AGN disks through Close Encounters

Abstract: The possibility of binary black hole (BH) mergers in active galactic nucleus (AGN) accretion disks has recently received much attention. The community has studied the evolution of pre-existing BH binaries in AGN disks. However, how to form these BH binaries initially remains an open question. In this talk, I will show that close encounters between single BHs may produce these BH binaries in AGN disks. I will start with an N-body study. We explore the characteristics of the close encounters in an AGN disk and calculate the rate of binary formation due to gravitational-wave capture. Then I will present our 2D hydrodynamics simulations where BH close encounters happen in a live gaseous disk. We describe a departure-drag mechanism that can produce long-lived binaries, assess the probability of gas-assist formation of binaries, and characterize the properties of the resulting BH binary orbits.

Bio: Jiaru Li is an astronomy Ph.D. student at Cornell University, advised by Prof. Dong Lai. He also spent two years of grad school at Los Alamos National Laboratory as a CSES student fellow, where he worked with the group led by Dr. Hui Li. Jiaru Li received his bachelor’s degree at the University of Toronto, where he worked with Prof. Artur Izmaylov on quantum chemistry. His current research interests include exoplanet dynamics, protoplanetary disks, and the dynamical evolution of objects embedded in disks.