The Dynamics & Multi-messenger Signatures of Supermassive Black Hole Evolution

Supermassive black holes (SMBHs), with masses millions to billions times the mass of the Sun, are of great interest both as critical components in galaxy evolution and as the dominant sources of low-frequency gravitational waves (GWs). I will describe our recent results illustrating the role of galaxy mergers in SMBH fueling; in particular, nuclear obscuration during galaxy mergers likely plays a significant role in the elusive nature of BH pairs, and our work demonstrates that a high fraction of infrared-selected merging galaxies should contain BH pairs resolvable with JWST or with future X-ray imaging. I will also discuss current plans to construct new state-of-the-art models of the impact of SMBH feedback on galaxies. In addition, we have made recent progress in constraining the dynamics and multi-messenger signatures of BH pairs, binaries, and GW recoils, utilizing results from galactic- to cosmological-scale hydrodynamics simulations coupled with SMBH binary inspiral and spin evolution models.

Electromagnetic detections of such systems in the coming years will be crucial counterparts for the likely imminent detection of GWs by pulsar timing arrays, and they will provide key constraints on LISA event rates. I will conclude by describing ongoing work to constrain the formation of SMBH “seeds” in the early Universe, and the impact of various formation channels on the LISA source population.