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Supermassive black hole (SMBH) binaries, formed during galaxy mergers, are the primary targets for low-frequency gravitational wave (GW) observatories. Understanding the coalescence process of SMBH binaries in a cosmological galaxy formation context is crucial for accurate GW predictions. However, this has been a long-standing challenge: traditional galaxy formation simulations lack the force resolution to follow SMBH dynamics, instead resorting to artificial repositioning and instantaneous mergers at kpc-scale separations. This limitation introduces significant uncertainty into estimates of SMBH coalescence timescales. In this talk, I will discuss the KETJU code, a newly developed numerical tool capable of simultaneously following galaxy (hydro-)dynamics and resolving SMBH dynamics with post-Newtonian corrections down to a few tens of Schwarzschild radii. This numerical tool enables us to improve the estimation of the SMBH merger time-scales, especially in gas-rich galaxy mergers, and study the impact of SMBH binaries on their host galaxies.
BIO

Dr. Shihong Liao obtained his PhD from the Chinese University of Hong Kong and subsequently conducted postdoctoral research at the National Astronomical Observatories, CAS (NAOC) and the University of Helsinki. He is currently a researcher at NAOC. His research focuses on galaxy formation, supermassive black holes, and cosmological simulations.

Host: Yi Mao