Title: Supermassive binary black holes in galactic centers: theoretical and observational perspectives

Speaker: Youjun Lu (NAOC)

Time & Place: Thursday, 3:00pm, April 24th, Lecture Hall, 3rd floor  

Abstract: The study of supermassive binary black holes (BBHs) is of great importance for various topics in physics and astrophysics, including detection of gravitational waves and cosmic evolution of galaxies and supermassive black holes (SMBHs). Formation of BBHs in galactic centres is an inevitable consequence of hierarchical mergers of galaxies in the standard LambdaCDM cosmology and BBHs may be abundant. However, direct observational evidence for the existence of BBHs remains elusive. I will review the orbital evolution of BBHs and the characteristic observational features of BBHs at different evolutionary stages and how these features can be used to identify BBHs, focusing on a few probes that we proposed. I will also summarise previous and ongoing efforts in searching BBHs and discuss how the current observations, specifically on the frequency of dual AGNs, can be used to constrain the evolution of BBHs and the triggering mechanism of nuclear activities. 

Biog: Youjun Lu is a professor at National Astronomical Observatories of China. He obtained his Ph.D. in Astrophysics from University of Science and Technology of China (USTC) in 1997. His research interests include black hole physics, active galactic nuclei and QSOs, galactic dynamics, galaxy formation and evolution, and cosmology.