Title:  An Ultra-luminous Quasar with Most Massive Black Hole in the Distant Universe 

Speaker: Xue-Bing Wu (PKU/KIAA)   

Time & place: Thursday, 3:00pm, March 12th, lecture Hall, 3rd floor   

Abstract: To date about 40 quasars with redshifts z>6 have been discovered. Each quasar harbors a black hole with a mass of several billion solar masses. The existence of such black holes when the Universe was less than one billion years old presents significant challenges to theories of the formation and growth of black holes and the black hole/galaxy coev olution. I will report a recent discovery of an ultra-luminous quasar at redshift z=6.30, which has an observed optical and near-infrared luminosity a few times greater than those of previously known z>6 quasars. With near-infrared spectroscopy, we obtain a black hole mass of about 12 billion solar masses, which is well consistent with the mass derived by assuming an Eddington-limited accretion. This ultra-luminous quasar with a 12 billion solar mass black hole at z>6 provides a unique laboratory to the study of the mass assembly and galaxy formation around the most massive black holes in the early Universe.  

Biog: Xue-Bing Wu is a professor at Department of Astronomy, Peking University and the associate director of Kavli Institute for Astronomy and Astrophysics. He obtained his PhD from Beijing Astronomical Observatory (NAOC) in 1996. He then worked as a postdoc and visiting scholar at the Institute of Theoretical Physics of CAS, the University of Alabama in Huntsville, and the Max-Planck Institute for Astrophysics, before joining PKU in 2000. He was the deputy chair in 2003-2011 and chair in 2011-2014 of the Department of Astronomy at PKU. His main research interests include quasars and active galaxies, black hole accretion, high-energy astrophysics, and observational cosmology.