Title: A tale of two black holes: where are kpc-scale binary active galactic nuclei?
Speaker: Dr. Xin Liu (Einstein Fellow )
Affiliation: Harvard-Smithsonian Center for Astrophysics (CfA) of the United States
Time: Aug, 18th, 2pm
Location: Middle conference room, 3rd floor
Abstract: Despite decades of searching, and strong theoretical reasons to believe they exist, merging supermassive black holes (SMBHs) remain difficult to find. We have developed a feasible and effective strategy to systematically identify kpc-scale binary active SMBHs in optically selected AGNs from the SDSS that show double-peaked [O III] 4959,5007 emission lines. Using high resolution NIR imaging and spatially resolved optical spectroscopy, our pilot program with the Magellan and APO 3.5 m telescopes has uncovered four kpc-scale binary AGNs from 43 double-peaked objects. Meanwhile, we find that the majority of AGNs with double-peaked narrow emission lines are likely due to peculiar gas kinematics around a single SMBH. Neither high resolution imaging nor spatially resolved [O III] emission alone is sufficient to pin down their nature. A statistical sample of kpc-scale binary AGNs, once gathered,will provide invaluable constraints on the hierarchical paradigm of galaxy formation. It may also offer crucial insights into how merger-induced AGN activity affects galaxy growth and help make realistic forcast for the abundance of low-frequency gravitational wave sources detectable with the future eLISA and PTA.
