Physics & Astronomy Colloquium

Speaker: Jessie Runnoe (University of Michigan)

Title: The ongoing hunt for supermassive black hole binaries

Abstract: Supermassive black hole binaries are thought to be an inevitable product of the prevailing galaxy evolution scenarios where most massive galaxies host a central black hole and undergo a long history of mergers and accretion. The early stages of this process have been observed in the form of interacting galaxy pairs as well as kilo-parsec separation dual active galactic nuclei, but the close, bound binaries that are expected to follow have proven elusive. The detection of this population would contribute important evidence in favor of hierarchical galaxy evolution, and is also of interest in other fields including gravitational wave astronomy. With this motivation, I have undertaken a systematic search for close supermassive black hole binaries based on the hypothesis that the secondary black hole in the system is active and the resulting broad emission lines will be doppler shifted due to its orbital motion (analogous to a single-line spectroscopic binary star). My sample of binary candidates is therefore selected from nearby quasars via substantial (>1000 km/s) shifts of the broad H-beta lines relative to the systemic redshift. I will present an update on the research program that I have been leading to evaluate the credentials of these candidates.

Speaker Biography: TBA