An Observational Search for Supermassive Black Hole Binaries
Jessie Runnoe - University of Michigan
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 history of mergers and accretion over the course of cosmic time. 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 unambiguous observations of the close, bound binaries that are expected to follow have proven elusive. The detection of this population would contribute important evidence in favor of heirarchical galaxy evolution scenarios, 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). A sample of 88 binary candidates is therefore selected from z<0.7 Sloan Digital Sky Survey quasars via substantial (>1000 km/s) shifts of their broad H-beta lines relative to their systemic redshifts. I will present an update on my efforts to evaluate the credentials of the candidates via their multi-year spectroscopic variability properties and radial velocity curves.
Coffee and Donuts served in 4054 McPherson Lab at 2:00pm