THE QUEST FOR THE DYNAMICAL SIGNATURE OF CLOSE SUPERMASSIVE BINARY BLACK HOLES
THE QUEST FOR THE DYNAMICAL SIGNATURE OF CLOSE SUPERMASSIVE BINARY BLACK HOLES. Supermassive binary black holes (masses of order 1 million to 1 billion solar masses and separations less than 1 pc) are predicted to be an inevitable late stage in the evolution of galaxy mergers. Such binaries have also been invoked as explanations of the formation of the cores of elliptical galaxies following a merger and the mass deficits therein, the apparent precession of radio jets, and the formation of X-shaped radio sources and they are predicted to be prime sources of gravitational waves. Yet, they remain elusive. After a historical introduction, I will describe a systematic search for such objects using the SDSS spectroscopic database and the follow-up observations of the initial candidates. I will present the current results from this search and discuss critical tests of the methodology as well as plans for future work.