Assigned ID: 768 ----- Attempting Submission 1 (Fri Mar 07 23:31:59 GMT 2008) ----- Our present understanding of galaxy evolution suggests that supermassive black holes (SMBH) commonly form binary systems in the cores of large galaxies. It is expected that the SMBH binary will ultimately undergo rapid coalescence in an enormous outburst of gravitational waves. Anisotropic emission of the gravitational radiation can impart a large recoil velocity to the merged SMBH, which may even exceed the escape velocity of the host galaxy. As SMBH are the engines of active galactic nuclei (AGN), the aftermath of SMBH coalescence may be observable as a displacement of the AGN from the centre of its host galaxy. Recent n-body simulations suggest that even if the SMBH fails to escape its host, it will undergo long-lived oscillations in the core of the galaxy after the initial large amplitude oscillations have been damped by dynamical friction. This implies that if binary coalescence is an important SMBH growth mechanism, the AGN should commonly be displaced from the center of the host galaxy. We therefore propose to search for such displacements using archival images of nearby Seyfert galaxies. Our aims are (1) to verify the displacements indicated by previous 2-D spectroscopy and spectroastrometric measurements. In doing so, will we explore and test a variety of techniques for accurately determining the center of the host galaxy bulge and quantify the associated uncertainties. (2) Measure AGN – galaxy center offsets in a larger sample of nearby Seyferts in order statistically quantify the occurrence of significant offsets and hence set limits on the frequency of possible binary SMBH mergers. (3) Search for relationships between displacement magnitude and direction and key properties of the AGN (including SBMH mass and radio source position angle) and host galaxy (e.g., hubble type, morphology evidence for past mergers). A null result would be equally important, since this would imply that binary SMBH do not occur in Seyfert hosts (mainly early-type spirals), or that they do not coalesce.

AGN/QUASARS 12 50000 false 0.0 0.0 false false false false false SUPPORTED