A Search for Inspiraling, Binary, and Recoiling Black Holes in Nearby Galaxies

Nearly all galaxy bulges contain supermassive black holes (SMBHs), so galaxy assembly by hierarchical merging should produce wide pairs of slowly inspiraling SMBHs that either stall as tight binaries with ~1 pc separation or merge and are kicked away from the galaxy nucleus by anisotropic gravitational radiation. We are making a systematic VLBA search for off- nuclear SMBHs and for tight SMBH pairs in a sample of 923 nearby (D~200 Mpc) 2MASS galaxies containing radio sources stronger than 100 mJy to study three scientific problems: (1) SMBH/galaxy co-evolution implied by the SMBH/bulge mass correlation, (2) the "merger tree" theory of SMBH evolution, and (3) the expected contribution of SMBH mergers to the gravitational-wave background. The VLBA at X band provides (1) the 1-2 mas resolution needed to distinguish radio cores near SMBHs from extended jets or compact starbursts and resolve tight SMBH binaries and (2) absolute SMBH positions with ~5 mas accuracy for comparison with 2MASS bulge positions having ~100 mas absolute accuracy, sufficient to detect SMBHs offset ~500 pc from their host nuclei.

James Condon, National Radio Astronomy Observatory
Jeremy Darling, University of Colorado at Boulder
Yuri Kovalev, Lebedev Physical Institute
Leonid Petrov, ADNET Systems Inc. / NASA Goddard Space Flight Center

For a detailed description of this project, see the .pdf presentation from the 2011 January 27–28 Workshop on the Future of the VLBA held in Charlottesville. The latest results from this project are available via the web site being maintained by Leonid Petrov. We have waived the proprietary period on our data.

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