A systematic search for close supermassive black hole binaries in the Catalina Real-time Transient Survey
Abstract
Hierarchical assembly models predict a population of supermassive black hole (SMBH) binaries. These are not resolvable by direct imaging but may be detectable via periodic variability (or nanohertz frequency gravitational waves). Following our detection of a 5.2-year periodic signal in the quasar PG 1302−102, we present a novel analysis of the optical variability of 243 500 known spectroscopically confirmed quasars using data from the Catalina Real-time Transient Survey (CRTS) to look for close (<0.1 pc) SMBH systems. Looking for a strong Keplerian periodic signal with at least 1.5 cycles over a baseline of nine years, we find a sample of 111 candidate objects. This is in conservative agreement with theoretical predictions from models of binary SMBH populations. Simulated data sets, assuming stochastic variability, also produce no equivalent candidates implying a low likelihood of spurious detections. The periodicity seen is likely attributable to either jet precession, warped accretion discs or periodic accretion associated with a close SMBH binary system. We also consider how other SMBH binary candidates in the literature appear in CRTS data and show that none of these are equivalent to the identified objects. Finally, the distribution of objects found is consistent with that expected from a gravitational-wave-driven population. This implies that circumbinary gas is present at small orbital radii and is being perturbed by the black holes. None of the sources is expected to merge within at least the next century. This study opens a new unique window to study a population of close SMBH binaries that must exist according to our current understanding of galaxy and SMBH evolution.
Additional Information
© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 July 27. Received 2015 July 24; in original form 2015 June 9. First published online August 25, 2015. We thank the anonymous referee for their comments. We thank Zoltan Haiman, Chiara Mingarelli and Justin Ellis for useful discussions. This work was supported in part by the NSF grants AST-0909182, IIS-1118041 and AST-1313422, and by the W. M. Keck Institute for Space Studies. The work of DS was carried out at Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This work made use of the MQ catalogue. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III website is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington and Yale University.Attached Files
Published - MNRAS-2015-Graham-1562-76.pdf
Submitted - 1507.07603v1.pdf
Supplemental Material - supp-mat.zip
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Additional details
- Eprint ID
- 62261
- Resolver ID
- CaltechAUTHORS:20151119-140541834
- AST-0909182
- NSF
- IIS-1118041
- NSF
- AST-1313422
- NSF
- Keck Institute for Space Studies (KISS)
- NASA/JPL/Caltech
- Alfred P. Sloan Foundation
- Participating Institutions
- Department of Energy (DOE)
- Created
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2015-11-19Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field
- Caltech groups
- Keck Institute for Space Studies