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Binary Active Galactic Nuclei in Stripe 82: Constraints on Synchronized Black Hole Accretion in Major Mergers

Fu, Hai and Wrobel, J. M. and Myers, A. D. and Djorgovski, S. G. and Yan, Lin (2015) Binary Active Galactic Nuclei in Stripe 82: Constraints on Synchronized Black Hole Accretion in Major Mergers. Astrophysical Journal Letters, 815 (1). Art. No. L6. ISSN 2041-8205.

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Representing simultaneous black hole accretion during a merger, binary active galactic nuclei (AGNs) could provide valuable observational constraints to models of galaxy mergers and AGN triggering. High-resolution radio interferometer imaging offers a promising method for identifying a large and uniform sample of binary AGNs because it probes a generic feature of nuclear activity and is free from dust obscuration. Our previous search yielded 52 strong candidates of kiloparsec-scale binaries over the 92 deg^2 of the Sloan Digital Sky Survey Stripe 82 area with 2"-resolution Very Large Array (VLA) images. Here we present 0."3-resolution VLA 6 GHz observations for six candidates that have complete optical spectroscopy. The new data confirm the binary nature of four candidates and identify the other two as line of sight projections of radio structures from single AGNs. The four binary AGNs at z ~ 0.1 reside in major mergers with projected separations of 4.2–12 kpc. Optical spectral modeling shows that their hosts have stellar masses between 10.3 <log(M_*/M_☉)< 11.5 and velocity dispersions between 120<σ_*< 320 km s^(−1). The radio emission is compact (lesssim0farcs4) and shows a steep spectrum -1.8\< ɑ < -0.5) at 6 GHz. The host galaxy properties and the Eddington-scaled accretion rates broadly correlate with the excitation state, similar to the general radio-AGN population at low redshifts. Our estimated binary AGN fraction indicates that simultaneous accretion occurs ⩾23_(-8)^(+15) of the time when a kiloparsec-scale galaxy pair is detectable as a radio-AGN. The high duty cycle of the binary phase strongly suggests that major mergers can trigger and synchronize black hole accretion.

Item Type:Article
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URLURL TypeDescription Paper
Fu, Hai0000-0001-9608-6395
Wrobel, J. M.0000-0001-9720-7398
Djorgovski, S. G.0000-0002-0603-3087
Yan, Lin0000-0003-1710-9339
Additional Information:© 2015 The American Astronomical Society. Received 2015 September 30; accepted 2015 November 19; published 2015 December 3. We thank Cornelia Liang, Robert Mutel, Steve Spangler, and Alan Stockton for helpful discussions and the referee for useful comments. H.F. was partially supported by NASA JPL award 1495624 and University of Iowa funds. A.D.M. was partially supported by NASA ADAP award NNX12AE38G and by NSF awards 1211112 and 1515404. S.G.D. acknowledges support from NSF award AST-1413600. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. Facilities: VLA, Sloan, UKIRT, Keck:I.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
University of IowaUNSPECIFIED
Subject Keywords:galaxies: active; galaxies: interactions; galaxies: nuclei; galaxies: Seyfert
Issue or Number:1
Record Number:CaltechAUTHORS:20160111-085514577
Persistent URL:
Official Citation:Hai Fu et al 2015 ApJ 815 L6
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63531
Deposited By: Ruth Sustaita
Deposited On:12 Jan 2016 23:44
Last Modified:09 Mar 2020 13:19

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