The existence of binary supermassive black holes (SBHs) is predicted by models of hierarchical galaxy formation. To date, only a single binary SBH has been imaged, at a projected separation of 7.3 pc. Here, we report the detection of a candidate dual SBH with projected separation of 0.35 pc in the gas-rich interacting spiral galaxy NGC 7674 (Mrk 533). This peculiar Seyfert galaxy possesses a roughly 0.7 kpc Z-shaped radio jet. The leading model for the formation of such sources postulates the presence of an uncoalesced binary SBH created during the infall of a satellite galaxy. Using very long baseline interferometry, we imaged the central region of Mrk 533 at radio frequencies of 2, 5, 8 and 15 GHz. Two, possibly inverted-spectrum, radio cores were detected at 15 GHz only. The 8–15 GHz spectral indices of the two cores were ≥−0.33 and ≥−0.38 (±30%), consistent with accreting SBHs. We derived a jet speed of around 0.28c from multi-epoch parsec-scale data of the hotspot region and a source age of ≥ 8.2 × 103 years.
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Sanders, D. B. & Mirabel, I. F. Luminous infrared galaxies. Annu. Rev. Astron. Astr. 34, 749–792 (1996).
Verdes-Montenegro, L. et al. Hickson 96: a physical compact group. Astron. Astrophys. 321, 409–423 (1997).
Lasker, B. M. et al. The Guide Star Catalog. I—Astronomical foundations and image processing. Astron. J. 99, 2019–2058 (1990).
Miller, J. S. & Goodrich, R. W. Spectropolarimetry of high-polarization Seyfert 2 galaxies and unified Seyfert theories. Astrophys. J. 355, 456–467 (1990).
Begelman, M. C., Blandford, R. D. & Rees, M. J. Massive black hole binaries in active galactic nuclei. Nature 287, 307–309 (1980).
Aguerri, J. A. L., Balcells, M. & Peletier, R. F. Growth of galactic bulges by mergers. I. Dense satellites. Astron. Astrophys. 367, 428–442 (2001).
Kormendy, J. & Ho, L. C. Coevolution (or not) of supermassive black holes and host galaxies. Annu. Rev. Astron. Astr. 51, 511–653 (2013).
Momjian, E., Romney, J. D., Carilli, C. L. & Troland, T. H. Sensitive VLBI continuum and H I absorption observations of NGC 7674: first scientific observations with the combined array VLBA, VLA, and Arecibo. Astrophys. J. 597, 809–822 (2003).
Barvainis, R., Lonsdale, C. & Antonucci, R. Radio spectra of radio quiet quasars. Astron. J. 111, 1431–1443 (1996).
Kharb, P. et al. Very Large Baseline Array observations of Mrk 6: probing the jet–lobe connection. Mon. Not. R. Astron. Soc. 440, 2976–2987 (2014).
Hancock, P. J., Sadler, E. M., Mahony, E. K. & Ricci, R. Observations and properties of candidate high-frequency GPS radio sources in the AT20G survey. Mon. Not. R. Astron. Soc. 408, 1187–1206 (2010).
Ulvestad, J. S., Antonucci, R. R. J. & Barvainis, R. VLBA imaging of central engines in radio-quiet quasars. Astrophys. J. 621, 123–129 (2005).
Varenius, E. et al. The population of SNe/SNRs in the starburst galaxy Arp 220. A self-consistent analysis of 20 years of VLBI monitoring. Preprint at https://arxiv.org/abs/1702.04772 (2017).
Pérez-Torres, M. A., Romero-Cañizales, C., Alberdi, A. & Polatidis, A. An extremely prolific supernova factory in the buried nucleus of the starburst galaxy IC 694. Astron. Astrophys. 507, L17–L20 (2009).
Rodriguez, C. et al. A compact supermassive binary black hole system. Astrophys. J. 646, 49–60 (2006).
Boroson, T. A. & Lauer, T. R. A candidate sub-parsec supermassive binary black hole system. Nature 458, 53–55 (2009).
Chornock, R. et al. SDSS J1536+0441: an extreme “double-peaked emitter,” not a binary black hole. The Astronomer’s Telegram 1955 (2009).
Wrobel, J. M. & Laor, A. Discovery of radio emission from the Quasar SDSS J1536+0441, a candidate binary black hole system. Astrophys. J. Lett. 699, L22–L25 (2009).
Woo, J.-H. & Urry, C. M. Active galactic nucleus black hole masses and bolometric luminosities. Astrophys. J. 579, 530–544 (2002).
Ferrarese, L. & Merritt, D. A fundamental relation between supermassive black holes and their host galaxies. Astrophys. J. Lett. 539, L9–L12 (2000).
Ho, L. C. Nuclear activity in nearby galaxies. Annu. Rev. Astron. Astr. 46, 475–539 (2008).
Hada, K. et al. An origin of the radio jet in M87 at the location of the central black hole. Nature 477, 185–187 (2011).
Peterson, B. M. & Cota, S. A. The size of the broad-line region in the Seyfert galaxy NGC 4151. Astrophys. J. 330, 111–120 (1988).
Pozo Nuñez, F. et al. The broad-line region and dust torus size of the Seyfert 1 galaxy PGC 50427. Astron. Astrophys. 576, A73 (2015).
Merritt, D. Dynamics and Evolution of Galactic Nuclei (Princeton Univ. Press, Princeton, NJ, 2013).
Lal, D. V., Shastri, P. & Gabuzda, D. C. Milliarcsec-scale radio structure of a matched sample of Seyfert 1 and Seyfert 2 galaxies. Astron. Astrophys. 425, 99–108 (2004).
Ulvestad, J. S. et al. Subrelativistic radio jets and parsec-scale absorption in two Seyfert galaxies. Astrophys. J. Lett. 517, L81–L84 (1999).
Bicknell, G. V., Dopita, M. A., Tsvetanov, Z. I. & Sutherland, R. S. Are Seyfert narrow-line regions powered by radio jets? Astrophys. J. 495, 680–690 (1998).
Middelberg, E. et al. Motion and properties of nuclear radio components in Seyfert galaxies seen with VLBI. Astron. Astrophys. 417, 925–944 (2004).
De Young, D. S. The Physics of Extragalactic Radio Sources (Univ. Chicago Press, Chicago, IL, 2002).
Gopal-Krishna, Biermann, P. L. & Wiita, P. J. The origin of X-shaped radio galaxies: clues from the Z-symmetric secondary lobes. Astrophys. J. Lett. 594, L103–L106 (2003).
Zier, C. Orientation and size of the ‘Z’ in X-shaped radio galaxies. Mon. Not. R. Astron. Soc. 364, 583–592 (2005).
Merritt, D. & Ekers, R. D. Tracing black hole mergers through radio lobe morphology. Science 297, 1310–1313 (2002).
Leahy, J. P. & Williams, A. G. The bridges of classical double radio sources. Mon. Not. R. Astron. Soc. 210, 929–951 (1984).
Worrall, D. M., Birkinshaw, M. & Cameron, R. A. The X-ray environment of the dumbbell radio galaxy NGC 326. Astrophys. J. 449, 93–104 (1995).
Milosavljević, M. & Merritt, D. in The Astrophysics of Gravitational Wave Sources (ed. Centrella, J. M.) 201–210 (2003).
Bardeen, J. M. & Petterson, J. A. The Lense–Thirring effect and accretion disks around Kerr black holes. Astrophys. J. Lett. 195, L65–L67 (1975).
Valtonen, M. J. New orbit solutions for the precessing binary black hole model of OJ 287. Astrophys. J. 659, 1074–1081 (2007).
Graham, M. J. et al. A possible close supermassive black-hole binary in a quasar with optical periodicity. Nature 518, 74–76 (2015).
Cordes, J. M. Limits to PTA sensitivity: spin stability and arrival time precision of millisecond pulsars. Class. Quantum Grav. 30, 224002 (2013).
Huerta, E. A., McWilliams, S. T., Gair, J. R. & Taylor, S. R. Detection of eccentric supermassive black hole binaries with pulsar timing arrays: signal-to-noise ratio calculations. Phys. Rev. D 92, 063010 (2015).
Babak, S. et al. European pulsar timing array limits on continuous gravitational waves from individual supermassive black hole binaries. Mon. Not. R. Astron. Soc. 455, 1665–1679 (2016).
Rasskazov, A. & Merritt, D. Evolution of massive black hole binaries in rotating stellar nuclei: Implications for gravitational wave detection. Preprint at https://arxiv.org/abs/1606.07484 (2016).
Amaro Seoane, P. et al. The Gravitational Universe. Preprint at https://arxiv.org/abs/1305.5720 (2013).
P.K. and D.V.L. thank D. C. Gabuzda for help in obtaining the 1998 and 2002 VLBA data and provision of expert knowledge on VLBI data reduction. D.M. was supported by the National Science Foundation under grant no. AST 1211602 and the National Aeronautics and Space Administration under grant no. NNX13AG92G. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities.
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Kharb, P., Lal, D.V. & Merritt, D. A candidate sub-parsec binary black hole in the Seyfert galaxy NGC 7674. Nat Astron 1, 727–733 (2017). https://doi.org/10.1038/s41550-017-0256-4