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Unveiling the population of dual and lensed active galactic nuclei at sub-arcsec separations

Nature Astronomy volume 6, pages 1185–1192 (2022)Cite this article

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Abstract

All cosmological models of structure formation predict the existence of a widespread population of dual supermassive black holes in-spiralling inside their common host galaxy, eventually merging and giving rise to intense gravitational waves. These systems can be identified as dual active galactic nuclei (AGNs) at kiloparsec separations, but only very few have been confirmed at z > 0.5. The appearance of multiple AGNs at small angular separations can also be due to gravitational lensing of single AGNs, which are themselves very important systems for many astrophysical topics. Here we present a novel technique, dubbed the Gaia multipeak method, to obtain large and reliable samples of dual/lensed AGN candidates with sub-arcsec separations by looking for AGNs showing multiple peaks in the light profiles observed by the Gaia satellite. All of the Gaia multipeak method-selected sources with high-resolution images (26 from the Hubble Space Telescope archive and 5 from dedicated adaptive-optics-assisted imaging at the Large Binocular Telescope) show multiple components with sub-arcsec separation pointing toward a very high reliability of the method. By sampling separations down to ~2 kpc at z > 1, this method allows us to probe the physical processes that drive the in-spiralling of a pair of supermassive black holes inside a single galaxy.

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Fig. 1: Archival HST images of the GMP-selected dual/lensed AGN candidates.
Fig. 2: High-resolution, AO-assisted LBT images of 5 GMP-selected systems in the Ks band.
Fig. 3: HST/STIS spectrum of the binary system J0841+4825 at z = 2.95.
Fig. 4: Optical colours of the primary and secondary components of the spectroscopically confirmed dual AGN J0841+4825 and of the nine unclassified systems observed by HST.

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Data availability

The Gaia catalogue is publicly available at https://gea.esac.esa.int/archive/. The HST data are publicly available via the Mikulski Archive for Space Telescopes at https://archive.stsci.edu. The Milliquas catalogue of the parent AGNs is available at https://heasarc.gsfc.nasa.gov/W3Browse/all/milliquas.html. SDSS spectra can be downloaded from https://www.sdss.org/dr16.

References

  1. Colpi, M. Massive binary black holes in galactic nuclei and their path to coalescence. Space Sci. Rev. 183, 189 (2014).

    Article  ADS  Google Scholar 

  2. Volonteri, M., Habouzit, M. & Colpi, M. The origins of massive black holes. Nat. Rev. Phys. 3, 732 (2021).

    Article  Google Scholar 

  3. Koss, M. J. et al. A population of luminous accreting black holes with hidden mergers. Nature 563, 214 (2018).

    Article  ADS  Google Scholar 

  4. Liu, X. et al. Hubble Space Telescope Wide Field Camera 3 identifies an r = 1 Kpc dual active galactic nucleus in the minor galaxy merger SDSS J0924+0510 at z = 0.1495. Astrophys. J. 862, 29 (2018).

    Article  ADS  Google Scholar 

  5. Severgnini, P. et al. A possible sub-kiloparsec dual AGN buried behind the galaxy curtain. Astron. Astrophys. 646, A153 (2021).

    Article  Google Scholar 

  6. De Rosa, A. et al. The quest for dual and binary supermassive black holes: a multi-messenger view. N. Astron. Rev. 86, 101525 (2019).

    Article  Google Scholar 

  7. Silverman, J. D. et al. Dual supermassive black holes at close separation revealed by the Hyper Suprime-Cam Subaru Strategic Program. Astrophys. J. 899, 154 (2020).

    Article  ADS  Google Scholar 

  8. Chen, Y.-C. Small-scale double quasars discovered in the DECam Legacy Survey. Preprint at https://arxiv.org/abs/2109.06881 (2021).

  9. Schechter, P. L. et al. First lensed quasar systems from the VST-ATLAS Survey: one quad, two doubles, and two pairs of lensless twins. Astron. J. 153, 219 (2017).

    Article  ADS  Google Scholar 

  10. Anguita, T. et al. The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 follow-up campaign - II. New quasar lenses from double component fitting. Mon. Not. R. Astron. Soc. 480, 5017 (2018).

    ADS  Google Scholar 

  11. Lemon, C. et al. J1721+8842: a gravitationally lensed binary quasar with a proximate damped Lyman-α absorber. Astron. Astrophys. 657, 113 (2022).

    Article  Google Scholar 

  12. Amante, M. H. et al. Testing dark energy models with a new sample of strong-lensing systems. Mon. Not. R. Astron. Soc. 498, 6013 (2020).

    Article  ADS  Google Scholar 

  13. Wong, K. C. et al. H0LiCOW—XIII. A 2.4 per cent measurement of H0 from lensed quasars: 5.3σ tension between early- and late-Universe probes. Mon. Not. R. Astron. Soc. 498, 1420 (2020).

    Article  ADS  Google Scholar 

  14. Feruglio, C. et al. On the discovery of fast molecular gas in the UFO/BAL quasar APM 08279+5255 at z = 3.912. Astron. Astrophys. 608, A30 (2017).

    Article  Google Scholar 

  15. Tozzi, G. et al. Connecting X-ray nuclear winds with galaxy-scale ionised outflows in two z ∼ 1.5 lensed quasars. Astron. Astrophys. 648, A99 (2021).

    Article  Google Scholar 

  16. Shen, Y. et al. A hidden population of high-redshift double quasars unveiled by astrometry. Nat. Astron 5, 569–574 (2021).

    Article  ADS  Google Scholar 

  17. Junkkarinen, V. et al. LBQS 0103-2753: a 0.3″ binary quasar. Astrophys. J. 549, L155 (2001).

    Article  ADS  Google Scholar 

  18. Rowell, N. et al. Gaia Early Data Release 3. Modelling and calibration of Gaia's point and line spread functions. Astron. Astrophys. 649, A11 (2021).

    Article  Google Scholar 

  19. Hambly, N. C. et al. Gaia Data Release 2. Calibration and mitigation of electronic offset effects in the data. Astron. Astrophys. 616, A15 (2018).

    Article  Google Scholar 

  20. Gaia Collaboration, Brown. et al. Gaia Early Data Release 3. Summary of the contents and survey properties. Astron. Astrophys. 649, A1 (2021).

    Article  Google Scholar 

  21. Riello, M. et al. Gaia Early Data Release 3. Photometric content and validation. Astron. Astrophys. 649, A3 (2021).

    Article  Google Scholar 

  22. Lindegren, L. et al. Gaia Early Data Release 3. The astrometric solution. Astron. Astrophys. 649, A2 (2021).

    Article  Google Scholar 

  23. Fabricius, C. et al. Gaia Early Data Release 3. Catalogue validation. Astron. Astrophys. 649, A5 (2021).

    Article  Google Scholar 

  24. Chen, Y.-C. et al. Varstrometry for off-nucleus and dual sub-kpc AGN (VODKA): Hubble Space Telescope discovers double quasars. Astrophys. J. 925, 162C (2022).

    Article  ADS  Google Scholar 

  25. Lieu, R. Strong-lensing time delay: a new way of measuring cosmic shear. Astrophys. J. 674, 75 (2008).

    Article  ADS  Google Scholar 

  26. Grier, C. J. et al. The Sloan Digital Sky Survey reverberation mapping project: Hα and Hβ reverberation measurements from first-year spectroscopy and photometry. Astrophys. J. 851, 21 (2017).

    Article  ADS  Google Scholar 

  27. Kaspi, S. et al. Taking a long look: a two-decade reverberation mapping study of high-luminosity quasars. Astrophys. J. 915, 129 (2021).

    Article  ADS  Google Scholar 

  28. Girardi, L. et al. Theoretical isochrones in several photometric systems. I. Johnson–Cousins–Glass, HST/WFPC2, HST/NICMOS, Washington, and ESO Imaging Survey filter sets. Astron. Astrophys. 391, 195 (2002).

    Article  ADS  Google Scholar 

  29. Lyke, B. W. et al. The Sloan Digital Sky Survey quasar catalog: sixteenth data release. Astrophys. J. Suppl. Ser. 250, 8 (2020).

    Article  ADS  Google Scholar 

  30. Maraston, C. et al. Stellar population models based on the SDSS-IV MaStar library of stellar spectra—I. Intermediate-age/old models. Mon. Not. R. Astron. Soc. 496, 2962 (2020).

    Article  ADS  Google Scholar 

  31. Li, K., Ballantyne, D. R. & Bogdanović, T. The detectability of kiloparsec-scale dual active galactic nuclei: the impact of galactic structure and black hole orbital properties. Astrophys. J. 916, 110 (2021).

    Article  ADS  Google Scholar 

  32. Steinborn, L. K. et al. Origin and properties of dual and offset active galactic nuclei in a cosmological simulation at z = 2. Mon. Not. R. Astron. Soc. 458, 1013 (2016).

    Article  ADS  Google Scholar 

  33. Eftekharzadeh, S. et al. Clustering of intermediate redshift quasars using the final SDSS III-BOSS sample. Mon. Not. R. Astron. Soc. 453, 2779 (2015).

    Article  ADS  Google Scholar 

  34. Rosas-Guevara, Y. M. et al. The abundances and properties of dual AGN and their host galaxies in the EAGLE simulations. Mon. Not. R. Astron. Soc. 483, 2712 (2019).

    Article  ADS  Google Scholar 

  35. Comerford, J. M. et al. Inspiralling supermassive black holes: a new signpost for galaxy mergers. Astrophys. J. 698, 956 (2009).

    Article  ADS  Google Scholar 

  36. Volonteri, M. et al. The cosmic evolution of massive black holes in the Horizon-AGN simulation. Mon. Not. R. Astron. Soc. 460, 2979 (2016).

    Article  ADS  Google Scholar 

  37. Van Wassenhove, S. et al. Observability of dual active galactic nuclei in merging galaxies. Astrophys. J. 748, L7 (2012).

    Article  ADS  Google Scholar 

  38. Capelo, P. R. et al. A survey of dual active galactic nuclei in simulations of galaxy mergers: frequency and properties. Mon. Not. R. Astron. Soc. 469, 4437 (2017).

    Article  ADS  Google Scholar 

  39. Blecha, L. et al. The power of infrared AGN selection in mergers: a theoretical study. Mon. Not. R. Astron. Soc. 478, 3056 (2018).

    Article  ADS  Google Scholar 

  40. Biava, N. et al. The lifetime of binary black holes in Sérsic galaxy models. Mon. Not. R. Astron. Soc. 487, 4985 (2019).

    Article  ADS  Google Scholar 

  41. Begelman, M. C., Blandford, R. D. & Rees, M. J. Massive black hole binaries in active galactic nuclei. Nature 287, 307 (1980).

    Article  ADS  Google Scholar 

  42. Yu, Q. Evolution of massive binary black holes. Mon. Not. R. Astron. Soc. 331, 935 (2002).

    Article  ADS  Google Scholar 

  43. Tamfal, T. et al. Formation of LISA black hole binaries in merging dwarf galaxies: the imprint of dark matter. Astrophys. J. 864, L19 (2018).

    Article  ADS  Google Scholar 

  44. Tamburello, V. et al. Supermassive black hole pairs in clumpy galaxies at high redshift: delayed binary formation and concurrent mass growth. Mon. Not. R. Astron. Soc. 464, 2952 (2017).

    Article  ADS  Google Scholar 

  45. Rauch, M. et al. Small-scale structure at high redshift. III. The clumpiness of the intergalactic medium on subkiloparsec scales. Astrophys. J. 562, 76 (2001).

    Article  ADS  Google Scholar 

  46. Tejos, N. et al. Telltale signs of metal recycling in the circumgalactic medium of a z 0.77 galaxy. Mon. Not. R. Astron. Soc. 507, 663 (2021).

    Article  ADS  Google Scholar 

  47. Mortensen, K. et al. Kinematics of the circumgalactic medium of a z = 0.77 galaxy from Mg ii tomography. Astrophys. J. 914, 92 (2021).

    Article  ADS  Google Scholar 

  48. Peng, C. Y. et al. Probing the coevolution of supermassive black holes and galaxies using gravitationally lensed quasar hosts. Astrophys. J. 649, 616 (2006).

    Article  ADS  Google Scholar 

  49. Casadio, C. et al. SMILE: Search for MIlli-LEnses. Mon. Not. R. Astron. Soc. 507, L6 (2021).

    Article  ADS  Google Scholar 

  50. Kochaneck, C. in Gravitational Lensing: Strong, Weak and Micro. Saas-Fee Advanced Course 33 (eds Meylan, G. et al.) 91-268 (Springer, 2006).

  51. Gaia Collaboration, Prusti. et al. The Gaia mission. Astron. Astrophys. 595, A1 (2016).

    Article  Google Scholar 

  52. Pancino, E. et al. Globular clusters with Gaia. Mon. Not. R. Astron. Soc. 467, 412 (2017).

    ADS  Google Scholar 

  53. Flesch, E. W. The Million Quasars (Milliquas) v7.2 Catalogue, now with VLASS associations. The inclusion of SDSS-DR16Q quasars is detailed. Preprint at https://arxiv.org/abs/2105.12985 (2021).

  54. Mandel, H. et al. LUCIFER: a NIR spectrograph and imager for the LBT. Astron. Nachr. 328, 626 (2007).

    ADS  Google Scholar 

  55. Pinna, E. et al. SOUL: the single conjugated adaptive optics upgrade for LBT adaptive optics systems. Proc. SPIE Int. Soc. Opt. Eng. 9909, 99093V (2016).

    Google Scholar 

  56. Pinna, E. et al. Bringing SOUL on sky. Preprint at https://arxiv.org/abs/2101.07091 (2021).

  57. Hwang, H.-C. et al. Varstrometry for off-nucleus and dual subkiloparsec AGN (VODKA): methodology and initial results with Gaia DR2. Astrophys. J. 888, 73 (2020).

    Article  ADS  Google Scholar 

  58. Calzetti, D. et al. The dust content and opacity of actively star-forming galaxies. Astrophys. J. 533, 682 (2000).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. Funding for the SDSS has been provided by the Alfred P. Sloan Foundation, the US Department of Energy Office of Science and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. We are grateful to all the LBT staff that performed the requested observations. The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, representing OSU, University of Notre Dame, University of Minnesota and University of Virginia.

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Authors and Affiliations

  1. INAF—Osservatorio Astrofisico di Arcetri, Florence, Italy

    F. Mannucci, E. Pancino, F. Belfiore, G. Cresci, E. Lusso, A. Marasco, A. Marconi, E. Nardini, E. Pinna & G. Tozzi

  2. Space Science Data Center—ASI, Rome, Italy

    E. Pancino

  3. Institute of Theoretical Astrophysics, University of Oslo, Oslo, Norway

    C. Cicone

  4. Univ. of California Los Angeles, Los Angeles, CA, USA

    A. Ciurlo

  5. Dip. di Fisica e Astronomia, Univ. di Firenze, Florence, Italy

    E. Lusso, A. Marconi & G. Tozzi

  6. INAF—Osservatorio Astronomico di Brera, Milan, Italy

    P. Severgnini & P. Saracco

  7. Cavendish Laboratory, University of Cambridge, Cambridge, UK

    G. Tozzi

  8. W. M. Keck Observatory, Kamuela, HI, USA

    S. Yeh

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Contributions

F.M. designed and coordinated the work, prepared the figures and drafted the manuscript. E. Pancino provided the knowledge of the Gaia database parameters. All authors have contributed to the analysis and interpretation of the data and to the final text.

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Correspondence to F. Mannucci.

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Extended data

Extended Data Fig. 1 Separation sensitivity of the GMP method.

Estimated fraction of pairs that are not split in the Gaia EDR3 catalogue as a function of separation. To consider pairs similar to the dual AGNs, we limit the luminosity of the primary and secondary objects to 17 < G < 20 and 17 < G < 21, respectively. The dotted line shows an analytic fit to the curve. Right: Values of ipd_frac_multi_peak for the primary component of split pairs for the same magnitude ranges as in the left panel. The solid line shows median values as a function of separation, while the shaded regions show the 25%–75% and 10%−90% distributions. The blue horizontal dashed line shows the threshold used for this work.

Extended Data Fig. 2 Distribution of ipd_frac_multi_peak of the 221 candidates of the primary sample vs. redshift, colour-coded with their G-band magnitude.

For clarity, values of the ipd_frac_multi_peak larger than 40% are plotted at this value. The grayscale image shows the distribution of the input catalogue of AGN, strongly peaked at very low values of ipd_frac_multi_peak. The black diamonds identify the objects with archival HST images.

Extended Data Fig. 3 Values of the ipd_frac_multi_peak (presence of multiple peaks) as a function of RUWE (normalised extra astrometric jitter) for the 221 systems of the primary sample, colour-coded with their G-band magnitude.

For clarity, objects with values of RUWE larger than 3.5 and of ipd_frac_multi_peak larger than 40% are plotted at these values, respectively. The grayscale image shows the distribution of the input catalogue of AGN, peaked at low values of ipd_frac_multi_peak but spanning a significant range of RUWE. The dotted line shows the threshold RUWE = 1.4. The black diamonds identify the objects with archival HST images.

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Mannucci, F., Pancino, E., Belfiore, F. et al. Unveiling the population of dual and lensed active galactic nuclei at sub-arcsec separations. Nat Astron 6, 1185–1192 (2022). https://doi.org/10.1038/s41550-022-01761-5

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