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Fact: Many SCUBA galaxies harbour AGNs

D. M. Alexander·F. E. Bauer·S. C. Chapman·I. Smail·A. W. Blain·W. N. Brandt·R. J. Ivison
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Abstract

Deep SCUBA surveys have uncovered a large population of ultra-luminous galaxies at z>1. These sources are often assumed to be starburst galaxies, but there is growing evidence that a substantial fraction host an AGN (i.e., an accreting super-massive black hole). We present here possibly the strongest evidence for this viewpoint to date: the combination of ultra-deep X-ray observations (the 2 Ms Chandra Deep Field-North) and deep optical spectroscopic data. We argue that upward of 38% of bright (f850um>=5mJy) SCUBA galaxies host an AGN, a fraction of which are obscured QSOs (i.e., L_X>3x10^{44} erg/s). However, using evidence from a variety of analyses, we argue that in almost all cases the AGNs are not bolometrically important (i.e., <20%). Thus, star formation appears to dominate their bolometric output. A substantial fraction of bright SCUBA galaxies show evidence for binary AGN activity. Since these systems appear to be interacting and merging at optical/near-IR wavelengths, their super-massive black holes will eventually coalesce.

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D. M. Alexander, F. E. Bauer, S. C. Chapman, I. Smail, A. W. Blain, W. N. Brandt, R. J. Ivison. 2004-01-08. Fact: Many SCUBA galaxies harbour AGNs. https://doi.org/10.1007/10995020_9

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