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WEIGHING THE BLACK HOLES IN Z ≈ 2 SUBMILLIMETER-EMITTING GALAXIES HOSTING ACTIVE GALACTIC NUCLEI

By D. M. Alexander, W. N. Brandt, I. Smail, A. M. Swinbank, F. E. Bauer, A. W. Blain, S. C. Chapman, K. E. K. Coppin, R. J. Ivison and K. Menéndez-delmestre

Abstract

We place direct observational constraints on the black-hole masses (MBH) of the cosmologically important z ≈ 2 submillimeter-emitting galaxy (SMG; f850µm> ∼ 4 mJy) population, and use measured host-galaxy masses to explore their evolutionary status. We employ the well-established virial black-hole mass estimator to “weigh ” the black holes of a sample of z ≈ 2 SMGs which exhibit broad Hα or Hβ emission. We find that the average black-hole mass and Eddington ratio (η = Lbol/LEdd) of the lower-luminosity broad-line SMGs (LX ≈ 1044 erg s−1) are log(MBH/M⊙) ≈ 8.0 and η ≈ 0.2, respectively; by comparison, X-ray luminous broadline SMGs (LX ≈ 1045 erg s−1) have log(MBH/M⊙) ≈ 8.4 and η ≈ 0.6. The lower-luminosity broad-line SMGs lie in the same location of the LX–LFIR plane as more typical SMGs hosting X-ray obscured active galactic nuclei and may be intrinsically similar systems, but orientated so that the rest-frame optical nucleus is visible. Under this hypothesis, we conclude that SMGs host black holes with log(MBH/M⊙) ≈ 7.8; we find supporting evidence from observations of local ultra-luminous infrared galaxies. Combining these black-hole mass constraints with measured host-galaxy masses, we find that the black holes in SMGs are> ∼ 3 times smaller tha

Year: 2008
OAI identifier: oai:CiteSeerX.psu:10.1.1.314.1583
Provided by: CiteSeerX
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