Observational limits on type 1 active galactic nucleus accretion rate in COSMOS

Jonathan R. Trump, Chris D. Impey, Brandon C. Kelly, Martin Elvis, Andrea Merloni, Angela Bongiorno, Jared Gabor, Heng Hao, Patrick J. McCarthy, John P. Huchra, Marcella Brusa, Nico Cappelluti, Anton Koekemoer, Tohru Nagao, Mara Salvato, Nick Z. Scoville

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


We present black hole masses and accretion rates for 182 Type 1 active galactic nuclei (AGNs) in COSMOS. We estimate masses using the scaling relations for the broad H β, Mg ii, and C iv emission lines in the redshift ranges 0.16 < z < 0.88, 1 < z < 2.4, and 2.7 < z < 4.9. We estimate the accretion rate using an Eddington ratio LI/LEdd estimated from optical and X-ray data. We find that very few Type 1 AGNs accrete below LI/LEdd ∼ 0.01, despite simulations of synthetic spectra which show that the survey is sensitive to such Type 1 AGNs. At lower accretion rates the broad-line region may become obscured, diluted, or nonexistent. We find evidence that Type 1 AGNs at higher accretion rates have higher optical luminosities, as more of their emission comes from the cool (optical) accretion disk with respect to shorter wavelengths. We measure a larger range in accretion rate than previous works, suggesting that COSMOS is more efficient at finding low accretion rate Type 1 AGNs. However, the measured range in accretion rate is still comparable to the intrinsic scatter from the scaling relations, suggesting that Type 1 AGNs accrete at a narrow range of Eddington ratio, with LI/LEdd ∼ 0.1.

Original languageEnglish (US)
Pages (from-to)49-55
Number of pages7
JournalAstrophysical Journal
Issue number1
StatePublished - Jul 20 2009


  • Galaxies: active
  • Quasars: emission lines
  • Quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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