The mass function of active black holes in the local universe

Jenny E. Greene, Luis C. Ho

Research output: Contribution to journalArticlepeer-review

242 Scopus citations


We present the first measurement of the BH mass function for broad-line active galaxies in the local universe. Using the ∼8500 broad-line active galaxies from SDSS DR4, we construct a broad-line luminosity function that agrees very well with the local soft X-ray luminosity function. Using standard virial relations, we then convert observed broadline luminosities and widths into BH masses. A mass function constructed in this way has the unique capability to probe the mass region <106 M, which, while insignificant in terms of total BH mass density, nevertheless may place important constraints on the mass distribution of seed BHs in the early universe. The characteristic local active BH has a mass of ∼107 M radiating at 10% of the Eddington rate. The active fraction is a strong function of BH mass; at both higher and lower masses the active mass function falls more steeply than one would infer from the distribution of bulge luminosity. The deficit of local massive radiating BHs is a well-known phenomenon, while we present the first robust measurement of a decline in the space density of active BHs at low mass.

Original languageEnglish (US)
Pages (from-to)131-148
Number of pages18
JournalAstrophysical Journal
Issue number1 I
StatePublished - 2007

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: Seyfert
  • Galaxies: active
  • Galaxies: nuclei


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