The luminosity function of X-ray-selected active galactic nuclei: Evolution of supermassive black holes at high redshift

J. D. Silverman, P. J. Green, W. A. Barkhouse, D. W. Kim, M. Kim, B. J. Wilkes, R. A. Cameron, G. Hasinger, B. T. Jannuzi, M. G. Smith, P. S. Smith, H. Tananbaum

Research output: Contribution to journalArticlepeer-review

230 Scopus citations


We present a measure of the hard (2-8 keV) X-ray luminosity function (XLF) of AGNs up to z ∼ 5. At high redshifts, the wide area coverage of the Chandra Multiwavength Project is crucial to detect rare and luminous (L X > 1044 ergs s-1) AGNs. The inclusion of samples from deeper published surveys, such as the Chandra Deep Fields, allows us to span the lower LX range of the XLF. Our sample is selected from both the hard (z < 3, f2-8 kev > 6.3 × 10-16 ergs cm-2 s-1) and soft (z > 3, f0.5-2.0kev > 1.0 × 10-16 ergs cm-2 s-1) energy band detections. Within our optical magnitude limits (r′, i′ < 24), we achieve an adequate level of completeness (>50%) regarding X-ray source identification (i.e., redshift). We find that the luminosity function is similar to that found in previous X-ray surveys up to z ∼ 3 with an evolution dependent on both luminosity and redshift. At z > 3, there is a significant decline in the numbers of AGNs with an evolution rate similar to that found by studies of optically selected QSOs. Based on our XLF, we assess the resolved fraction of the cosmic X-ray background, the cumulative mass density of SMBHs, and the comparison of the mean accretion rate onto SMBHs and the star formation history of galaxies as a function of redshift. A coevolution scenario up to z ∼ 2 is plausible, although at higher redshifts the accretion rate onto SMBHs drops more rapidly. Finally, we highlight the need for better statistics of high-redshift AGNs at z ≳ 3, which is achievable with the upcoming Chandra surveys.

Original languageEnglish (US)
Pages (from-to)118-139
Number of pages22
JournalAstrophysical Journal
Issue number1
StatePublished - May 20 2008


  • Galaxies: active
  • Quasars: general
  • Surveys
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'The luminosity function of X-ray-selected active galactic nuclei: Evolution of supermassive black holes at high redshift'. Together they form a unique fingerprint.

Cite this