Active galactic nuclei clustering in the local universe: An unbiased picture from swift-bat

N. Cappelluti, M. Ajello, D. Burlon, M. Krumpe, T. Miyaji, S. Bonoli, J. Greiner

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


We present the clustering measurement of hard X-ray selected active galactic nuclei (AGNs) in the local universe. We used a sample of 199 sources spectroscopically confirmed, detected by Swift-BAT in its 15-55 keV all-sky survey. We measured the real space projected autocorrelation function (ACF) and detected a signal significant on projected scales lower than 200 Mpc h-1. We measured a correlation length of r0 = 5.56-0.43+0.49 Mpc h-1 and a slope γ = 1.64-0.07-0.08. We also measured the ACF of Type I and Type II AGNs and found higher correlation length for Type I AGNs. We have a marginal evidence of luminosity dependent clustering of AGNs, as we detected a larger correlation length of luminous AGNs than that of low-luminosity sources. The corresponding typical host dark matter halo masses of Swift-BAT are ∼ log(MDMH)∼ 12-14 h-1M/M, depending on the subsample. For the whole sample, we measured log(MDMH)∼ 13.15 h-1M/M which is the typical mass of a galaxy group.We estimated that the local AGN population has a typical lifetime τAGN ∼0.7 Gyr, it is powered by supermassive black hole with mass MBH∼ (1-10) × 108 M and accreting with very low efficiency, log(∈)∼ -2.0. We also conclude that local AGN host galaxies are typically red-massive galaxies with stellar mass of the order (2-80) × 1010 h-1M.We compared our results with clustering predictions of merger-driven AGN triggering models and found a good agreement.

Original languageEnglish (US)
Pages (from-to)L209-L213
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Jun 20 2010
Externally publishedYes


  • Dark matter
  • Diffuse radiation
  • Galaxies: Active
  • Large-scale structure of universe
  • X-rays: Galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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