Active Galactic Nuclei Clustering in the Local Universe: An Unbiased Picture from Swift-BAT
Abstract
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 r 0 = 5.56+0.49 -0.43 Mpc h -1 and a slope γ = 1.64-0.08 -0.07. 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(M DMH)~ 12-14 h -1 M/M sun, depending on the subsample. For the whole sample, we measured log(M DMH)~ 13.15 h -1 M/M sun 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 M BH~(1-10) × 108 M sun and accreting with very low efficiency, log(epsilon)~-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 -1 M sun. We compared our results with clustering predictions of merger-driven AGN triggering models and found a good agreement.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2010
- DOI:
- 10.1088/2041-8205/716/2/L209
- arXiv:
- arXiv:1005.4968
- Bibcode:
- 2010ApJ...716L.209C
- Keywords:
-
- dark matter;
- diffuse radiation;
- galaxies: active;
- large-scale structure of universe;
- X-rays: galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 13 pages 3 figures, accepted by ApJ Letters