Active Galactic Nuclei Clustering in the Local Universe: An Unbiased Picture From Swift -Bat

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 ☉ , depending on the subsample. For the whole sample, we measured log( M DMH )∼ 13.15 h −1 M / M ☉ which is the typical mass of a galaxy group. We estimated that the local AGN population has a typical lifetime τ AGN ∼0.7 Gyr, it is powered by supermassive black hole with mass M BH ∼(1–10) × 10 8 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) × 10 10 h −1 M ☉ . We compared our results with clustering predictions of merger-driven AGN triggering models and found a good agreement.