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(-0.43)(+0.49) Mpc h(-1) and a slope gamma = 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 similar to log(M-DMH)similar to 12-14 h(-1)M/M-circle dot, depending on the subsample. For the whole sample, we measured log(M-DMH)similar to 13.15 h(-1)M/M-circle dot which is the typical mass of a galaxy group. We estimated that the local AGN population has a typical lifetime iota(AGN) similar to 0.7 Gyr, it is powered by supermassive black hole with mass M-BH similar to (1-10) x 10(8) M-circle dot and accreting with very low efficiency, log(epsilon)similar to -2.0. We also conclude that local AGN host galaxies are typically red-massive galaxies with stellar mass of the order (2-80) x 10(10) h(-1)M(circle dot). We compared our results with clustering predictions of merger-driven AGN triggering models and found a good agreement.