The Asiago-ESO/RASS QSO Survey. III. Clustering Analysis and Theoretical Interpretation

This is the third paper in a series describing the Asiago-ESO/RASS QSO Survey (AERQS), a project aimed at the construction of an all-sky statistically well-defined sample of relatively bright quasi-stellar objects (QSOs; B<=15) at z<=0.3. We present here the clustering analysis of the full spectroscopically identified database (392 active galactic nuclei [AGNs]). The clustering signal at 0.02<z<0.22 is detected at a 3-4 σ level, and its amplitude is measured to be r₀=8.6+/-2.0h^-1 Mpc (in a Λ cold dark matter [ΛCDM] model). The comparison with other classes of objects shows that low-redshift QSOs are clustered in a way similar to radio galaxies, extremely red objects (EROs), and early-type galaxies in general, although with a marginally smaller amplitude. The comparison with recent results from the Two Degree Field (2dF) QSO Redshift Survey (2QZ) shows that the correlation function of QSOs is constant in redshift or marginally increasing toward low redshift. We discuss this behavior with physically motivated models, deriving interesting constraints on the typical mass of the dark matter halos hosting QSOs, M_DMH~10^12.7h^-1M_solar (10^12.0-10^13.5h^-1M_solar at 1 σ confidence level). Finally, we use the clustering data to infer the physical properties of local AGNs, obtaining M_BH~2×10⁸h^-1M_solar (1×10⁷-3×10⁹h^-1M_solar) for the mass of the active black holes, τ_AGN~8×10⁶ yr (2×10⁶-5×10⁷ yr) for their lifetime and η~0.14 for their efficiency (always for a ΛCDM model).

Based on observations collected at the European Southern Observatory, Chile (ESO P66.A-0277 and ESO P67.A-0537), with the Steward Observatory in Arizona and the National Telescope Galileo (TNG) during period AO3.