2018A&A...620A..17P

The XMM-XXL Survey spans two fields of 25 deg² each observed for more than 6 Ms with XMM, which provided a sample of tens of thousands of point sources with a flux limit of ∼2.2x10^–15 and ∼1.4x10^–14erg/s/cm², corresponding to 50% of the area curve, in the soft band (0.5-2keV) and hard band (2-10keV), respectively. In this paper we present the spatial clustering properties of ∼3100 and ∼1900 X-ray active galactic nuclei (AGNs) in the soft and hard bands, respectively, which have been spectroscopically observed with the AAOmega facility. This sample is 90% redshift complete down to an optical magnitude limit of r≤21.8. The sources span the redshift interval 0<z<5.2, although in the current analysis we limit our samples to z≤3, with corresponding sample median values of {bar}z~=0.96 and 0.79 for the soft band and hard band, respectively. We employ the projected two-point correlation function to infer the spatial clustering and find a correlation length r₀=7.0(±0.34) and 6.42(±0.42)h^–1Mpc, respectively, for the soft- and hard-band detected sources with a slope for both cases of γ=1.44(±0.1). The power-law clustering was detected within comoving separations of 1 and ∼25h^–1Mpc. These results, as well as those derived in two separate redshift ranges, provide bias factors of the corresponding AGN host dark matter halos that are consistent with a halo mass of log₁₀[M_h/(h^–1M_☉)]=13.04±0.06, confirming the results of most recent studies based on smaller X-ray AGN samples.