The clustering of X-ray-selected active galactic nuclei at z= 0.1




The clustering properties of moderate-luminosity (inline image) X-ray-selected active galactic nuclei (AGN) at z≈ 0.1 are explored. X-ray sources in the redshift interval 0.03 < z < 0.2 are selected from a serendipitous XMM survey of the Sloan Digital Sky Survey (SDSS) footprint (XMM/SDSS) and are cross-correlated with the SDSS main galaxy sample. The inferred X-ray AGN autocorrelation function is described by a power law with amplitude r0≈ 5 h−1 Mpc and slope γ≈ 2.0. The corresponding mass of the dark matter haloes that host X-ray AGN at z≈ 0.1 is inline image. Comparison with studies at higher redshift shows that this mass scale is characteristic of moderate-luminosity X-ray AGN out to z≈ 1. Splitting the AGN sample by rest-frame colour shows that X-ray sources in red hosts are more clustered than those associated with blue galaxies, in agreement with results at z≈ 1. We also find that the host galaxies of X-ray AGN have lower stellar masses compared to the typical central galaxy of a dark matter halo of inline image. AGN hosts either have experienced less stellar mass growth compared to the average central galaxy of a halo of ≈1013 h−1 M or a fraction of them are associated with satellite galaxies.