The clustering of X-ray selected AGN at z=0.1

TL;DR

This study investigates the clustering behavior of moderate luminosity X-ray selected AGN at low redshift, revealing their typical dark matter halo mass and differences based on host galaxy color and stellar mass.

Contribution

It provides the first detailed clustering analysis of X-ray AGN at z≈0.1, linking their properties to dark matter halo mass and galaxy characteristics.

Findings

X-ray AGN at z≈0.1 reside in dark matter haloes of about 10^{13} h^{-1} M_sun.

Red host galaxies show stronger clustering than blue hosts.

Host galaxies of X-ray AGN have lower stellar masses than typical central galaxies in similar haloes.

Abstract

The clustering properties of moderate luminosity ($L_X = \rm 10^{41} - 10^{44} \, erg \,s^{-1}$) X-ray selected AGN at $z\approx0.1$ are explored. X-ray sources in the redshift interval $0.03<z<0.2$ are selected from a serendipitous XMM survey of the SDSS footprint (XMM/SDSS) and are cross-correlated with the SDSS Main galaxy sample. The inferred X-ray AGN auto-correlation function is described by a power law with amplitude $r_0\approx5\,$h$^{-1}$Mpc and slope $\gamma\approx2.0$. The corresponding mass of the dark matter haloes that host X-ray AGN at $z\approx0.1$ is $\approx 10^{13} \,h ^{-1} \, M_{\sun}$. Comparison with studies at higher redshift shows that this mass scale is characteristic of moderate luminosity X-ray AGN out to $z\approx 1$. Splitting the AGN sample by rest-frame color shows that X-ray sources in red hosts are more clustered than those associated with blue galaxies, in agreement with results at $z\approx1$. We also find that the host galaxies of X-ray AGN have lower stellar masses compared to the typical central galaxy of a $\approx 10^{13} \,h ^{-1} \, M_{\sun}$ dark matter halo. AGN hosts either have experienced less stellar mass growth compared to the average central galaxy of a $\approx 10^{13} \,h ^{-1} \, M_{\sun}$ halo or a fraction of them are associated with satellite galaxies.