The XMM large scale structure survey: properties and two-point angular correlations of point-like sources

Abstract

We analyze X-ray sources detected over 4.2 pseudo-contiguous sq. deg. in the 0.5–2 keV and 2–10 keV bands down to fluxes of and erg s-1 cm-2 respectively, as part of the XMM-Newton Large Scale Structure Survey. The log N–log S in both bands shows a steep slope at bright fluxes, but agrees well with other determinations below ~ erg s-1 cm-2. The detected sources resolve close to 30 per cent of the X-ray background in the 2–10 keV band. We study the two-point angular clustering of point sources using nearest neighbours and correlation function statistics and find a weak, positive signal for ~1130 sources in the 0.5–2 keV band, but no correlation for ~400 sources in the 2–10 keV band below scales of 100 arcsec. A sub-sample of ~200 faint sources with hard X-ray count ratios, that is likely to be dominated by obscured AGN, does show a positive signal with the data allowing for a large angular correlation length, but only at the ~2 (3)σ level, based on re-sampling (Poisson) statistics. We discuss possible implications and emphasize the importance of wider, complete surveys in order to fully understand the large scale structure of the X-ray sky.