We present the SEDs of a hard X-ray selected sample containing 136 sources with F 2Y10 keV > 10 À14 erg cm À2 s À1 ; 132 are AGNs. The sources are detected in a 1 deg 2 area of the XMM-Newton Medium Deep Survey where optical data from the VVDS and CFHTLS and infrared data from the SWIRE survey are available. Based on a SED fitting technique we derive photometric redshifts with (1 þ z) ¼ 0:11 and 6% of outliers and identify AGN signatures in 83% of the objects. This fraction is higher than derived when a spectroscopic classification is available. The remaining 17 þ9 À6 % of AGNs show star-forming galaxy SEDs (SF class). The sources with AGN signatures are divided in two classes, AGN1 (33 þ6 À1 %) and AGN2 (50 þ6 À11 %). The AGN1 and AGN2 classes include sources whose SEDs are fitted by type 1 and type 2 AGN templates, respectively. On average, AGN1s show soft X-ray spectra, consistent with being unabsorbed, while AGN2s and SFs show hard X-ray spectra, consistent with being absorbed. The analysis of the average SEDs as a function of X-ray luminosity shows a reddening of the infrared SEDs, consistent with a decreasing contribution from the host galaxy at higher luminosities. The AGNs in the SF classes are likely obscured in the mid-infrared, as suggested by their low L 3Y20 m /L corr 0:5Y10 keV ratios. We confirm the previously found correlation for AGNs between the radio luminosity and the X-ray and the mid-infrared luminosities. The X-rayYradio correlation can be used to identify heavily absorbed AGNs. However, the estimated radio fluxes for the missing AGN population responsible for the bulk of the background at E > 10 keV are too faint to be detected even in the deepest current radio surveys.

We present the X‐ray pipeline developed for the purpose of the cluster search in the XMM Large‐Scale Structure (XMM‐LSS) survey. It is based on a two‐stage procedure via a dedicated handling of the Poisson nature of the signal: (i) source detection on multiresolution wavelet filtered images and (ii) source analysis by means of a maximum likelihood fit to the photon images. The source detection efficiency and characterization are studied through extensive Monte Carlo simulations. This led us to define two samples of extended sources: the C1 class that is uncontaminated, and the less restrictive C2 class that allows for 50 per cent contamination. The resulting predicted selection function is presented and the comparison to the current XMM‐LSS confirmed cluster sample shows very good agreement. We arrive at average predicted source densities of about seven C1 and 12 C2 per deg2, which is higher than any available wide field X‐ray survey. We finally note a substantial deviation of the predicted redshift distribution for our samples from the one obtained using the usual assumption of a flux‐limited sample.

We present a sample of 29 galaxy clusters from the XMM‐LSS survey over an area of some 5 deg2 out to a redshift of z= 1.05. The sample clusters, which represent about half of the X‐ray clusters identified in the region, follow well‐defined X‐ray selection criteria and are all spectroscopically confirmed. For all clusters, we provide X‐ray luminosities and temperatures as well as masses, obtained from dedicated spatial and spectral fitting. The cluster distribution peaks around z= 0.3 and T= 1.5 keV, half of the objects being groups with a temperature below 2 keV. Our LX–T(z) relation points towards self‐similar evolution, but does not exclude other physically plausible models. Assuming that cluster scaling laws follow self‐similar evolution, our number density estimates up to z= 1 are compatible with the predictions of the concordance cosmology and with the findings of previous ROSAT surveys. Our well‐monitored selection function allowed us to demonstrate that the inclusion of selection effects is essential for the correct determination of the evolution of the LX–T relation, which may explain the contradictory results from previous studies. Extensive simulations show that extending the survey area to 10 deg2 has the potential to exclude the non‐evolution hypothesis, but those constraints on more refined intracluster medium models will probably be limited by the large intrinsic dispersion of the LX–T relation, whatever be the sample size. We further demonstrate that increasing the dispersion in the scaling laws increases the number of detectable clusters, hence generating further degeneracy [in addition to σ8, Ωm, LX–T(z)] in the cosmological interpretation of the cluster number counts. We provide useful empirical formulae for the cluster mass–flux and mass–count rate relations as well as a comparison between the XMM‐LSS mass sensitivity and that of forthcoming Sunyaev–Zel'dovich surveys.

Abstract. We present a first catalogue of X-ray sources resulting from the central area of the XMM-LSS (Large Scale Structure survey). We describe the reduction procedures and the database tools we developed and used to derive a well defined catalogue of X-ray sources. The present catalogue is limited to a sub-sample of 286 sources detected at 4σ in the 1 deg 2 area covered by the photometric VVDS (VIRMOS VLT Deep Survey), which allows us to provide optical and radio identifications. We also discuss the X-ray properties of a larger X-ray sample of 536 sources detected at >4σ in the full 3 deg 2 area of the XMM Medium Deep Survey (XMDS) independently of the optical identification. We also derive the log N − log S relationship for a sample of more than one thousand sources that we discuss in the context of other surveys at similar fluxes.

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 2 × 10 −15 and 8 × 10 −15 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 ∼2 × 10 −14 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.