Spectral Energy Distributions of Hard X‐Ray Selected Active Galactic Nuclei in theXMM‐NewtonMedium Deep Survey

We present the spectral energy distributions (SEDs) of a hard X-ray selectedsample. The sample contains 136 sources with F(2-10 keV)>10^-14 erg/cm^2/s and132 are AGNs. The sources are detected in a 1 square degree area of theXMM-Newton-Medium Deep Survey where optical data from the VVDS, CFHTLS surveys,and infrared data from the SWIRE survey are available. Based on a SED fittingtechnique we derive photometric redshifts with sigma(1+z)=0.11 and 6% ofoutliers and identify AGN signatures in 83% of the objects. This fraction ishigher than derived when a spectroscopic classification is available. Theremaining 17+9-6% of AGNs shows star-forming galaxy SEDs (SF class). Thesources with AGN signatures are divided in two classes, AGN1 (33+6-1%) and AGN2(50+6-11). The AGN1 and AGN2 classes include sources whose SEDs are fitted bytype 1 and type 2 AGN templates, respectively. On average, AGN1s show softX-ray spectra, consistent with being unabsorbed, while AGN2s and SFs show hardX-ray spectra, consistent with being absorbed. The analysis of the average SEDsas a function of X-ray luminosity shows a reddening of the IR SEDs, consistentwith a decreasing contribution from the host galaxy at higher luminosities. TheAGNs in the SF classes are likely obscured in the mid-infrared, as suggested bytheir low L(3-20micron)/Lcorr(0.5-10 keV) ratios. We confirm the previouslyfound correlation for AGNs between the radio luminosity and the X-ray and themid-infrared luminosities. The X-ray-radio correlation can be used to identifyheavily absorbed AGNs. However, the estimated radio fluxes for the missing AGNpopulation responsible for the bulk of the background at E>10 keV are too faintto be detected even in the deepest current radio surveys.Comment: Accepted for publication in Ap