Spectral energy distributions of hard X-ray selected active galactic nuclei in the XMM-Newton Medium Deep Survey

We present the SEDs of a hard X- ray selected sample containing 136 sources with F-2Y10 (keV) > 10(-14) erg cm(-2) s(-1); 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 sigma(1 + z) = 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(-6)(+9) % of AGNs show star-forming galaxy SEDs ( SF class). The sources with AGN signatures are divided in two classes, AGN1 ( 33(-1)(+6)%) and AGN2 ( 50(-11)(+6)%). 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 L3-20 mu m/ L-0.5-10 keV(corr) ratios. We confirm the previously found correlation for AGNs between the radio luminosity and the X-ray and the mid- infrared luminosities. The X- ray-radio 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 keVare too faint to be detected even in the deepest current radio surveys.