SPECTRAL ENERGY DISTRIBUTIONS OF HARD X-RAY SELECTED ACTIVE GALACTIC NUCLEI IN THE XMM-NEWTON MEDIUM DEEP SURVEY

摘要

We present the SEDs of a hard X-ray selected sample containing 136 sources with F_(2-10 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 σ(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 unab-sorbed, 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_(3-20 μm)/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 keV are too faint to be detected even in the deepest current radio surveys.