XMM-Newton observations of the Lockman Hole - III. A relativistic Fe line in the mean X-ray spectra of type-1 and type-2 AGN

Using the 770 ks XMM-Newton survey of the Lockman Hole field in combination with extensive optical identifications of the AGN population, we derive an average rest-frame spectrum of AGN types-1 and 2. The most prominent feature in the averaged spectrum is a strong fluorescent Fe line. In both type-1 and type-2 AGN, a clear relativistic line profile is revealed. A laor line profile with an inner disk radius smaller than the last stable orbit of a Schwarzschild black hole is most consistent with the data, indicating that the average supermassive black hole has significant spin. Equivalent widths of the broad relativistic lines range between 400 - 600 eV. We used the disk reflection model to compare the observed strength of the line with the amplitude of the reflection component, concluding that to consistently describe the observations the average iron abundance should be about three times the solar value.