Fe K emission from active galaxies in the COSMOS field

We present a rest-frame spectral stacking analysis of ∼ 1000 X-ray sources detected in the XMM-COSMOS field in order to investigate the iron K line properties of active galaxies beyond redshift z ∼ 1. In Type I AGN that have a typical X-ray luminosity of LX ∼ 1.5 × 1044 (erg s−1) and z ∼ 1.6, the cold Fe K at 6.4 keV is weak (EW ∼ 0.05 keV), in agreement with the known trend. In contrast, high-ionization lines of Fe xxv and Fe xxvi are pronounced. These high-ionization Fe K lines appear to have a connection with high accretion rates. While no broad Fe emission is detected in the total spectrum, it might be present, albeit at low significance ( ∼ 2σ), when the X-ray luminosity is restricte