Statistics of relativistically broadened Fe Kα lines in AGN

Abstract

We present preliminary results on the properties of relativistically broadened Fe Kα lines in a collection of more then 100 Active Galactic Nuclei (AGN) observed by the XMM-Newton EPIC-pn camera. Our main conclusions can be summarized as follows: a) we detect broad lines in about 25% of the sample objects. This fraction increases to 42 ± 13 % if we consider only objects with more than 10⁴ counts in the hard (2-10 keV) band, and to 50 ± 32 % for the small sub-sample (6 objects) of type 1 Piccinotti AGN with optimal XMM-Newton exposure (at least 2 × 10⁵ counts in the hard band); b) we find no significant difference in the detection rate of broad lines between obscured and unobscured AGN; c) the strongest relativistic profiles are measured in low-luminosity (L_X < 10⁴³ erg s^-1) AGN; d) Equivalent Widths (EWs) associated with relativistic profiles in stacked spectra are ∼150 eV for all luminosity classes; e) models of relativistically broadened iron line profiles (kyrline, \cite{dovciak05}), which include full relativistic treatment of the accretion disk emission around a Kerr black hole in the strong gravity regime, yield an average disk inclination angle ≃30^°, and a radial dependence of the disk emissivity profile ≃-3. The distribution of EW is very broad, with < log (EW) > = 2.4 and σ_{log (EW)} = 1.4. We estimate that an investment of about 1 Ms of XMM-Newton time would be required to put these results on a sound statistical basis.