Narrow Iron Kα Lines in Active Galactic Nuclei: Evolving Populations?
نویسندگان
چکیده
We assemble a sample consisting of 66 active galactic nuclei (AGNs) from literature and the XMM-Newton archive in order to investigate the origin of the 6.4 keV narrow iron Kα line (NIKAL). The X-ray Baldwin effect of the NIKAL is confirmed in this sample. We find the equivalent width (EW ) of the NIKAL is more strongly inversely correlated with Eddington ratio (E) than the 2-10 keV X-ray luminosity. Our sample favors the origin from the dusty torus and the X-ray Baldwin effect is caused by the changing opening angle of the dusty torus. The relation EW −E can be derived from a toy model of the dusty torus. If the unification scheme is valid in all AGNs, we can derive the Baldwin effect from the fraction of type II AGNs to the total population given by Chandra and Hubble deep surveys. Thus the evolution of populations could be reflected by the NIKAL’s Baldwin effect. Subject headings: galaxies: active line: profile X-rays: spectra
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