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Narrow Iron K$α$ Lines in Active Galactic Nuclei: Evolving Populations?

Xin-Lin Zhou·Jian-Min Wang
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Abstract

We assemble a sample consisting of 66 active galactic nuclei (AGNs) from literature and the {\em XMM-Newton} archive in order to investigate the origin of the 6.4 keV narrow iron K$α$ 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 ($\ce$) 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 $EW-\ce$ 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 {\sc ii} AGNs to the total population given by {\em Chandra} and {\em Hubble} deep surveys. Thus the evolution of populations could be reflected by the NIKAL's Baldwin effect.

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Xin-Lin Zhou, Jian-Min Wang. 2004-12-03. Narrow Iron K$α$ Lines in Active Galactic Nuclei: Evolving Populations?. https://doi.org/10.1086/427871

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