Narrow Fe Ka emission within bright AGN

Finally, we extracted Chandra radial profiles to place upper limits on RFeK{alpha}. For 90% (21/24) of AGN with FWHM measurements, RFeK{alpha} is smaller than the fiducial dust sublimation radius, Rsub. From timing analysis, 37 and 18 AGN show significant continuum and Fe K{alpha} variability, respectively.

Despite a wide range of variability properties, the constraints on the Fe K{alpha} photon reprocessor size independently confirm that RFeK{alpha} is smaller than Rsub in 83% of AGN. Finally, the imaging analysis yields loose upper limits for all but two sources; notably, the Circinus Galaxy and NGC 1068 show significant but subdominant extended Fe K{alpha} emission out to ~100 and ~800pc, respectively. Based on independent constraints, we conclude that the majority of the narrow Fe K{alpha} emission in typical AGN predominantly arises from regions smaller than and presumably inside Rsub, and thus it is associated either with the outer broad line region or outer accretion disk.

However, the large diversity of continuum and narrow Fe K{alpha} variability properties are not easily accommodated by a universal scenario.