Kavli Affiliate: Claudio Ricci
| First 5 Authors: Carolina Andonie, Franz E. Bauer, Rosamaria Carraro, Patricia Arevalo, David M. Alexander
| Summary:
The 6.4 keV Fe Ka emission line is a ubiquitous feature in X-ray spectra of
AGN, and its properties track the interaction between the variable primary
X-ray continuum and the surrounding structure from which it arises. We clarify
the nature and origin of the narrow Fe Ka emission using X-ray spectral,
timing, and imaging constraints, plus possible correlations to AGN and host
galaxy properties, for 38 bright nearby AGN ($z<0.5$) from the BAT AGN
Spectroscopic Survey. Modeling Chandra and XMM-Newton spectra, we computed line
full-width half-maxima (FWHMs) and constructed Fe Ka line and 2-10 keV
continuum light curves. The FWHM provides one estimate of the Fe Ka emitting
region size, RFeKa, assuming virial motion. A second estimate comes from
comparing the degree of correlation between the variability of the continuum
and line-only light curves, compared to simulated light curves. Finally, we
extracted Chandra radial profiles to place upper limits on RFeKa. We found that
for 90% (21/24) of AGN with FWHM measurements, RFeKa is smaller than the
fiducial dust sublimation radius, Rsub. Despite a wide range of variability
properties, the constraints on the Fe Ka photon reprocessor size independently
confirm that RFeKa 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 Ka
emission out to $sim$100 and $sim$800 pc, respectively. Based on independent
constraints, we conclude that the majority of the narrow Fe Ka 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 Ka variability properties are not easily accommodated by a universal
scenario.
| Search Query: ArXiv Query: search_query=au:”Claudio Ricci”&id_list=&start=0&max_results=10