Dependence of the broad Fe K alpha line on the physical parameters of AGN
2016 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 463, no 1, 684-695 p.Article in journal (Refereed) Published
In this paper, the dependence of the broad Fe K alpha line on the physical parameters of AGN, such as the black hole mass M-BH, accretion rate (equivalently represented by Eddington ratio lambda(Edd)) and optical classification is investigated by applying the X-ray spectra stacking method to a large sample of AGN which have well measured optical parameters. A broad-line feature is detected (> 3 sigma) in the stacked spectra of the high lambda(Edd) sub-sample (log lambda(Edd) > -0.9). The profile of the broad line can be well fitted with relativistic broad-line model, with the line energy consistent with highly ionized Fe K alpha line (i.e. Fe xxvi). A model consisting of multiple narrow lines cannot be ruled out, however. We found hints that the Fe K line becomes broader as the lambda(Edd) increases. No broad-line feature is shown in the sub-sample of broad-line Seyfert 1 (BLS1) galaxies and in the full sample, while a broad line might be present, though at low significance, in the sub-sample of narrow-line Seyfert 1 (NLS1) galaxies. We find no strong dependence of the broad line on black hole masses. Our results indicate that the detection/properties of the broad Fe K alpha line may strongly depend on lambda(Edd), which can be explained if the ionization state and/or truncation radius of the accretion disc changes with lambda(Edd). The non-detection of the broad line in the BLS1 sub-sample can be explained if the average equivalent width of the relativistic Fe K alpha line is weak or/and the fraction of sources with relativistic Fe K alpha line is small in BLS1 galaxies.
Place, publisher, year, edition, pages
2016. Vol. 463, no 1, 684-695 p.
galaxies: active, X-rays: galaxies
IdentifiersURN: urn:nbn:se:kth:diva-196971DOI: 10.1093/mnras/stw2042ISI: 000386464900055OAI: oai:DiVA.org:kth-196971DiVA: diva2:1056015
QC 201612132016-12-132016-11-282016-12-13Bibliographically approved