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Measures of the Soft X-ray Excess as an Eigenvector 1 Parameter for Active Galactic Nuclei

AuthorsBensch, Katarzyna; Olmo, Ascensión del ; Sulentic, Jack W. ; Perea, Jaime ; Marziani, P.
KeywordsGalaxies: active
Emission lines
Issue Date2015
PublisherIndian Academy of Sciences
CitationJournal of Astrophysics and Astronomy 36: 467- 474 (2015)
AbstractWe present a preliminary analysis of X-ray data of quasars in the context of the 4D eigenvector 1 parameter space (Sulentic et al.2000a, b). 4DE1 serves as a surrogate H-R diagram for representing empirical diversity among quasars and identifying the physical drivers of the diversity. The soft X-ray spectral index (Γ) was adopted as one of the key 4DE1 that correlates contrasting extremes in Type 1 properties. 4DE1 motivated the hypothesis of two quasar populations (A and B) divided by L/L≈0.2. Pop. A is a largely radio-quiet population with FWHM Hβ<4000 km/s and often showing a soft X-ray excess. Pop. B is a mix of radio-quiet and a majority of RL quasars shows only a hard X-ray power-law SED. The X-ray separation was based upon earlier ROSAT and ASCA data but we now confirm this dichotomy with large samples of X-ray spectra obtained with XMM-Newton and SWIFT. One popular idea connects the soft excess in Pop. A quasars as a signature of thermal emission from a hot accretion disk in sources radiating close to the Eddington limit.
Publisher version (URL)http://dx.doi.org/10.1007/s12036-015-9355-8
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