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Date and Time of the Query: 2018-12-13 T09:30:09 PST
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For refcode 2007ApJ...666..757S:
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2007ApJ...666..757S C IV {lambda}1549 as an Eigenvector 1 Parameter for Active Galactic Nuclei Jack W. Sulentic, Rumen Bachev, Paola Marziani, C. Alenka Negrete, and Deborah Dultzin Abstract. We are exploring a spectroscopic unification for all types of broad-line emitting AGNs. The four-dimensional Eigenvector 1 (4DE1) parameter space organizes quasar diversity in a sequence primarily governed by Eddington ratio. This paper considers the role of C IV {lambda}1549 measures as 4DE1 diagnostics. We use HST archival spectra for 130 sources with S/N high enough to permit reliable C IV {lambda}1549 broad-component measures. We find a C IV {lambda}1549_BC_ profile blueshift that is strongly concentrated among (largely radio-quiet [RQ]) sources with FWHM(H{beta}_BC_)<~4000 km s^-1^ (which we call Population A). Narrow-line Seyfert 1 (NLSy1; with FWHMH{beta}<=2000 km s^-1^) sources belong to this population but do not emerge as a distinct class. The systematic blueshift, widely interpreted as arising in a disk wind/outflow, is not observed in broader line AGNs (including most radio-loud [RL] sources), which we call Population B. We find new correlations involving FWHM(C IV {lambda}1549_BC_), C IV {lambda}1549 line shift, and equivalent width only among Population A sources. Sulentic et al. suggested C IV {lambda}1549 measures enhance an apparent dichotomy between sources with FWHM(H{beta}_BC_) less and greater than 4000 km s^-1^, suggesting that it has more significance in the context of broad-line region structure than the more commonly discussed RL versus RQ dichotomy. Black hole masses computed from FWHM C IV {lambda}1549_BC_ for about 80 AGNs indicate that the C IV {lambda}1549 width is a poor virial estimator. Comparison of mass estimates derived from H{beta}_BC_ and C IV {lambda}1549 reveals that the latter show different and nonlinear offsets for Population A and B sources. A significant number of sources also show narrow-line C IV {lambda}1549 emission that must be removed before C IV {lambda}1549_BC_ measures can be made and interpreted effectively. We present a recipe for C IV {lambda}1549 narrow-component extraction. Key words: Line: Profiles, Galaxies: Quasars: Emission Lines, Galaxies: Quasars: General
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