A Subset of Quasars Identified by Large Values of Their Doppler Redshift

• Published in: The Astrophysical journal Vol. 669; no. 1; pp. 74 - 84
• Main Authors: Lü, L.-Z, Qin, Y.-P, Gupta, A. C
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 01-11-2007; University of Chicago Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Statistical method; Quasars; Absorption line; Red shift; methods: statistical; quasars: emission lines; quasars: general; quasars: absorption lines; catalogs; Astronomical catalogues; Emission line
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/521324

We have calculated the Doppler redshlfts for a sample of quasars from their observed emission and absorption redshifts. We selected only those absorption redshifts that are larger than the corresponding emission redshifts (i.e., [unk] > [unk]). The sample was extracted from a quasar catalog that contains spectra of 784 quasars, for which 11,298 absorption systems and 20,837 absorption lines were detected. We obtained 256 absorption systems with [unk] > [unk] from 123 quasars. We find that there is a bimodal structure in the distribution of the Doppler redshifts, with one peak being located at [unk] [unk] 0.00 and the other at [unk] [unk] 0.01. Around the second peak, [unk] [unk] 0.01, we identify a subset of quasars with Doppler redshifts greater than 0.0088. Our analysis shows that quasars in this subset are generally brighter than those with Doppler redshifts less than 0.0088. The Doppler velocities of the absorbers of these quasars are concentrated around similar to 3000 km s super(-1). This velocity likely arises from material falling toward the central region of the quasars that originates beyond the torus.