The Case for an Optically-Thick High-Velocity Broad-Line Region

Authors

Stephanie A. Snedden, New Mexico State UniversityFollow
C. Martin Gaskell, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2-1-2004

Comments

Submitted to Astrophysical Journal (2006). Copyright 2004 Stephanie A. Snedden and C. Martin Gaskell.

Abstract

A combined analysis of the profiles of the main broad quasar emission lines in both Hubble Space Telescope and optical spectra shows that while the profiles of the strong UV lines are quite similar, there is frequently a strong increase in the Lyα/Hα ratio in the high-velocity gas. We show that the suggestion that the high velocity gas is optically-thin presents many problems. We show that the relative strengths of the high velocity wings arise naturally in an optically-thick BLR component. An optically-thick model successfully explains the equivalent widths of the lines, the Lyα/Hα ratios and flatter Balmer decrements in the line wings, the strengths of CIII] and the λ1400 blend, and the strong variability of high-velocity, high-ionization lines (especially He II and He I).