Clues to Quasar Broad-Line Region Geometry and Kinematics

Abstract

We present evidence that the high-velocity C IV λ1549 emission-line gas of radio-loud quasars may originate in a disklike configuration, in close proximity to the accretion disk often assumed to emit the low-ionization lines. For a sample of 36 radio-loud z ≈ 2 quasars, we find the 20%-30% peak widths to show significant inverse correlations with the fractional radio core-flux density R, which is the radio axis inclination indicator. Highly inclined systems have broader line wings, consistent with a high-velocity field perpendicular to the radio axis. By contrast, the narrow line core shows no such relation with R, so the lowest velocity C IV-emitting gas has an inclination-independent velocity field. We propose that this low-velocity gas is located at higher disk altitudes than the high-velocity gas. A planar origin of the high-velocity C IV emission is consistent with the current results and with an accretion disk wind emitting the broad lines. A spherical distribution of randomly orbiting broad-line clouds and a polar high-ionization outflow are ruled out.