The Redshifted Excess in Quasar C IV Broad Emission Lines

Abstract

In this paper, the Evans and Koratkar Atlas of Hubble Space Telescope Faint Object Spectrograph Spectra of Active Galactic Nuclei and Quasars is used to study the redward asymmetry in C IV broad emission lines (BELs). It is concluded that there is a highly significant correlation between the spectral index from 10 GHz to 1350 Å and the amount of excess luminosity in the red wing of the C IV BEL (>99.9999% significance level for the full sample and the radio-loud subsample independently, but no correlation is found for the radio-quiet subsample). This is interpreted as a correlation between radio core dominance and the strength of the C IV redward asymmetry. The data imply that within the quasar environment there is BEL gas with moderately blueshifted emission associated with the purely radio-quiet quasar (RQQ) phenomenon (the accretion disk), and the radio jet emission mechanism is associated with a redward BEL component that is most prominent for lines of sight along the jet axis. Thus, RQQs have C IV BELs that tend to show blueshifted excess, and radio-loud quasars show either a red or blue excess with the tendency for a dominant red excess increasing as the line-of-sight approaches the jet axis.