Radio-Loud and Radio-Quiet BAL Quasars: A Detailed Ultraviolet Comparison

TL;DR

This study compares the ultraviolet spectral properties of radio-loud and radio-quiet broad absorption line quasars, finding mostly similar characteristics and suggesting they are driven by similar physical mechanisms.

Contribution

It extends previous analyses to UV properties, showing that RL and RQ BAL quasars are largely similar, with only subtle differences, thus supporting unified models.

Findings

Most properties are statistically identical between RL and RQ BAL quasars.

Slight differences in BAL velocity structures suggest possible jet interactions.

UV FeII emission is marginally stronger in RL BAL quasars.

Abstract

Studies of radio-loud (RL) broad absorption line (BAL) quasars indicate that popular orientation-based BAL models fail to account for all observations. Are these results extendable to radio-quiet (RQ) BAL quasars? Comparisons of RL and RQ BAL quasars show that many of their properties are quite similar. Here we extend these analyses to the rest-frame ultraviolet (UV) spectral properties, using a sample of 73 RL and 473 RQ BAL quasars selected from the Sloan Digital Sky Survey (SDSS). Each RQ quasar is individually matched to a RL quasar in both redshift (over the range $1.5 < z < 3.5$) and continuum luminosity. We compare several continuum, emission line, and absorption line properties, as well as physical properties derived from these measurements. Most properties in the samples are statistically identical, though we find slight differences in the velocity structure of the BALs that cause apparent differences in CIV emission line properties. Differences in the velocities may indicate an interaction between the radio jets and the absorbing material. We also find that UV FeII emission is marginally stronger in RL BAL quasars. All of these differences are subtle, so in general we conclude that RL and RQ BAL QSOs are not fundamentally different objects, except in their radio properties. They are therefore likely to be driven by similar physical phenomena, suggesting that results from samples of RL BAL quasars can be extended to their RQ counterparts.