A Very Large Array Survey of Radio-Selected SDSS Broad Absorption Line Quasars

Abstract

We have built a sample of 74 radio-selected broad absorption line quasars from the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) and Faint Images of the Radio Sky at Twenty Centimeters (FIRST), along with a well matched sample of 74 unabsorbed "normal" quasars. The sources have been observed with the NRAO Very Large Array/Expanded Very Large Array at 8.4 GHz (3.5 cm) and 4.9 GHz (6 cm). All sources have additional archival 1.4 GHz (21 cm) data. Here we present the measured radio fluxes, spectral indices, and our initial findings. The percentage of BAL quasars with extended structure (on the order of 10%) in our sample is similar to previous studies at similar resolutions, suggesting that BAL quasars are indeed generally compact, at least at arsecond resolutions. The majority of sources do not appear to be significantly variable at 1.4 GHz, but we find two previously unidentified BAL quasars that may fit into the "polar" BAL category. We also identify a significant favoring of steeper radio spectral index for BAL compared to non-BAL quasars. This difference is apparent for several different measures of the spectral index, and persists even when restricting the samples to only include compact objects. Because radio spectral index is a statistical indicator of viewing angle for large samples, these results suggest that BAL quasars do have a range of orientations but are more often observed farther from the jet axis compared to normal quasars.

The parsec-scale structure of radio-loud broad absorption line quasars

“…The bipolar wind model proposed by Punsly (1999a,b) was used by Ghosh & Punsly (2007) to explain the polar BAL QSOs found by Zhou et al (2006): in this model the BAL outflow would be aligned with the polar axis, while the relativistic jet would be nested inside of it. Recent works, based on large samples, do not confirm a young age for all BAL QSOs, but also a variety of orientations have been found (Bruni et al 2012;DiPompeo et al 2011). Also, on the arcsec-scale the majority of these sources remain unresolved in the radio band, with only about 10% or less showing an extended morphology (Bruni et al 2012;DiPompeo et al 2011).…”

“…Recent works, based on large samples, do not confirm a young age for all BAL QSOs, but also a variety of orientations have been found (Bruni et al 2012;DiPompeo et al 2011). Also, on the arcsec-scale the majority of these sources remain unresolved in the radio band, with only about 10% or less showing an extended morphology (Bruni et al 2012;DiPompeo et al 2011).…”

On the origins of C iv absorption profile diversity in broad absorption line quasars

“…Becker et al (2000) find a LoBALQ fraction of ≃0.5 in the FIRST BALQ sample, compared to ∼0.1 found in SDSS samples that are dominated by RQ BALQs. DiPompeo et al (2011) report that RL BALQs are typically viewed at larger angles relative to the radio-jet axis compared to RL nonBALQs. This supports the interpretation of αUV as an inclination angle indicator, where a redder αUV implies a larger angle, since the radio-jet axis is likely to be perpendicular to the symmetry plane of the system.…”

Investigating the radio-loud phase of broad absorption line quasars

“…Becker et al (2000) first used the radio emission spectral index to derive the jet orientation of BAL QSOs, and noted that this can lie in wide range of possible angles. After these works, different authors presented detailed studies about larger samples of radio-loud BAL QSOs, from which they reported a variety of possible orientations for the outflow, but also a variety of possible morphologies and ages for the radio source (Montenegro-Montes et al 2008;DiPompeo et al 2011;Bruni et al 2012Bruni et al , 2013). This does not suggest a scenario that would be clearly referable to one of the proposed models.…”