An Infrared Excess Identified in Radio-Loud Broad Absorption Line
  Quasars
  If broad absorption line (BAL) quasars represent a high covering fraction
evolutionary state (even if this is not the sole factor governing the presence
of BALs), it is expected that they should show an excess of mid-infrared
radiation compared to normal quasars. Some previous studies have suggested that
this is not the case. We perform the first analysis of the IR properties of
radio-loud BAL quasars, using IR data from WISE and optical (rest-frame
ultraviolet) data from SDSS, and compare the BAL quasar sample with a
well-matched sample of unabsorbed quasars. We find a statistically significant
excess in the mid- to near-infrared luminosities of BAL quasars, particularly
at rest-frame wavelengths of 1.5 and 4 microns. Our sample was previously used
to show that BALs are observed along many lines of sight towards quasars, but
with an overabundance of more edge-on sources, suggesting that orientation
factors into the appearance of BALs. The evidence here---of a difference in IR
luminosities between BAL quasars and unabsorbed quasars---may be ascribed to
evolution. This suggests that a merging of the current BAL paradigms is needed
to fully describe the class.
