We explore the extinction/reddening of \sim 35,000 uniformly selected quasars with 0 < z \leq 5.3 in order to better understand their intrinsic optical/ultraviolet ( UV ) spectral energy distributions .
Using rest-frame optical–UV photometry taken from the Sloan Digital Sky Survey ’ s ( SDSS ) 7th data release , cross-matched to WISE in the mid-infrared , 2MASS and UKIDSS in the near-infrared , and GALEX in the UV , we isolate outliers in the color distribution and find them well described by an SMC-like reddening law .
A hierarchical Bayesian model with a Markov Chain Monte Carlo sampling method was used to find distributions of powerlaw indices and { E ( B - V ) } consistent with both the broad absorption line ( BAL ) and non-BAL samples .
We find that , of the ugriz color-selected type 1 quasars in SDSS , 2.5 % ( 13 % ) of the non-BAL ( BAL ) sample are consistent with { E ( B - V ) } > 0.1 and 0.1 % ( 1.3 % ) with { E ( B - V ) } > 0.2 .
Simulations show both populations of quasars are intrinsically bluer than the mean composite , with a mean spectral index ( \alpha _ { \lambda } ) of -1.79 ( -1.83 ) .
The emission and absorption-line properties of both samples reveal that quasars with intrinsically red continua have narrower Balmer lines and stronger high-ionization emission lines , the latter indicating a harder continuum in the extreme-UV and the former pointing to differences in black hole mass and/or orientation .