Journal
ASTRONOMICAL JOURNAL
Volume 149, Issue 6, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/0004-6256/149/6/203
Keywords
dust, extinction; infrared: galaxies; methods: statistical; quasars: absorption lines; quasars: emission lines; quasars: general
Categories
Funding
- Alexander von Humboldt Research Fellowship
- NASA [NNX08AJ27G, NNX10AF74G, NNX12AI49G]
- Alexander von Humboldt Foundation at the Max-Planck-Institut fur Astronomie
- Natural Science and Engineering Research Council of Canada
- National Aeronautics and Space Administration
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- STFC [ST/L00481X/1, ST/K000985/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/L00481X/1, ST/K000985/1] Funding Source: researchfish
- NASA [100889, NNX08AJ27G, 134532, NNX10AF74G, NNX12AI49G, 21500] Funding Source: Federal RePORTER
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We explore the extinction/reddening of similar to 35,000 uniformly selected quasars with 0 < z <= 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 power law 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.
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