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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 730158.0, MPI für Astronomie / Publikationen_mpia
Mining for dust in type 1 quasars
Authors:Krawczyk, C. M.; Richards, G. T.; Gallagher, S. C.; Leighly, K. M.; Hewett, P. C.; Ross, N. P.; Hall, P. B.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:The Astronomical Journal
Issue / Number:6
Start Page:id. 203 (20 pp)
Audience:Not Specified
Abstract / Description:We explore the extinction/reddening of ˜35,000 uniformly selected quasars with 0\lt z≤slant 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)\gt 0.1 and 0.1% (1.3%) with E(B-V)\gt 0.2. Simulations show both populations of quasars are intrinsically bluer than the mean composite, with a mean spectral index ({{α }λ }) 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.
Free Keywords:dust; extinction; infrared: galaxies; methods: statistical; quasars: absorption lines; quasars: emission lines; quasars: general
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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