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Composite Spectral Energy Distributions and Infrared-Optical Colors of Type 1 and Type 2 Quasars

Author(s): Hickox, Ryan C; Myers, Adam D; Greene, Jenny E.; Hainline, Kevin N; Zakamska, Nadia L; et al

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Abstract: We present observed mid-infrared and optical colors and composite spectral energy distributions (SEDs) of type 1 (broad-line) and 2 (narrow-line) quasars selected from Sloan Digital Sky Survey (SDSS) spectroscopy. A significant fraction of powerful quasars are obscured by dust and are difficult to detect in optical photometric or spectroscopic surveys. However, these may be more easily identified on the basis of mid-infrared (MIR) colors and SEDs. Using samples of SDSS type 1 and 2 matched in redshift and [O III] luminosity, we produce composite rest-frame 0.2-15 mu m SEDs based on SDSS, UKIDSS, and Wide-field Infrared Survey Explorer photometry and perform model fits using simple galaxy and quasar SED templates. The SEDs of type 1 and 2 quasars are remarkably similar, with the differences explained primarily by the extinction of the quasar component in the type 2 systems. For both types of quasar, the flux of the active galactic nucleus (AGN) relative to the host galaxy increases with AGN luminosity (L-[O III]) and redder observed MIR color, but we find only weak dependencies of the composite SEDs on mechanical jet power as determined through radio luminosity. We conclude that luminous quasars can be effectively selected using simple MIR color criteria similar to those identified previously (W1-W2 > 0.7; Vega), although these criteria miss many heavily obscured objects. Obscured quasars can be further identified based on optical-IR colors (for example, (u-W3[AB])> 1.4(W1-W2[Vega])+ 3.2). These results illustrate the power of large statistical studies of obscured quasars selected on the basis of MIR and optical photometry.
Publication Date: 1-Nov-2017
Electronic Publication Date: 30-Oct-2017
Citation: Hickox, Ryan C, Myers, Adam D, Greene, Jenny E, Hainline, Kevin N, Zakamska, Nadia L, DiPompeo, Michael A. (2017). Composite Spectral Energy Distributions and Infrared-Optical Colors of Type 1 and Type 2 Quasars. ASTROPHYSICAL JOURNAL, 849 (10.3847/1538-4357/aa8c77
DOI: doi:10.3847/1538-4357/aa8c77
ISSN: 0004-637X
EISSN: 1538-4357
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Type of Material: Journal Article
Journal/Proceeding Title: ASTROPHYSICAL JOURNAL
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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