A Large Population of Mid-Infrared-selected, Obscured Active Galaxies in the Boötes Field

Citation:

Hickox RC, Jones C, Forman WR, Murray SS, Brodwin M, Brown MJI, Eisenhardt PR, Stern D, Kochanek CS, Eisenstein D. A Large Population of Mid-Infrared-selected, Obscured Active Galaxies in the Boötes Field. The Astrophysical Journal [Internet]. 2007;671:1365-1387.

Abstract:

We identify a population of 640 obscured and 839 unobscured AGNs atredshifts 0.72 NOAO Deep Wide-Field Survey (NDWFS) region inBoötes. We select AGNs on the basis of Spitzer IRAC colors obtainedby the IRAC Shallow Survey. Redshifts are obtained from opticalspectroscopy or photometric redshift estimators. We classify theIR-selected AGNs as IRAGN 1 (unobscured) and IRAGN 2 (obscured) using asimple criterion based on the observed optical to mid-IR color, with aselection boundary of R-[4.5]=6.1, where R and [4.5] are the Vegamagnitudes in the R and IRAC 4.5 μm bands, respectively. We verifythis selection using X-ray stacking analyses with data from the ChandraXBoötes survey, as well as optical photometry from NDWFS andspectroscopy from MMT/AGES. We show that (1) these sources are indeedAGNs, and (2) the optical/IR color selection separates obscured sources(with average NH~3×1022 cm-2obtained from X-ray hardness ratios, and optical colors and morphologiestypical of galaxies) and unobscured sources (with no X-ray absorption,

Notes:

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