Mid-infrared Selection of Active Galactic Nuclei with the Wide-Field Infrared Survey Explorer. I. Characterizing WISE-selected Active Galactic Nuclei in COSMOS

July 2012 • 2012ApJ...753...30S

Authors • Stern, Daniel • Assef, Roberto J. • Benford, Dominic J. • Blain, Andrew • Cutri, Roc • Dey, Arjun • Eisenhardt, Peter • Griffith, Roger L. • Jarrett, T. H. • Lake, Sean • Masci, Frank • Petty, Sara • Stanford, S. A. • Tsai, Chao-Wei • Wright, E. L. • Yan, Lin • Harrison, Fiona • Madsen, Kristin

Abstract • The Wide-field Infrared Survey Explorer (WISE) is an extremely capable and efficient black hole finder. We present a simple mid-infrared color criterion, W1 - W2 >= 0.8 (i.e., [3.4]-[4.6] >=0.8, Vega), which identifies 61.9 ± 5.4 active galactic nucleus (AGN) candidates per deg² to a depth of W2 ~ 15.0. This implies a much larger census of luminous AGNs than found by typical wide-area surveys, attributable to the fact that mid-infrared selection identifies both unobscured (type 1) and obscured (type 2) AGNs. Optical and soft X-ray surveys alone are highly biased toward only unobscured AGNs, while this simple WISE selection likely identifies even heavily obscured, Compton-thick AGNs. Using deep, public data in the COSMOS field, we explore the properties of WISE-selected AGN candidates. At the mid-infrared depth considered, 160 μJy at 4.6 μm, this simple criterion identifies 78% of Spitzer mid-infrared AGN candidates according to the criteria of Stern et al. and the reliability is 95%. We explore the demographics, multiwavelength properties and redshift distribution of WISE-selected AGN candidates in the COSMOS field.

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Roc Cutri

IPAC Deputy Director