Two New Catalogs of Blazar Candidates in the WISE Infrared Sky

Abstract

We present two catalogs of radio-loud candidate blazars whose Wide-Field Infrared Survey Explorer ( WISE ) mid-infrared colors are selected to be consistent with the colors of confirmed γ -ray-emitting blazars. The first catalog is the improved and expanded release of the WISE Blazar-like Radio-Loud Sources (WIBRaLS) catalog presented by D’Abrusco et al. It includes sources detected in all four WISE filters, spatially cross-matched with radio sources in one of three radio surveys and radio-loud based on their q 22 spectral parameter. WIBRaLS2 includes 9541 sources classified as BL Lacs, flat-spectrum radio quasars, or mixed candidates based on their WISE colors. The second catalog, called KDEBLLACS, based on a new selection technique, contains 5579 candidate BL Lacs extracted from the population of WISE sources detected in the first three WISE passbands ([3.4], [4.6], and [12]) only, whose mid-infrared colors are similar to those of confirmed, γ -ray BL Lacs. Members of KDBLLACS are also required to have a radio counterpart and be radio-loud based on the parameter q 12 , defined similarly to the q 22 used for the WIBRaLS2. We describe the properties of these catalogs and compare them with the largest samples of confirmed and candidate blazars in the literature. We cross-match the two new catalogs with the most recent catalogs of γ -ray sources detected by the Fermi Large Area Telescope. Since spectroscopic observations of candidate blazars from the first WIBRaLS catalog within the uncertainty regions of γ -ray unassociated sources confirmed that ∼90% of these candidates are blazars, we anticipate that these new catalogs will again play an important role in the identification of the γ -ray sky.