Two new catalogs of blazar candidates in the WISE infrared sky

Abstract

We present two catalogs of radio-loud candidate blazars whose WISE mid-infrared colors are selected to be consistent with the colors of confirmed gamma-ray emitting blazars. The first catalog is the improved and expanded release of the WIBRaLS catalog presented by D'Abrusco et al. (2014): it includes sources detected in all four WISE filters, spatially cross-matched with radio source in one of three radio surveys and radio-loud based on their q22 spectral parameter. WIBRaLS2 includes 9541 sources classified as BL Lacs, FSRQs 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, gamma-ray BL Lacs. KDBLLACS members area also required to have a radio counterpart and be radio-loud based on the parameter q12, defined similarly to q22 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 crossmatch the two new catalogs with the most recent catalogs of gamma-ray sources detected by Fermi LAT instrument. Since spectroscopic observations of candidate blazars from the first WIBRaLS catalog within the uncertainty regions of gamma-ray unassociated sources confirmed that ~90% of these candidates are blazars, we anticipate that these new catalogs will play again an important role in the identification of the gamma-ray sky.