CRATES: An All‐Sky Survey of Flat‐Spectrum Radio Sources

TLDR

CRATES is a survey targeting bright flat‑spectrum radio sources across the extragalactic sky. The study aims to describe the morphology and spectral‑index distribution of the sample and assess its utility for selecting high‑energy blazars. The authors compiled an 8.4 GHz catalog of bright flat‑spectral sources (S₄.₈ GHz > 65 mJy) by combining CLASS, PMN‑CA, archival VLA/ATCA data, and new observations to achieve uniform extragalactic coverage. The catalog contains ~11,000 sources with precise positions, sub‑arcsecond structures, and spectral indices, enabling identification of high‑power radio sources and facilitating comparison with other high‑frequency surveys.

Abstract

We have assembled an 8.4 GHz survey of bright, flat-spectrum (alpha > -0.5) radio sources with nearly uniform extragalactic (|b|>10 deg) coverage for sources brighter than S_{4.8 GHz} = 65 mJy. The catalog is assembled from existing observations (especially CLASS and the Wright et al. PMN-CA survey), augmented by reprocessing of archival VLA and ATCA data and by new observations to fill in coverage gaps. We refer to this program as CRATES, the Combined Radio All-sky Targeted Eight GHz Survey. The resulting catalog provides precise positions, sub-arcsecond structures, and spectral indices for some 11,000 sources. We describe the morphology and spectral index distribution of the sample and comment on the survey's power to select several classes of interesting sources, especially high energy blazars. Comparison of CRATES with other high-frequency surveys also provides unique opportunities for identification of high-power radio sources.