Unveiling the nature of the unidentified gamma-ray sources VI: gamma-ray blazar candidates in the WISH survey and their radio properties

TL;DR

This study identifies potential gamma-ray blazar counterparts among unidentified sources using low-frequency radio surveys, revealing new associations and analyzing their spectral properties to improve understanding of gamma-ray source counterparts.

Contribution

The paper introduces a novel method of associating gamma-ray sources with blazar candidates using low-frequency radio data, expanding the identification techniques for unidentified gamma-ray sources.

Findings

Proposed new associations for eight unidentified gamma-ray sources.

Found significant differences in radio flux distributions between candidate and known blazars.

Discussed the applicability of the method to future surveys and other sky regions.

Abstract

According to the second Fermi LAT Catalog (2FGL), about one third of the gamma-ray sources listed have no assigned counterparts at lower energies. Many statistical methods have been developed to find proper counterparts for these sources. We explore the sky area covered at low radio frequency by Westerbork in the Southern Hemisphere (WISH) survey to search for blazar-like associations among the unidentified gamma-ray sources listed in the 2FGL (UGSs). Searching the WISH and NRAO VLA Sky Survey (NVSS) radio surveys within the positional uncertainty regions of the 2FGL UGSs, we select as gamma-ray blazar candidates the radio sources characterized by flat radio spectra between 352 MHz and 1400 MHz. We propose new gamma-ray blazar associations for eight UGSs and we also discuss their spectral properties at low radio frequencies. We compare the radio flux density distribution of the low radio frequency gamma-ray blazar candidates with that of gamma-ray blazars associated with other methods. We find significant differences between these distributions. Finally, we discuss the results of this association method and its possible applicability to other regions of the sky and future radio surveys.