Unidentifed gamma-ray sources: hunting gamma-ray blazars

TL;DR

This paper develops an infrared color-based method to identify potential gamma-ray blazar counterparts among unidentified Fermi sources, significantly improving the association rate of these elusive objects.

Contribution

The study introduces a novel IR diagnostic tool for associating gamma-ray sources with blazar candidates, enhancing identification of UGSs in the Fermi catalog.

Findings

Successfully associated 156 out of 313 UGSs with blazar candidates.

Blazar candidates exhibit IR properties consistent with known gamma-ray blazars.

Method improves the identification rate of gamma-ray blazars among UGSs.

Abstract

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified gamma-ray sources (UGSs). Despite the large improvements of Fermi in the localization of gamma-ray sources with respect to the past gamma-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-Field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of gamma-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the gamma-ray sources to reognize if there is a blazar candidate within the positional uncertainty region of a generic gamma-ray source. With this new IR diagnostic tool, we searched for gamma-ray blazar candidates associated to the UGS sample of the second Fermi gamma-ray catalog (2FGL). We found that our method associates at least one gamma-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to gamma-ray sources in the 2FGL catalog.