Searching for new gamma-ray blazar candidates in the 3rd Palermo BAT Hard X-ray Catalog with WISE

TL;DR

This study identifies 24 potential gamma-ray blazar candidates by cross-matching hard X-ray sources with infrared and radio data, using a novel association method based on WISE infrared colors.

Contribution

The paper introduces a new infrared color-based association method to identify gamma-ray blazar candidates among unidentified hard X-ray sources.

Findings

Identified 24 gamma-ray blazar candidates.

Developed a new infrared color-based association technique.

Enhanced candidate selection by multi-wavelength data analysis.

Abstract

We searched for gamma-ray blazar candidates among the 382 unidentified hard X-ray sources of the 3rd Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of SWIFT-BAT survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors which characterize the gamma-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope (2LAC). We used this method exploiting the data of the all-sky survey performed by the Wide-Field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE gamma-ray blazar candidates located within the BAT positional uncertainty region at 99% confidence level. We obtained a preliminary list of candidates for which we analysed all the available data in the SWIFT archive to complement the information in the literature and in the radio, infrared and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 gamma-ray blazar candidates.