Identification of New Gamma-ray Blazars Using Fermi-LAT

We study sources with WISE-IR colours similar to those of known blazars and with radio counterparts from NVSS and SUMSS catalogues (WIBR catalogue). Besides, we study gamma-ray blazars which are part of the upcoming 2BIGB catalogue. Most of these sources have not yet been detected in any of the current Fermi-LAT catalogues including the 4FGL. This study, therefore, aimed at identifying new gamma-ray blazars by using Fermi science tools. The new blazar candidates were identified by analysing their spectral energy distribution. From the WIBR catalogue, a total of 230 sources (WIBR-Selection) were analysed for their spectral energy distribution (SED) to identify blazar candidates from which we selected 40 sources for the gamma-ray analysis. A binned likelihood analysis (at the 500 MeV–500 GeV energy band) integrating over 10 years of Fermi-LAT observations were performed to determine the statistical significance of the gamma-ray detections. By studying the test statistics (TS) maps, we confirm the new gamma-ray detections and also solve cases of source confusion. Out of the subsample of 40 WIBR sources, 26 sources (65%) have shown significant gamma-ray signatures ≥ 3σ. Among the significant detections from WIBR sources, 8 sources are completely new gamma-ray sources from the TS map analysis and 18 sources were found to be spurious detections. Given a large number of sky regions studied with TS maps, we also identified 25 new unknown gamma-ray sources which happen to be close to our seed positions. These results show that a multi-frequency approach improves our current description of the gamma-ray sky, making it a powerful tool to explore very high energy (VHE) phenomena in astrophysics.