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

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.

8 pages, 4 figures, 4 tables, ApJS published in 2014 (pre-proof version uploaded)

References in corpus (3)

• Roma-BZCAT: A multifrequency catalogue of Blazars
• CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
• Unveiling the nature of the unidentified gamma-ray sources IV: the $\text{Swift}$ catalog of potential X-ray counterparts

Cited by in corpus (27)

• Two new catalogs of blazar candidates in the WISE infrared sky
• Optical spectroscopic observations of blazars and gamma-ray blazar candidates in the Sloan Digital Sky Survey Data Release Nine
• Optical spectroscopic observations of gamma-ray blazar candidates II. The 2013 KPNO campaign in the Northern Hemisphere
• Optical spectroscopic observations of gamma-ray blazar candidates III. The 2013/2014 campaign in the Southern Hemisphere
• Forecasts on Primordial non-Gaussianity from 21 cm Intensity Mapping experiments
• The Gamma-ray Blazar Quest: new optical spectra, state of art and future perspectives
• Optical spectroscopic observations of gamma-ray blazar candidates IV. Results of the 2014 follow-up campaign
• Refining the associations of the Fermi Large Area Telescope Source Catalogs
• Optical spectroscopic survey of a sample of Unidentified Fermi objects
• Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. VII. Follow-up Campaign in the Southern Hemisphere
• The low-frequency radio catalog of flat spectrum sources
• Optical spectroscopic observations of gamma-ray blazar candidates VIII: the 2016-2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR telescopes
• An optical overview of blazars with LAMOST I: Hunting changing-look blazars and new redshift estimates
• Radio Weak BL Lac objects in the Fermi era
• $\mathrm{S}\mathrm{IM}\mathrm{BIG}$: Mock Challenge for a Forward Modeling Approach to Galaxy Clustering
• Optical spectroscopic observations of gamma-ray blazar candidates. IX. Optical archival spectra and further observations from SOAR and OAGH
• Local primordial non-Gaussianity in the relativistic galaxy bispectrum
• Optical spectroscopic observations of low-energy counterparts of Fermi-LAT gamma-ray sources
• ZBLLAC -- A spectroscopic database of BL Lacertae objects
• The $\gamma$-ray sky seen at X-ray energies I. Searching for the connection between X-rays and $\gamma$-rays in Fermi BL Lac objects
• VLBA observations of radio faint Fermi-LAT sources above 10 GeV
• The $\gamma$-ray sky seen at X-ray energies II: the Swift hunt of Fermi BL Lac objects among unidentified gamma-ray sources
• Evaluating Optical Classification for {\em Fermi} Blazar Candidates with a Statistical method using Broadband Spectral Indices
• Radio spectral properties of cores and extended regions in blazars in the MHz regime
• Search for the multiwavelength counterparts to extragalactic unassociated Fermi γ-ray sources
• Can supernova from runaway stars mimic the signs of absorbing `super-virial' gas?
• A FLASH on Blazars: Capturing the Radio Realm of 4FGL Blazars with SKAO Pathfinders