UNVEILING THE NATURE OF THE UNIDENTIFIED γ-RAY SOURCES VI: γ-RAY BLAZAR CANDIDATES IN THE WISH SURVEY AND THEIR RADIO PROPERTIES

According to the second Fermi LAT Catalog (2FGL), about one third of the γ-ray sources listed has no assigned counterpart at lower energies. Many statistical methods have been developed to find the proper counterpart 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 candidates among the unidentified γ-ray sources listed in the 2FGL (UGSs). Combining the WISH and the NVSS radio surveys within the positional uncertainty of the 2FGL UGSs, we select as γ-ray blazar candidates the radio sources characterized by flat radio spectrum between 352 and 1400 MHz. We find 14 new gamma-ray blazar candidates, that could be associated to 8 UGSs and we also discuss on their spectral properties at low radio frequencies. We compare the radio flux density distribution of the low-frequency selected γ-ray blazar candidates with those of the blazar population associated with other methods finding significant differences. Finally, we discuss the results of this association method and its possible applicability to other regions of the sky and future radio surveys