2021ApJ...918L..39P

The enigmatic class of Fanaroff-Riley type 0 (FR0) radio galaxies is emerging as the missing link between the faint yet numerous population of compact radio sources in nearby galaxies and the canonical Fanaroff-Riley classification scheme. This Letter reports the first γ-ray identification of three FR0 galaxies above 1 GeV using more than a decade of the Fermi Large Area Telescope observations. A cumulative γ-ray emission at >5σ significance was also detected from the γ-ray unresolved FR0 sources using the stacking technique, suggesting the FR0 population to be a γ-ray emitter as a whole. The multifrequency properties of the γ-ray-detected sources are similar to other FR0s, thus indicating the high-energy radiation to originate from misaligned jets. Given their large abundance, FR0 radio galaxies are proposed as plausible candidates for IceCube-detected neutrinos and the results presented in this Letter may provide crucial constraints on their γ-ray production mechanism and the origin of cosmic neutrinos.