A New Gamma-Ray-emitting Population of FR0 Radio Galaxies

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.