  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 gamma-ray identification of three FR0
galaxies above 1 GeV using more than a decade of the Fermi Large Area Telescope
observations. A cumulative gamma-ray emission at >5 sigma significance was also
detected from the gamma-ray unresolved FR0 sources using the stacking
technique, suggesting the FR0 population to be a gamma-ray emitter as a whole.
The multi-frequency properties of the gamma-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 gamma-ray
production mechanism and the origin of cosmic neutrinos.
