A New Gamma-ray Emitting Population of FR0 Radio Galaxies

TL;DR

This paper reports the first detection of gamma-ray emission from FR0 radio galaxies, suggesting they are a significant gamma-ray source and potential contributors to cosmic neutrinos, expanding understanding of their high-energy properties.

Contribution

It provides the first gamma-ray identification of FR0 galaxies and demonstrates their collective gamma-ray emission, highlighting their role in high-energy astrophysics.

Findings

First gamma-ray detection of three FR0 galaxies above 1 GeV.

Detection of cumulative gamma-ray emission from unresolved FR0 sources.

FR0s are likely sources of high-energy neutrinos and cosmic rays.

Abstract

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.