Identifying the Gamma-Ray Emission of the Nearby Galaxy M83

Abstract

We report on the detection of a γ-ray source at the position of the nearby star-forming galaxy (SFG) M83, which is found from our analysis of 14 yr of the data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi). The source is weakly detected, with a significance of ∼5σ, and its emission can be described with an exponentially cutoff power law. At a distance of 4.61 Mpc, the source’s γ-ray luminosity is ∼1.4 × 1039 erg s−1, roughly along the correlation line between the γ-ray and IR luminosities determined for nearby SFGs. Because of the weak detection, the source spectrum can not be used for checking its similarity with those of other SFGs. Given the positional matches and the empirical expectation for γ-ray emission from M83 due to the galaxy’s star-forming activity, we conclude that the γ-ray source is the likely counterpart to M83. The detection thus adds another member to the group of approximately a dozen SFGs, whose γ-ray emissions mostly have a cosmic-ray origin.