Diffuse gamma-ray emissions around the stellar cluster Berkeley 59

Abstract We report a detailed analysis on the young stellar cluster Berkeley 59 using Fermi-LAT. Using up-to-date source catalog and background models, we found significant extended GeV emission around Berkeley 59, which can be modeled by a radial Gaussian of 1.02○ radius with a significance of the extension of 10.6σ. We investigated the molecular, neutral and ionized gas content and the hadronic origin. The gamma-ray spectrum of Berkeley 59 has a photon index of 2.88 ± 0.06. The derived gas mass from H2, HI and HII around Berkeley 59 is ∼6.34 × 104M⊙. We derived the relationship between cosmic ray acceleration efficiency and diffusion coefficient. Our results suggest that the extended gamma-ray emission originates from cosmic rays accelerated by cluster winds interacting with surrounding gas.