Contribution of young massive stellar clusters to the Galactic diffuse neutrino and gamma-ray emissions

Young massive stellar clusters (YMSCs) have emerged as energetic non-thermal sources, after the recent observation of extended 𝛾-ray emission by a dozen YMSCs. The large size of their gamma-ray halos, of the order of the excavated bubble from the collective wind, makes the detection of individual YMSCs rather challenging because of the low surface brightness. As a result, the emission from most of the Galactic YMSCs could be unresolved, thus contributing to the diffuse 𝛾-ray radiation and neutrino flux observed along the Galactic Plane. In this study, we estimate that possible contribution of the population of YMSCs to the Galactic diffuse radiative emissions, by simulating synthetic samples of these sources resembling the observed properties of local clusters. We compute the resulting secondary emission from hadronic interactions occurring in each cluster by particles accelerated at the cluster’s collective wind termination shock and at the supernovae exploded in the core, and compare them with available diffuse 𝛾-ray and neutrino observations by different experiments, including ARGO, LHAASO, and IceCube.