Diffuse GeV emission in the field of HESS J1912+101 revisited

Abstract

We have analyzed 12 years of Fermi Large Area Telescope data toward the HESS J1912+101 region. With the latest source catalog and diffuse background models, a γ-ray excess is detected with a significance of ~8σ in the energy range of above 10 GeV. It has been argued that the diffuse GeV emission in the vicinity of HESS J1912+101 are from an extended pulsar wind nebula powered by PSR J1913+1011 and also that the hard GeV emission above 10 GeV stems from the shell-type supernova remnant and is connected with the TeV emissions. Different from previous works, our analysis indicates that the H2 spatial template is preferred over the other spatial templates, suggesting that the diffuse emission component spatially correlates with the dense molecular gas. This spatial correlation favors a hadronic emission scenario, although a leptonic origin cannot be ruled out. In the hadronic scenario, the parent proton spectrum can be described by a power-law function with an index of α = 2.36 ± 0.16. Above 50 GeV, there is no emission, and the upper limits reveal a spectral cutoff or break in the parent proton spectrum that can be explained as propagation effects of cosmic rays. We argue that the parent protons may come from the candidate supernova remnant HESS J1912+101 or the young massive star cluster Mc20.