Lepto-hadronic origin of γ-rays from the G54.1+0.3 pulsar wind nebula

Abstract

Abstract G54.1+0.3 is a Crab-like pulsar wind nebula (PWN) with the highest γ-ray to X-ray luminosity ratio among all the nebulae driven by young rotation-powered pulsars. We model the spectral evolution of the PWN and find it difficult to match the observed multiband data with leptons alone using reasonable model parameters. In a lepton–hadron hybrid model, however, TeV photons come mainly from π0 decay in proton–proton interaction and the observed photon spectrum can be well reproduced. The newly discovered infrared loop and molecular cloud that lie in or closely around the PWN can work as the target for the bombardment of the PWN protons.