Observation of gamma rays up to 320 TeV from the middle-aged TeV pulsar wind nebula HESS J1849-000

Amenomori, Michihiro*; Tsuchiya, Harufumi ; Tibet AS Collaboration*; 116 of others*

Gamma rays from HESS J1849-000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays reaches and levels above 25 TeV and 100 TeV, respectively. The energy spectrum measured between 40 TeV E 320 TeV for the first time is described with a simple power-law function of dN/dE = . The gamma-ray energy spectrum from the sub-TeV to sub-PeV ranges including the results of previous studies can be modeled with the leptonic scenario, Inverse Compton Scattering by high-energy electrons accelerated by the PWN of PSR J1849-0001, but the scenario requires sophisticated theoretical modeling. On the other hand, the gamma-ray energy spectrum can be simply modeled with the hadronic scenario in which gamma rays are generated from the decay of neutral pions produced by collisions between accelerated cosmic-ray protons and the ambient molecular cloud found in the gamma-ray emitting region. The cutoff energy of cosmic-ray protons is estimated at , suggesting that protons are accelerated up to the PeV energy range. Our study proposes that HESS J1849-000 should be further investigated as a new candidate for a Galactic PeV cosmic-ray accelerator, or "PeVatron".