2022A&A...660A...8B

The recent measurement by LHAASO of gamma-ray emission extending up to hundreds of TeV from multiple Galactic sources represents a major observational step forward in the search for the origin of the Galactic cosmic rays. The burning question is if this ultra-high-energy emission is associated with the acceleration of protons and/or nuclei to PeV energies, or if it can be associated with PeV-electron accelerators. A strong Klein-Nishina suppression of inverse Compton emission at these energies is unavoidable; nevertheless, we show here that inverse Compton emission can provide a natural explanation for the measured emission and that an association with the established PeV-electron accelerating source class of pulsar wind nebulae is also rather natural. However, a clear distinction between different models requires taking multi-wavelength data into account, having good knowledge of the local environmental conditions, and, in some cases, performing multi-source modelling.