This book presents two candidates for astrophysical accelerators of cosmic rays with petaelectron-volt (PeV) energies in our Galaxy, the so-called PeVatrons, through the observation of sub-PeV gamma rays performed by the Tibet air shower array. The two gamma-ray sources are TASG J1844-038—a newly detected source in this presented work—and HESS J1849-000. Reconstructing their gamma-ray energy spectra up to the sub-PeV range and also analyzing the archive data published by a radio survey, the book discusses in depth the emission mechanisms of the observed gamma rays and suggests that...