One of the original motivations for the construction of VERITAS was to search for the origin of the highest energy Galactic cosmic rays. The locations explored in this search include the remnants of historical supernovae, middle-aged supernova remnants interacting with dense molecular clouds, and potential cosmic ray “PeVatrons”, identified by their ultra-high-energy gamma-ray emission. We...
Young massive stellar clusters (YMSCs) have emerged as energetic non-thermal sources, after the recent observation of extended gamma-ray emission by a dozen YMSCs. The large size of their gamma-ray halos, of the order of the excavated bubble from the collective wind, makes the detection of individual YMSCs rather challenging because of the low surface brightness. As a result, the emission from...
Recently, massive-star environments have been established as a new class of gamma-ray sources, which can show degree-scale diffuse emission up to ultra-high energies. They are shaped by feedback from massive stars and harbour a variety of particle accelerators, such as supernova remnants, stellar-wind shocks, and compact objects. A concerted effort of both detailed gamma-ray analyses and...
Cosmic ray acceleration to ~PeV energies has recently emerged as being far more common-place than previously understood. The galactic population of known “ultra high energy” (≥ 100 TeV) gamma-ray emitters encompasses a variety of source classes, including pulsar environments, stellar clusters and dark sources. At these energies, however, cosmic rays may more readily escape their accelerator...
