Cosmic Ray PeVatrons in the Milky Way

Abstract: We are witnessing spectacular discoveries of ultra-high energy (UHE; E > 100 TeV) gamma-ray sources in the Milky Way, revealing the sites of PeVatrons - Cosmic Ray Factories accelerating protons and electrons beyond 1 PeV. These perfectly designed particle accelerators represent at least three galactic source populations - pulsars, microquasars, and stellar clusters. On the other hand, we do not yet have direct evidence of UHE gamma rays from young Supernova Remnants. For decades, this source population was considered responsible for the locally measured Cosmic Rat flux up to the so-called “knee” at a few PeV. However, we cannot rule out that some unidentified UHE gamma-ray sources are associated with giant molecular clouds in the vicinity of middle-aged supernova remnants. I will discuss the implications of these exciting and, in many cases, unexpected discoveries for the long-standing puzzle of the origin of Galactic Cosmic Rays.

Rome Joint Astrophysics Colloquium