Investigating Galactic cosmic rays with <i>γ</i>-ray astronomy

Abstract

Cosmic rays (CRs) are one of the most important components in the interstellar medium (ISM), and the origin of CRs remains a mystery. The diffusion of CRs in turbulent magnetic fields erases the information on the distribution of CR accelerators to a large extent. The energy dependent diffusion of CRs also significantly modifies the initial (acceleration) spectra of CRs. In this regard, <i>γ</i>-rays, the secondary products of interactions of CRs with gas and photons in the ISM, provide us with more information about the origin of CRs. More specifically, the <i>γ</i>-ray emissions associated with gas, can be used to study the distribution of CRs throughout the Galaxy; discrete <i>γ</i>-ray sources can elucidate the locations of individual CR accelerators. Here, the current status and prospects in these fields are reviewed.