Acceleration of cosmic rays at supernova remnant shocks: constraints from gamma-ray observations

TL;DR

Gamma-ray observations of supernova remnants provide crucial insights into cosmic ray acceleration, but definitive proof remains elusive due to challenges in distinguishing emission sources.

Contribution

This paper reviews recent gamma-ray observations of supernova remnants and discusses their implications for understanding cosmic ray acceleration.

Findings

Detection of gamma-ray emission from shell-type supernova remnants.

Challenges in differentiating hadronic and leptonic gamma-ray contributions.

Gamma-ray observations support but do not conclusively prove supernova remnants accelerate cosmic rays.

Abstract

In the past few years, gamma-ray astronomy has entered a golden age. At TeV energies, only a handful of sources were known a decade ago, but the current generation of ground-based imaging atmospheric Cherenkov telescopes has increased this number to more than one hundred. At GeV energies, the Fermi Gamma-ray Space Telescope has increased the number of known sources by nearly an order of magnitude in its first 2 years of operation. The recent detection and unprecedented morphological studies of gamma-ray emission from shell-type supernova remnants is of great interest, as these analyses are directly linked to the long standing issue of the origin of the cosmic-rays. However, these detections still do not constitute a conclusive proof that supernova remnants accelerate the bulk of Galactic cosmic-rays, mainly due to the difficulty of disentangling the hadronic and leptonic contributions to the observed gamma-ray emission. In this talk, I will review the most relevant cosmic ray related results of gamma ray astronomy concerning supernova remnants.