The Most Likely Sources of High Energy Cosmic-Ray Electrons in Supernova Remnants

Abstract

Evidences of non-thermal X-ray emission and TeV gamma-rays from the supernova remnants (SNRs) has strengthened the hypothesis that primary Galactic cosmic-ray electrons are accelerated in SNRs. High energy electrons lose energy via synchrotron and inverse Compton processes during propagation in the Galaxy. Due to these radiative losses, TeV electrons liberated from SNRs at distances larger than ~1 kpc, or times older than ~10^5 yr, cannot reach the solar system. We investigated the cosmic-ray electron spectrum observed in the solar system using an analytical method, and considered several candidate sources among nearby SNRs which may contribute to the high energy electron flux. Especially, we discuss the effects for the release time from SNRs after the explosion, as well as the deviation of a source spectrum from a simple power-law. From this calculation, we found that some nearby sources such as the Vela, Cygnus Loop, or Monogem could leave unique signatures in the form of identifiable structure in the energy spectrum of TeV electrons and show anisotropies towards the sources, depending on when the electrons are liberated from the remnant. This suggests that, in addition to providing information on the mechanisms of acceleration and propagation of cosmic-rays, specific cosmic-ray sources can be identified through the precise electron observation in the TeV region.