Gamma-ray emission from crushed clouds in supernova remnants

Abstract

It is shown that the radio and gamma-ray emission observed from newly found "GeV-bright" supernova remnants (SNRs) can be explained by a model in which a shocked cloud and shock-accelerated cosmic rays (CRs) frozen in it are simultaneously compressed by the supernova blast wave as a result of formation of a radiative cloud shock. Simple reacceleration of pre-existing CRs is generally sufficient to power the observed gamma-ray emission through the decays of π0-mesons produced in hadronic interactions between high-energy protons (nuclei) and gas in the compressed-cloud layer. This model provides a natural account of the observed synchrotron radiation in SNRs W51C,W44, and IC 443 with flat radio spectral index, which can be ascribed to a combination of secondary and reaccelerated electrons and positrons. © 2010. The American Astronomical Society. All rights reserved.