Supernova remnants as cosmic ray accelerators. SNR IC 443

TL;DR

This paper models supernova remnant IC 443 to explore its role as a cosmic ray accelerator and gamma-ray source, emphasizing hydrodynamic interactions with a molecular cloud to explain observed gamma-ray flux.

Contribution

Develops a 3-D hydrodynamical model of SNR IC 443, highlighting the impact of shock-cloud interactions on cosmic ray density and gamma-ray production, aligning with observational data.

Findings

Reverse shock increases cosmic ray density in the interaction region.

Rayleigh-Taylor instability promotes mixing of cosmic rays and cloud material.

Hydrodynamic effects can explain observed gamma-ray flux levels.

Abstract

We examine the hypothesis that some supernova remnants (SNRs) may be responsible for some unidentified gamma-ray sources detected by EGRET instrument aboard the Compton Gamma Ray Observatory. If this is the case, gamma-rays are produced via pion production and decay from direct inelastic collisions of accelerated by SNR shock wave ultrarelativistic protons with target protons of the interstellar medium. We develop a 3-D hydrodynamical model of SNR IC 443 as a possible cosmic gamma-ray source 2EG J0618+2234. The derived parameters of IC 443: the explosion energy E_o=2.7*10^{50} erg, the initial hydrogen number density n(0)=0.21 cm^{-3}, the mean radius R=9.6 pc and the age t=4500 yr result in too low gamma-ray flux, mainly because of the low explosion energy. Therefore, we investigate in detail the hydrodynamics of IC 443 interaction with a nearby massive molecular cloud and show that the reverse shock wave considerably increases the cosmic ray density in the interaction region. Meantime, the Rayleigh-Taylor instability of contact discontinuity between the SNR and the cloud provides an effective mixing of the containing cosmic ray plasma and the cloud material. We show that the resulting gamma-ray flux is consistent with the observational data.