Three‐dimensional Model of Broadband Emission from Supernova Remnants Undergoing Nonlinear Diffusive Shock Acceleration

Abstract

We present a three-dimensional model of supernova remnants (SNRs) in which the hydrodynamical evolution of the remnant is modeled consistently with nonlinear diffusive shock acceleration occurring at the outer blast wave. The model includes particle escape and diffusion outside of the forward shock and particle interactions with arbitrary distributions of external ambient material, such as molecular clouds. We include synchrotron emission and cooling, bremsstrahlung radiation, neutral pion production, and inverse Compton (IC) and Coulomb energy loss. Broadband spectra have been calculated for typical parameters, including dense regions of gas external to a 1000 yr old SNR. In this paper, we describe the details of our model, but do not attempt a detailed fit to any specific remnant. We also do not include magnetic field amplification (MFA), even though this effect may be important in some young remnants. Our aim is to develop a flexible platform that can be generalized to include effects such as MFA, and that can be easily adapted to various SNR environments, including Type Ia SNRs, which explode in a constant-density medium, and Type II SNRs, which explode in a presupernova wind. When applied to a specific SNR, our model will predict cosmic-ray spectra and multiwavelength morphology in projected images for instruments with varying spatial and spectral resolutions. We show examples of these spectra and images and emphasize the importance of measurements in the hard X-ray, GeV, and TeV gamma-ray bands for investigating key ingredients in the acceleration mechanism, and for deducing whether or not TeV emission is produced by IC from electrons or pion decay from protons.