Hadronic gamma-ray images of Sedov supernova remnants

Abstract

A number of modern experiments in high-energy astrophysics produce images of supernova remnants (SNRs) in the TeV and GeV gamma-rays. Either relativistic electrons (due to the inverse-Compton scattering) or protons (due to the pion decays) may be responsible for this emission. In particular, the broad-band spectra of SNRs may be explained in both leptonic and hadronic scenarios. Another kind of observational data, namely, images of SNRs, is an important part of experimental information. We present a method to model gamma-ray images of Sedov SNRs in uniform media and magnetic field due to hadronic emission. These gamma-rays are assumed to appear as a consequence of meson decays produced in inelastic collisions of accelerated protons with thermal protons downstream of the shock - a model would be relevant for SNRs without firm confirmations of the shock-cloud interaction, as e.g. SN1006. Distribution of surface brightness of the shell-like SNR is synthesized numerically for a number of configurations. An approximate analytical formula for azimuthal and radial variation of hadronic gamma-ray brightness close to the shock is derived. The properties of images as well as the main factors determining the surface brightness distribution are determined. Some conclusions which would be relevant to SN1006 are discussed.Comment: 11 pages, 7 figures, to be published in MNRA