Calculations of the expected TeV $\gamma$-ray emission, produced by accelerated cosmic rays (CRs) in nuclear collisions, from supernova remnants evolving in a uniform interstellar medium (ISM) are presented. The aim is to study the sensitivity of $\gamma$-ray production to a physical parameter set. Apart from its general proportionality to N_H, it is shown that the $\gamma$-ray production essentially depends upon the ratio of the CR diffusion coefficient $\kappa$ to a critical value $\kappa_{ crit}=10(B_0/5 \mu{ G})(N_H/0.3 { cm}^{ -3})^{ -1/3}\kappa_B$, where B_0 and N_H are the magnetic field and hydrogen number density of the ISM, and $\kappa_B$ denotes the Bohm diffusion coefficient. If $\kappa$ is of the same order or lower than $\kappa_{ crit}$, then the peak TeV $\gamma$-ray flux in the Sedov evolutionary phase, normalized to a distance of 1 kpc, is about 10^{ -10}(N_H/0.3 { cm}^{ -3}) photons cm^{ -2} s^{ -1}. For a CR diffusion coefficient that is significantly larger than $\kappa_{ crit}$, the CR cutoff energy is less than 10 TeV and the expected $\gamma$-ray flux at 1 TeV is considerably below the presently detectable level of 10^{ -12} photons cm^{ -2} s^{ -1}. The same is of course true for a SNR in the rarified, so-called hot ISM.
Categories: astro-ph