Non-equilibrium ionisation and radiative transport in an evolving supernova remnant

Abstract: We present numerical simulations of the evolution of a supernova (SN) remnant expanding into a uniform background medium with density $n_H = 1.0$ cm$^{-3}$ and temperature of $10^4$ K. We include a dynamically evolving non-equilibrium ionisation (NEI) network (consisting of all the ions of H, He, C, N, O, Ne, Mg, Si, S, Fe), frequency dependent radiation transfer (RT), thermal conduction, and a simple dust evolution model, all intra-coupled to each other and to the hydrodynamics. We assume spherical symmetry. Photo-ionisation, radiation losses, photo-heating, charge-exchange heating/cooling and radiation pressure are calculated on-the-fly depending on the local radiation field and ion fractions. We find that the dynamics and energetics (but not the emission spectra) of the SN remnants can be well modelled by collisional equilibrium cooling curves even in the absence of non-equilibrium cooling and radiative transport. We find that the effect of precursor ionising radiation at different stages of SN remnant are dominated by rapid cooling of the shock and differ from steady state shocks. The predicted column densities of different ions such as N II, C IV and N V, can be higher by up to several orders of magnitude compared to steady state shocks. We also present some high esolution emission spectra that can be compared with the observed remnants to obtain important information about the physical and chemical states of the remnant, as well as constrain the background ISM.