2021MNRAS.505.5301R

We carry out 1D hydrodynamical simulations of the evolution of a spherically symmetric supernova remnant (SNR) subject to an external radiation field (ERF) that influences the cooling and heating rates of the gas. We consider homogeneous media with ambient hydrogen number densities n_H, 0_ of 0.1 and 1 cm^–3 permeated by an average radiation field including the cosmic microwave, extragalactic, and Galactic backgrounds, attenuated by an effective column density N_H, eff_ from 10¹⁸ to 10²¹ cm^–2. Our results may be classified into two broad categories: at low N_H, eff_, the ERF presents little absorption in the ultraviolet (ionizing) regime, and all the 'unshielded' cases feature an equilibrium temperature T_eq ∼ 7000 K below which the ambient gas cannot cool further. In this scenario, the SNR develops a nearly isothermal shock profile whose shell becomes thicker over time. At higher N_H, eff_, the ERF is heavily absorbed in the UV range, yielding a roughly constant heating function for temperatures <= 10⁴ K. These 'shielded' cases develop a thin, cold and dense shell throughout their evolution. Energy and momentum injection to the medium do not change significantly between both scenarios, albeit luminosity is higher and more uniformly distributed over the shell for unshielded SNR.