Infrared and X-ray emission of a supernova remnant in a clumpy medium

Abstract

The infrared (IR) to X-ray luminosity ratio (IRX) is an indicator of the role of the dust plays in cooling of hot gas in supernova remnants (SNR). Using the 3D dynamics of gas and interstellar polydisperse dust grains we analyze the evolution of SNR in the inhomogeneous medium. We obtain spatial distributions of the surface brigthness both of the X-ray emission from hot gas inside SNR and the IR emission from the SNR swept-up shell, as well as, the average gas temperature in the SNR, $T_X$. We find that the IRX changes significantly (by a factor of $\sim 3-30$) as a function of impact distance within the SNR and its age. In a low inhomogeneous medium the IRX drops rapidly during the SNR evolution. On the other hand, if large inhomogeneities are present in the medium, the IRX is maintained at higher levels during the late SNR evolution at radiative phase due to replenishment of dust in the hot gas by incompletely destroyed fragments behind the shock front. We show that the onset of the radiative phase determines the evolution of the $T_X - {\rm IRX}$ diagram. We illustrate that decreasing gas metallicity or density leads to high values of temperature and IRX ratio. We discuss how our results can be applied to the observational data to analyse the SNR older than 10 kyr (i.e. when the mass of the swept-up dust in the shell is expected to exceed that produced in the SNR) in the Galaxy and Large Magellanic Cloud.