Thermal X-ray emission from shocked ejecta in Type Ia supernova remnants. II. Parameters affecting the spectrum

The supernova remnants (SNRs) left behind by Type Ia supernovae (SNe) provide an excellent opportunity for the study of these enigmatic objects. In a previous work we showed that it is possible to use the X-ray spectra of young Type Ia SNRs to explore the physics of Type Ia SNe and identify the relevant mechanism underlying these explosions. Our simulation technique is based on hydrodynamic and nonequilibrium ionization calculations of the interaction of a grid of Type Ia explosion models with the surrounding ambient medium, coupled to an X-ray spectral code. In this work we explore the influence of two key parameters on the shape of the X-ray spectrum of the ejecta: the density of the ambient medium around the SN progenitor and the efficiency of collisionless electron heating at the reverse shock. We also discuss the performance of recent three-dimensional simulations of Type Ia SN explosions in the context of the X-ray spectra of young SNRs. We find a better agreement with the observations for Type Ia SN models with stratified ejecta than for three-dimensional deflagration models with well-mixed ejecta. We conclude that our grid of Type Ia SNR models can improve our understanding of these objects and their relationship to the SNe that originated them.