A systematic comparison of ionization temperatures between ionizing and recombining plasmas in supernova remnants

Shigeo Yamauchi, Masayoshi Nobukawa, Katsuji Koyama

Published 2021-04-06Version 1

The temperatures of the plasma in the supernova remnants (SNRs) are initially very low just after the shock heating. The electron temperature (kT_{e}) increases quickly by Coulomb interaction, and then the energetic electrons gradually ionize atoms to increase the ionization temperature (kT_{i}). The observational fact is that most of the young and middle-to-old aged SNRs have lower kT_{i} than kT_{e} after the shock heating. The temperature evolution in the shell-like SNRs has been explained by this ionizing plasma (IP) scenario. On the other hand, in the last decade, a significant fraction of the mixed morphology SNRs was found to exhibit a recombining plasma (RP) with higher kT_{i} than kT_{e}. The origin and the evolution mechanism of the RP SNRs have been puzzling. To address this puzzle, this paper presents the kT_{e} and kT_{i} profiles using the observed results by follow-up Suzaku observations, and then proposes a new scenario for the temperature and morphology evolutions in the IP and RP SNRs.