Evolution of High-energy Particle Distribution in Supernova Remnants

TL;DR

This study updates spectral fits for supernova remnants and analyzes gamma-ray spectra, revealing that most SNRs with soft TeV spectra can be modeled with a single power-law ion distribution, impacting our understanding of cosmic ray origins.

Contribution

It provides new spectral analysis of SNRs and suggests that SNRs in star-burst galaxies may not produce soft gamma-ray spectra, challenging existing cosmic ray models.

Findings

17 out of 20 SNRs fit a single power-law ion distribution with index ~2.6

SNRs in star-burst galaxies may not reach the soft gamma-ray spectrum phase

Implication that SNRs' contribution to Galactic cosmic rays is limited by their spectral evolution

Abstract

The spectra fits to a sample of 34 supernova remnants (Zeng et al., 2019) are updated. $\gamma$-ray spectra of 20 supernova remnants (SNRs) with a soft TeV spectrum are further analyzed. We found that 17 of them can be fitted in the hadronic scenario with a single power-law ion distribution with an index of $\sim$ 2.6, which is significantly softer than the ion distribution inferred from $\gamma$-ray observations of star-burst galaxies. If Galactic cosmic rays are mostly produced by SNRs, this result suggests that SNRs in star-burst galaxies may never reach the phase with a soft $\gamma$-ray spectra or escape of high-energy particles from SNRs before they reach this phase with a soft $\gamma$-ray spectrum dominates the contribution of SNRs to Galactic cosmic rays.