Tracing the sources of cosmic rays with molecular ions

TL;DR

This paper predicts that supernova remnants significantly increase ionization rates in interstellar gas, leading to detectable molecular ion emissions that can confirm their role as cosmic ray sources.

Contribution

It provides the first quantitative calculation linking supernova remnants to elevated cosmic ray ionization and predicts observable molecular ion emission lines for the first time.

Findings

Ionization rates near supernova remnants are much higher than the Galactic average.

H_{2}^{+} and H_3^+ emission lines are predicted to be detectable.

Coincident detection of these lines with gamma-rays can confirm supernova remnants as cosmic ray sources.

Abstract

The rate of ionization by cosmic rays in interstellar gas directly associated with gamma-ray emitting supernova remnants is for the first time calculated to be several orders of magnitude larger than the Galactic average. Analysis of ionization-induced chemistry yields the first quantitative prediction of the astrophysical H_{2}^{+} emission line spectrum, which should be detectable together with H_3^+ lines. The predicted coincident observation of those emission lines and gamma-rays will help prove that supernova remnants are sources of cosmic rays.