Correlation of Supernova Remnant Masers and Gamma-Ray Sources

TL;DR

This study demonstrates a correlation between supernova remnant masers and gamma-ray sources, indicating enhanced cosmic ray densities and ionization rates in these interacting systems, which support cosmic ray acceleration and chemistry in post-shock gas.

Contribution

It provides the first statistical evidence linking supernova remnant masers with gamma-ray sources, revealing elevated cosmic ray densities in these environments.

Findings

Cosmic ray density is 10-100 times higher than local values.

Enhanced ionization rates explain observed non-equilibrium chemistry.

Correlation supports supernova remnants as cosmic ray accelerators.

Abstract

Supernova remnants interacting with molecular clouds are potentially exciting systems in which to detect evidence of cosmic ray acceleration. Prominent gamma-ray emission is produced via the decay of neutral pions when cosmic rays encounter the nearby dense clouds. In many of the supernova remnants coincident with gamma-ray sources, the presence of OH(1720 MHz) masers is used to identify interaction with dense gas and to provide a kinematic distance to the system. In this paper we use statistical tests to demonstrate that there is a correlation between these masers and a class of GeV- to TeV-energy gamma-ray sources coincident with interacting remnants. For pion decay, the gamma-ray luminosity provides a direct estimate of the local cosmic ray density. We find the cosmic ray density is enhanced by one to two orders of magnitude over the local solar value, comparable to X-ray-induced ionization in these remnants. The inferred ionization rates are sufficient to explain non-equilibrium chemistry in the post-shock gas, where high columns of hydroxyl are observed.