Discovery of New Interacting Supernova Remnants in the Inner Galaxy

TL;DR

This study used radio telescopes to discover four new supernova remnants interacting with molecular clouds via OH masers, revealing their distribution in the Galaxy and suggesting many such remnants remain undetected.

Contribution

The paper reports the discovery of four new interacting supernova remnants with OH masers, expanding the known sample and highlighting their distribution and detection limitations.

Findings

Four new interacting SNRs with OH masers detected

Maser-emitting SNRs are concentrated within 50° Galactic longitude

Many SNR masers likely remain undetected due to survey sensitivity limits

Abstract

OH(1720 MHz) masers are excellent signposts of interaction between supernova remnants(SNRs) and molecular clouds. Using the GBT and VLA we have surveyed 75 SNRs and six candidates for maser emission. Four new interacting SNRs are detected with OH masers: G5.4-1.2, G5.7-0.0, G8.7-0.1 and G9.7-0.0. The newly detected interacting SNRs G5.7-0.0 and G8.7-0.1 have TeV gamma-ray counterparts which may indicate a local cosmic ray enhancement. It has been noted that maser-emitting SNRs are preferentially distributed in the Molecular Ring and Nuclear Disk. We use the present and existing surveys to demonstrate that masers are strongly confined to within 50 degrees Galactic longitude at a rate of 15 percent of the total SNR population. All new detections are within 10 degrees Galactic longitude emphasizing this trend. Additionally, a substantial number of SNR masers have peak fluxes at or below the detection threshold of existing surveys. This calls into question whether maser surveys of Galactic SNRs can be considered complete and how many maser-emitting remnants remain to be detected in the Galaxy.