A 95 GHz Methanol Emission Survey Toward Eight Small Supernova Remnants

TL;DR

This study conducted a 95 GHz methanol emission survey of eight small supernova remnants, detecting emission in three near the Galactic center, and analyzed the excitation mechanisms involved.

Contribution

First survey of 95 GHz methanol emission in small SNRs, revealing spatial peaks and suggesting excitation by SNR interaction and molecular gas in the CMZ.

Findings

Methanol emission detected in 3 SNRs near the Galactic center.

Emission mainly surrounds SNRs and shows nine spatial peaks.

Excitation likely caused by SNR interaction and molecular gas, not tidal forces.

Abstract

We report on a 95 GHz ($8_0-7_1$ A$^{+}$) methanol (CH$_3$OH) emission survey with the Purple Mountain Observatory Delingha 13.7 m telescope. Eight supernova remnants (SNRs) with angular size $\lesssim$ 10' were observed, but emission was only detected in three SNRs near the Galactic center (Sgr A East, G 0.1-0.1, and G 359.92-0.09). CH$_3$OH emission mainly surrounds the SNRs and can be decomposed into nine spatial peaks with velocity range of eight peaks being (-30, 70) km s$^{-1}$, and the other (70, 120) km s$^{-1}$. They are probably excited by interaction with these SNRs and adjacent molecular gas in the central molecular zone (CMZ), although star formation may play an important role in exciting CH$_3$OH emission in some regions of CMZ. We infer that tidal action is unlikely to be an excitation source for CH$_3$OH emission.