Re-identification of G35.6-0.4 as a supernova remnant

TL;DR

This study reclassifies G35.6-0.4 as a supernova remnant based on new radio observations, spectral analysis, and lack of infrared emission, clarifying its nature in the Galactic plane.

Contribution

The paper provides the first detailed extent measurement and spectral analysis confirming G35.6-0.4 as a supernova remnant rather than an HII region.

Findings

G35.6-0.4 has a non-thermal spectral index of -0.47 +/- 0.07.

The source shows partial limb brightening.

It lacks associated infrared emission.

Abstract

G35.6-0.4 is an extended radio source in the Galactic plane which has previously been identified as either a supernova remnant or an HII region. Observations from the VLA Galactic Plane Survey at 1.4 GHz with a resolution of 1 arcmin allow the extent of G35.6-0.4 to be defined for the first time. Comparison with other radio survey observations show that this source has a non-thermal spectral index, with alpha -0.47 +/- 0.07. G35.6-0.4 does not have obvious associated infra-red emission, so it is identified as a Galactic supernova remnant, not an HII region. It is approximately 15 x 11 arcmin**2 in extent, showing partial limb brightening.