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

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.