AMI observations of northern supernova remnants at 14-18 GHz

TL;DR

This study uses the AMI Small Array to observe 12 supernova remnants at 14-18 GHz, providing new high-frequency radio spectra that confirm known features and reveal spectral turnovers and steepening in some remnants.

Contribution

First high-frequency radio observations of several supernova remnants with the AMI SA, improving spectral constraints and confirming spectral features at ~11 GHz.

Findings

Confirmed spectral turnover at ~11 GHz for G74.9+1.2

Detected possible spectral steepening in G54.1+0.3

Identified G84.9+0.5 as an HII region, not an SNR

Abstract

We present observations between 14.2 and 17.9 GHz of 12 reported supernova remnants (SNRs) made with the Arcminute Microkelvin Imager Small Array (AMI SA). In conjunction with data from the literature at lower radio frequencies, we determine spectra of these objects. For well-studied SNRs (Cas A, Tycho's SNR, 3C58 and the Crab Nebula), the results are in good agreement with spectra based on previous results. For the less well-studied remnants the AMI SA observations provide higher-frequency radio observations than previously available, and better constrain their radio spectra. The AMI SA results confirm a spectral turnover at ~11 GHz for the filled-centre remnant G74.9+1.2. We also see a possible steepening of the spectrum of the filled-centre remnant G54.1+0.3 within the AMI SA frequency band compared with lower frequencies. We confirm that G84.9+0.5, which had previously been identified as a SNR, is rather an HII region and has a flat radio spectrum.