A Study of Optical Observing Techniques for Extra-Galactic Supernova Remnants: Case of NGC 300

TL;DR

This study evaluates optical techniques for identifying extragalactic supernova remnants in NGC 300, highlighting the limitations of spectral line ratios and the need for high-resolution imaging for accurate confirmation.

Contribution

It investigates the reliability of the [Sii]/Halpha > 0.4 criterion and assesses the effectiveness of observational techniques in extragalactic SNR surveys.

Findings

Spectral line ratio criterion may be unreliable for SNR identification.

High-resolution imaging is often necessary for confirmation.

Spectroscopic techniques can be hampered by seeing conditions and pointing errors.

Abstract

We present the results of a study of observational and identification techniques used for surveys and spectroscopy of candidate supernova remnants (SNRs) in the Sculptor Group galaxy NGC 300. The goal of this study was to investigate the reliability of using [Sii]/Halpha > 0.4 in optical SNR surveys and spectra as an identifying feature of extra-galactic SNRs (egSNRs) and also to investigate the effectiveness of the observing techniques (which are hampered by seeing conditions and telescope pointing errors) using this criterion in egSNR surveys and spectrographs. This study is based on original observations of these objects and archival data obtained from the Hubble Space Telescope which contained images of some of the candidate SNRs in NGC 300. We found that the reliability of spectral techniques may be questionable and very high-resolution images may be needed to confirm a valid identification of some egSNRs.