Radio-Continuum Study of the Nearby Sculptor Group Galaxies. Part 2: NGC 55 at {\lambda}=20, 13, 6 and 3 cm

TL;DR

This study produced high-resolution, sensitive radio-continuum images of NGC 55 at multiple wavelengths, identifying new sources and analyzing the galaxy's star formation activity and core properties.

Contribution

The paper presents new, high-resolution radio images of NGC 55 at four wavelengths, identifying 66 new sources and providing insights into the galaxy's star formation rate and core emission characteristics.

Findings

Identified 66 new discrete radio sources in NGC 55.

Detected a low number of supernova remnant candidates, consistent with low star formation rate.

Core region shows a shallow spectral index indicating high thermal radiation output.

Abstract

A series of new radio-continuum ({\lambda}=20, 13, 6 and 3 cm) mosaic images focused on the NGC55 galactic system were produced using archived observational data from the Australia Telescope Compact Array. These new images are both very sensitive (down to rms=33 {\mu}Jy) and feature high angular resolution (down to <4"). Using these newly created images, 66 previously unidentified discrete sources are identified. Of these sources, 46 were classified as background sources, 11 as HII regions and 6 as supernova remnant candidates. This relatively low number of SNR candidates detected coupled with the low number of large HII regions is consistent with the estimated low star formation rate of the galaxy at 0.06 solar masses per year. Our spectral index map shows that the core of galaxy appears to have a shallow spectral index between {\alpha} = -0.2 and -0.4. This indicates that the core of the galaxy is a region of high thermal radiation output.