Radio-continuum study of the nearby Sculptor group Galaxies. Part 2: NGC 55 at λ=20, 13, 6 and 3 cm

Abstract

A series of new radio-continuum (λ=20, 13, 6 and 3 cm) mosaic images focused on the NGC 55 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 μJy) 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 H ii regions and 6 as supernova remnant candidates. This relatively low number of SNR candidates detected coupled with the low number of large H ii regions is consistent with the estimated low star formation rate of the galaxy at 0.06 M ⊙ year−1. Our spectral index map shows that the core of galaxy appears to have a shallow spectral index between α=−0.2 and −0.4. This indicates that the core of the galaxy is a region of high thermal radiation output.