Multi-frequency study of extragalactic supernova remnants and HII regions

Abstract

We present a multi-frequency study of supernova remnants (SNRs) and $\ion{H}{ii }$ regions in the nearby Sculptor Group Sd galaxy NGC 300, based on new ATCA observations at the wavelengths of 13 and 20 cm, XMM-Newton observations, newly-processed ROSAT (PSPC/HRI; Read & Pietsch 2001) and VLA (20/6 cm) images of this galaxy. We have investigated the physical properties at the X-ray and radio wavelengths of the 28 optical SNRs found by Blair & Long (1997) and have expanded on the multi-wavelength work by Pannuti et al. (2000) on this same galaxy. From a total of 54 radio sources and 11 X-ray sources, we report 18 SNRs and three (3) SNR candidates (classified by spectral index alone) in NGC 300. Five of these 18 SNRs are associated with reported optical SNRs and three have X-ray counterparts. An additional 12 radio SNRs are seen in the Blair & Long (1997) [S II] images. We also investigate the luminosity function of our SNRs. Three background radio sources are confirmed and 12 other sources could represent additional background objects. Twenty two radio correlations with OB associations within NGC 300 correspond to either $\ion{H}{ii }$ regions or SNRs making them a good tracer of SNRs near star-forming regions. Additionally, two radio sources coincide with potential globular clusters of NGC 300 reported by Kim et al. (2002).