Newly confirmed and candidate Galactic SNRs uncovered from the AAO/UKST Hα survey

We present a catalogue of 18 new Galactic supernova remnants (SNRs) uncovered in the optical regime as filamentary emissions and extended nebulosities on images of the Anglo-Australian Observatory/United Kingdom Schmidt Telescope (AAO/UKST) Hα survey of the southern Galactic plane. Our follow-up spectral observations confirmed classical optical SNR emission lines for these 18 structures via detection of very strong [S ii] at 6717 and 6731 Ņ relative to Hα ([S ii]/Hα > 0.5). Morphologically, 10 of these remnants have coherent, extended arc or shell structures, while the remaining objects are more irregular in form but clearly filamentary in nature, typical of optically detected SNRs. In 11 cases there was a clear if not complete match between the optical and radio structures with Hα filamentary structures registered inside and along the presumed radio borders. Additionally, ROSAT X-ray sources were detected inside the optical/radio borders of 11 of these new remnants and three may have an associated pulsar. The multiwavelength imaging data and spectroscopy together present strong evidence to confirm identification of 18 new, mostly senile Galactic SNRs. This includes G288.7-6.3, G315.1+2.7 and G332.5-5.6, identified only as possible remnants from preliminary radio observations. We also confirm existence of radio-quiet but optically active SNRs.