ASKAP-EMU Discovery of New Galactic SNR Candidate: Unicycle (G312.65+2.87)

Abstract

We present the serendipitous discovery of a low surface brightness Galactic supernova remnant candidate, Unicycle (G312.65+2.87). Unicycle was initially discovered in the Evolutionary Map of the Universe large-scale radio survey at 943.5 MHz. We measure a diffuse shell (D = 288″ × 300″) and an integrated flux density of S I 944 MHz = 150 ± 20 mJy. We estimate the most likely intrinsic diameters of 30 < D < 36 pc or 42 < D < 47 pc, corresponding to distances of 10 < d < 12 kpc or 14 < d < 16 kpc, placing it within either the Scutum–Centaurus or outer Sagittarius spiral arms.