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1st of September 2023
ASKAP discovery of candidate supernova remnants
by Ball et al.
Ball et al. have used data from the pilot observations of the EMU/POSSUM surveys to study the "missing supernova remnant (SNR) problem" -- the discrepancy between the number of Galactic SNRs that have been observed and the number that are estimated to exist. In a pilot survey field containing the plane of our Galaxy, the team found 7 known SNRs and 21 SNR candidates, of which 13 have not been previously studied. The image above shows 933 MHz images of three of the new SNR candidates, with Galactic longitude on the x-axis and Galactic latitude on the y-axis. G324.3+0.2 (left) has a shell structure that is almost perfectly circular, with some brightening towards the southeast. Based on the distinct morphology and clear lack of an MIR counterpart, this is a strong candidate for classification as an SNR. A large, bright HII region can be seen to the right (west) of the source. G324.4−0.4 (centre) is an elliptical shell with brightening along the southwest edge. There are many overlapping point sources and a couple of known HII regions located to the northeast. There is overlapping emission in the MIR but nothing that clearly mirrors the shell structure seen in the radio. G324.4−0.2 (right) is a very small, faint shell-like structure with an overlapping point source. It is located just north of G324.4−0.4 and can also be seen in the central image. There is no obvious MIR counterpart, supporting the identification as an SNR. The results of this paper demonstrate the potential of the full EMU/POSSUM surveys to uncover more of the missing Galactic SNR population.

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