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The new Australian SKA pathfinder (ASKAP) radio telescope is now ramping up towards its full survey mode. In the process, it has conducted several pilot surveys, each of which is a major survey in its own right. Here I will talk about the new results from the EMU Pilot survey, such as the discovery of new giant radio galaxies, and starburst rings in nearby spiral galaxies, and finding that we detect almost all the galaxies in 6dfGS. The biggest surprise was the discovery of a number of circles of radio emission (dubbed Odd Radio Circles) about 1 arcminute in diameter. After discounting the obvious explanations (artefacts, supernova remnants, starburst rings, gravitational lenses, etc) we still have no good explanation of the physical mechanism that is causing them. Our best evidence, from Meerkat and other telescopes, is that they surround galaxies at a redshift of ~0.3, and have a typical diameter of ~1 Mpc, and also show internal structure. The most promising hypothesis is that they result from a spherical shock, perhaps from a cataclysmic event or starburst wind in the central galaxy, but so far we have only circumstantial evidence to support this hypothesis, and so the hunt for an explanation continues. |
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