Hopkins et al.describe the Evolutionary Map of the Universe (EMU) survey being conducted with ASKAP. EMU aims to deliver the touchstone radio atlas of the southern hemisphere. The paper introduces EMU and reviews its science drivers and key science goals. The development of the survey strategy and planned sky coverage is presented, along with the operational aspects of the survey and associated data analysis, together with a selection of diagnostics demonstrating the imaging quality and data characteristics.

It is expected that EMU will reveal sources that were rare enough, or faint enough, that they would not have been found in previous surveys. Many extended or unusually-shaped radio sources can be explained by “weather”, i.e., variations in the jets or winds or inhomogeneities in the surrounding medium. There are a small subset, though, which go beyond this. This subset contains sources that appear inconsistent with our current physical models, and have the potential to allow genuinely new insight into the associated astrophysical processes. The images above are examples of unusual sources found in EMU. Each represents examples of physical processes that differ from current models. (a) Potentially interacting spiral galaxies; insets drawn from the DESI (Dark Energy Spectroscopic Instrument) Legacy Survey. (b) Diffuse radio emission (shown in purple) overlaid on a DESI Legacy Survey image. (c) EMU ∼15 arcsecond radio image in grey, overlaid with 8 arcsecond image in blue. (d) A single contour from the diffuse image at 10 µJy per 15 arcsecond beam, outlining the location of very low brightness diffuse radio emission, overlaid on the DESI Legacy Survey image.