Norris et al. present a catalogue of 3557 Double Radio sources associated with Active Galactic Nuclei (DRAGNs) from the First Pilot Survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with ASKAP covering 270 square degrees. The catalogue will be used to explore the properties of these sources, to train machine-learning algorithms for the detection of these sources in larger fields, and to compare with the results of Citizen Science projects, with the ultimate goal of understanding the physical processes that drive DRAGNs. Compared with earlier, lower sensitivity, catalogues, the team find more diffuse structure and a plethora of more complex structures, ranging from wings of radio emission on the side of the jets, to types of object which have not been seen in earlier observations.

The majority of sources can be classified into two morphological types: Fanaroff-Riley Class I (FR1) and Fanaroff-Riley Class II (FR2), according to the position of the brightness peaks of the radio emission. FR1 sources are edge-dimmed, and appear to gradually decelerate along their length. Conversely, FR2 sources are edge-brightened and seem to remain relativistic along their length until they abruptly end in a hotspot. Classifying a source as FR1 or FR2 relies on the measurement of “a”, the distance between the peaks, and “b”, the total extent of the source. FR1 have a/b < 0.5 and FR2 have a/b > 0.5. The image on the left above satisfies the FR1 criterion (a/b < 0.5), and the image on the right satisfies the FR2 criterion (a/b > 0.5). All distances are in arcsec.