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23rd of February 2021
The remnant radio galaxy MIDAS J230104-334939
by Quici et al.
The extensive lobes of radio galaxies are powered by jets launched from the environment of the super-massive black hole at the core of the galaxy. During this active phase the core of the galaxy is often a bright, compact, flat-spectrum radio source. When these jets "switch off", the radio galaxy enters a remnant phase. Quici et al. have searched for radio galaxies in this phase by taking advantage of multi-frequency radio imaging of a sub-region of the GAMA 23 field. They examined data from the Murchison Wide-field Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). Adopting an "absent radio core" criterion, they identify 10 radio galaxies showing no evidence for an active nucleus and classify these as new candidate remnant radio galaxies.

The image above, of MIDAS J230104-334939, has a VIKING near-infrared image as the background. Three sets of contours are overlaid, representing the radio emission as seen by ASKAP (black), ATCA 5.5 GHz (orange) and ATCA 9.5 GHz (blue). A red marker is overlaid on the position of the potential host galaxy. The edge-brightened morphology exhibits clear hotspots in each lobe, which are detected by the ATCA at 5.5 and 9.5 GHz. The radio source is unambiguously associated with the host galaxy G1, at a redshift of 0.312, which almost perfectly aligns with the projected centre of the source. The results have been published in Publications of the Astronomical Society of Australia.

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