A head-tail galaxy has jets emerging from the core of the galaxy which are bent by interacting with the intracluster medium (ICM). The study of head-tail galaxies provides insights into the mechanisms of shock waves and turbulence, as well as magnetic-field amplification and cosmic-ray acceleration. A recent MeerKAT observation revealed that a head-tail galaxy in the galaxy cluster Abell 3322 exhibits a peculiar “Omega” structure in its shape.

Kurahara et al. investigated this Omega-tail galaxy further using the upgraded Giant Meterwave Radio Telescope (GMRT) and the Australia Telescope Compact Array (ATCA), and also examined Rapid ASKAP Continuum Survey (RACS) data. ATCA observations at 5.5 and 9.0 GHz resulted in the detection of the core of the Omega-tail galaxy, which is firmly associated with an optical galaxy. The 5 GHz ATCA and ASKAP RACS-low observations detected only the southern jet, revealing that the southern jet is brighter than the northern jet by a factor of ~2. This can be attributed to Doppler boosting and the inclination angle of the jets to our line of sight. Broadband data suggest that the radio spectrum becomes steeper along the jet propagation direction, with a further gradient of the spectral index perpendicular to the jet propagation also found. The team suggest that this indicates the presence of a shock wave along one side of the jets. The resultant ram pressure as well as the backflow made at the early stage of the jet may produce the tail component of this Omega-tail galaxy.

The composite image above combines Chandra X-ray (cyan-contour), DSS2 optical (white), and MeerKAT radio (red) data. The primary target of this study, referred to as the “Omega-tail galaxy”, is labeled along with its various structural components.