X-shaped radio galaxies are distinguished from the classical double-lobed radio sources (i.e., FRI and FRII) by their peculiar large-scale radio morphology. In addition to the primary, active lobes, defined as such by having an overall higher surface brightness, they have a secondary pair of wings. These wings are located on each side of the nucleus and at large angles relative to the primary lobes, thus giving the impression of an ‘X'. Whereas agreement exists about the fact that only the pair of lobes is actively fed by radio plasma, it is not clear how the wings formed. The speaker will disucss our present understanding of the origin X-shaped radio galaxies which fall roughly into two main schools of thought: the wings are either (i) relic emission from previously active lobes or (ii) backflow emission from the primary, now active lobes as well as their future prospects.
