Discovery of X-shaped morphology of the giant radio galaxy 0503-286

Abstract

The high surface-brightness sensitivity of the galactic and extragalactic all-sky mwa survey (GLEAM) image of the giant radio galaxy (GRG) 0503-28 at 70–230 MHz has revealed an inversion-symmetric bending of its two lobes, while maintaining a ∼200 kpc wide strip-like radio emission gap between their bent portions. This lends the source the appearance of a mega-sized X-shaped radio galaxy. Identifying the emission gap with the presence of a gaseous layer, probably a WHIM-filled sheet in the cosmic web, we suggest that the layer is the most likely cause of the inversion-symmetric bending of the two radio lobes. Multiple observational manifestations of such gaseous layers are noted. The two lobes of this GRG, known to extend very asymmetrically from the host galaxy, are remarkably symmetric about the emission gap, confirming a curious trend noted earlier for double radio sources of normal dimensions. The anomalous radio spectral gradient reported for the northern lobe of this GRG is not substantiated.