Confining the lobes of giant radio galaxies

Giant radio galaxies, which extend to more than 1 Mpc in size, pose a difficultphysical problem. The radio lobes that they generate must span regions of verydifferent gas density and pressure, and yet they maintain relatively uniformwidths over their entire structures. This is difficult to achieve unless thelobes are propagating through a medium which is more extended, and more uniform,than the gas in a cluster of galaxies. We propose to use XMM to image acarefullychosen set of four giant radio galaxies to detect Xray emission fromthis external gas, and so characterise this unusual, and potentiallycosmologicallyimportant, medium. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]