of the baryonic matter and the nature of ‘feedback’ from radio-loud active galaxies. When discussing the evolution of hot gas, it is important to understand that, although powerful radio-loud AGN are rare, their impact can be long lived: a single FRII outburst can have an effect on the IGM surrounding the AGN galaxy that exceeds that of a large number of less violent, longer-lived low-power radio sources [@ba03] and many groups that no longer show signs of AGN may once have hosted FRII sources.

Detailed studies of the dynamics of radio galaxies using X-ray observations rely on the capability of separating the thermal and non-thermal emission from the source. Some of the non-thermal emission comes in the form of synchroton and inverse-Compton emission from the jets and hotspots, which is generally best studied at high resolution with [*Chandra*]{}. However, the dominant non-thermal component in powerful radio galaxies is inverse-Compton emission from the lobes. This occurs when electrons in the lobes scatter cosmic microwave background (CMB) photons to X-ray energies (e.g. @flmkf95; @tkmiiikty98 @hbchlw02; @ks05; @chhbbw05). To be able to separate the non-thermal and thermal components, we need to study objects where we can obtain a significant number of counts from 