Many large elliptical galaxies are ensconced within a gaseous halo that, like the intracluster medium
, is hot and emits X-rays.
In particular, details of the formation of galactic winds and their impact on the external intergalactic or intracluster medium
(see Section 9) can be extremely beneficial in large-scale simulations where these effects are usually treated very crudely.
In rich clusters such as Virgo, the rate at which the intracluster medium radiates suggests that hundreds of solar masses of cold gas should be falling into the central galaxy (M87) each year.
There is only one way out of this conundrum: something must be heating the central regions of the intracluster medium to offset the cooling.
Instead, X-ray images from Chandra and XMM-Newton show bubbles, shock waves, ripples, and filaments within the intracluster medium of many galaxy clusters (S&T: May 2002, page 20, and December 2003, page 18).