Drag heating of gas in rich superclusters

Since the basic properties of galactic superclusters (SCs) are of considerable interest in studies of the large-scale structure of the universe, it is essential to extend our view of SCs beyond the optical region of the electromagnetic spectrum. It is pointed out here that clusters moving through an intracluster gas of density about 10 exp -6/cu cm experience strong gravitational drag, and the associated heating probably raises the gas temperature up to about 5 x 10 exp 7 K. A search should be made for this gas in the few-keV region.