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R.D. Blandford (Caltech)
Recent observations of rich clusters of galaxies can be interpreted as suggesting that cooling gas vanishes when it reaches keV temperatures only to reappear at temperatures below 100eV. One possible explanation of this is that the warm gas is supported in the cluster potential well by the pressure of GeV cosmic ray protons accelerated at the shock front where the gas acquired its entropy in the first place. If, as seems possible, this gas is well stirred it may be cooled non-radiatively by a relatively amount of cool gas with which it is mixed on lengthscales smaller than the mean free path of 10,000 km/s electrons. The viability of and some observational predictions associated with this interpretation will be discussed.
Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.