We have examined two cooling flow models that differ from the standard models in clusters of galaxies. The goal is to find a model in which the observations are reproduced without appealing to an unusual initial mass function for star formation. The most important observations to reproduce are the observed temperature gradient and lack of the young stars that would be produced if cooled gas formed stars. In one model, drag heating by galaxies reheats the cluster gas and also suppresses thermal instabilities in certain temperature regimes. Numerical hydrodynamic simulations show that it is possible to produce the observed temperature gradient while significantly reducing the cooling rate for the gas, but only for a narrow range of the galaxy heating parameter. In another model, the gas cools and begins to form stars, which lead to supernovae that reheat the cooled gas to the ambient cluster temperature. This model is viable if only high-mass stars are formed and if the supernovae are subluminous.
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Bregman et al. (1989) studied this question.