Mergers, cooling flows, and evaporation revisited

Sparks has recently proposed that the evaporation of cold gas clouds embedded in a hot intracluster medium can mimic the spectral appearance of a cooling flow without any cooling actually occurring. If correct, this would solve a major puzzle: the lack of clear evidence for large quantities of previously cooled material in cooling flow clusters. We show here that his evaporation model is untenable since it requires planar geometry to explain the observed X-ray spectra of cooling flows but is then in conflict with the observed X-ray images; the model investigated also has implausible boundary conditions. Moreover, the supposed evaporating region was itself embedded in a cooling flow, and the solution, which is assumed static, is highly unstable.