Clusters of Galaxies and Cooling Hot Gas

This review describes the information derived from Einstein X-ray imaging observations which is relevant to cooling flows in clusters of galaxies. It describes the properties of those clusters which have cooling flows and their relative proportions compared to other non-cooling flow clusters. A method for deriving quantitative parameters (gas densities and cooling times) is described and the results are compared with other techniques for estimating the importance of cooling. Finally, several effects of cooling flows around galaxies in clusters are discussed.