Magnetic fields, heating and thermal conduction in halos, and the suppression of cooling flows

Arguments against the existence of massive cooling flows in the central region of giant elliptical galaxies are presented. The difficulties of cooling flow models and how these difficulties can be resolved with thermal conduction and internal heating are discussed. It is shown that a stable form of cosmic-ray heating is possible, that the possible reduction of thermal conduction by tangled magnetic fields has been greatly overestimated, and that fine tuning of heating and radiative losses can be achieved in a self-regulating manner. A consistent description of the physics must include the effects of thermal conduction in the analysis of the flows. 59 references