Hot gas and magnetic fields in clusters of galaxies
Many clusters of galaxies contain large quantities of hot diffuse gas. I have studied the properties of waves in this gas using Lagrangian perturbations. The gas is far more thermally stable than is commonly thought. For bremsstrahlung cooling, all modes that remain oscillatory are damped. Galaxy motions, especially the oscillations of a central cD galaxy, are an important way of generating large amplitude waves in cluster gas. This is especially pertinent in view of the growing realization that cD galaxies are not at rest with respect to the cluster. I also present evidence that weak magnetic fields tangled on scales of ~ 10 kpc are common in cluster gas. Electrons responsible for the flow of heat in the gas must travel along the field lines, leading to a global reduction in heat flux. The superposition of many different field lines implies that the cluster gas is a multiphase medium. Such a picture has been suggested independently by the claimed observation of mass drop-out from cooling flows. I also show some results from a more advanced study using real magnetic fields rather than random walk models.