case western reserve university



Heating and Cooling in Galaxy Clusters

Greg Bryan (Columbia)

The new X-ray observatories have unleashed an explosion of data about the hot gas in galaxy clusters, in the process overturning cherished theories and posing new puzzles, particularly about the impact of AGN on the thermal state of the cluster gas. I review what can be understood from observations, simple theory and high-resolution numerical simulations, showing that in some areas -- such as the temperature profile at large radii -- the latest observational results are in surprisingly good agreement with theory. On the other hand, the impact of cooling and heating on the core and on global scaling relations, is still not well understood. I use new simulations to show that there are, in fact, two separate heating/cooling problems in galaxy clusters and the resolution of these issues may be telling us something very important about high-redshift galaxy formation.