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.
