Lack of cooling flow clusters at z>0.5
  The goal of this work is to study the incidence rate of "cooling flows" in the high redshift clusters using Chandra observations of z>0.5 objects from a new large, X-ray selected catalog. We find that only a very small fraction of high-z objects have cuspy X-ray brightness profiles, which is a characteristic feature of the cooling flow clusters at z~0. The observed lack of cooling flows is most likely a consequence of a higher rate of major mergers at z>0.5. 
A.Vikhlinin, R.Burenin, W.R.Forman, C.Jones, A.Hornstrup, S.S.Murray,   H.Quintana