Are there cool-core clusters at high-redshift? Chandra results and
  prospects with WFXT
  In this contribution we trace the evolution of cool-core clusters out to
z~1.3 using high-resolution Chandra data of three representative cluster
samples spanning different redshift ranges. Our analysis is based on the
measurement of the surface brightness (SB) concentration, c_SB, which strongly
anti-correlates with the central cooling time and allows us to characterize the
cool-core strength in low S/N data. We confirm a negative evolution in the
fraction of cool-core clusters with redshift, in particular for very strong
cool-cores. Still, we find evidence for a large population of well formed
cool-cores at z ~ 1. This analysis is potentially very effective in
constraining the nature and the evolution of the cool-cores, once large samples
of high-z clusters will be available. In this respect, we explore the potential
of the proposed mission Wide Field X-ray Telescope (WFXT) to address this
science case. We conclude that WFXT provides the best trade-off of angular
resolution, sensitivity and covered solid angle in order to discover and fully
characterize the cool-core cluster population up to z=1.5.
