A radio approach to the cool core -- non cool core dichotomy
  From the point of view of X-ray astronomers, galaxy clusters are usually
divided into two classes: "cool core"(CC) and "non-cool core" (NCC) objects.
The origin of this dichotomy has been subject of debate in recent years,
between "evolutionary" models (where clusters can evolve from CC to NCC, mainly
through mergers) and "primordial" models (where the state of the cluster is
fixed "ab initio" by early mergers or pre-heating). We found that in a
representative sample (clusters in the GMRT Radio halo survey with available
X-ray data), none of the objects hosting a giant radio halo can be classified
as a cool core. This result suggests that the main mechanisms which can produce
the ingredients to start a large scale synchrotron emission (most likely
mergers) are the same that can destroy CC and therefore strongly supports
"evolutionary" models of the CC-NCC dichotomy.
