A radio approach to the cool core -- non cool core dichotomy

TL;DR

This study uses radio observations to investigate the origin of the cool core versus non-cool core classification in galaxy clusters, providing evidence that mergers play a key role in this dichotomy.

Contribution

It demonstrates a correlation between giant radio halos and the absence of cool cores, supporting evolutionary models over primordial ones.

Findings

Clusters with giant radio halos lack cool cores.

Radio halos are associated with merger activity.

Supports the idea that mergers destroy cool cores.

Abstract

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.