Cool-core (CC) clusters dominate the local cluster population. Numerous X-ray studies have provided a detailed knowledge of the properties of the Intra cluster medium (ICM) in these systems, and multi-wavelength data have shown that the CC phenomenon is regulated by complex physics involving interactions of the ICM with the brightest cluster galaxy. The dominant heating source that prevents the over-cooling catastrophe of the ICM is likely to be an AGN fueling a massive central black hole and leading to an outburst which can heat the ICM.
In this talk we present recent results of the most exhaustive study of the evolution of CCs out to redshift z=1.3. Using high-resolution Chandra data, we obtained a robust measure of the surface brightness concentration parameter, C_SB, which is an excellent proxy of the cooling time. Relying on three representative cluster samples spanning different redshifts we assess quantitatively the change in the CC strength distribution. At variance with previous results, we find a moderate evolution of the cool-core population with redshift, while confirming the lack of strong CC at z>0.5, which significantly constrains their formation time scales.
In addition, we present the deepest Chandra observation (370 ksec) of a distant cluster, WARPSJ1415 at z=1.03, that shows a temperature drop towards the cluster core of about half of the global ICM temperature, and probably the highest metallicity peak ever observed in galaxy clusters. This data unambiguously demonstrates that at z=1, a cool core cluster has ICM properties similar to the ones of local cool-cores.
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