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Paper: Cool Core Clusters at Redshift z > 0.7
Volume: 399, Panoramic Views of Galaxy Formation and Evolution
Page: 375
Authors: Santos, J.S.; Rosati, P.; Tozzi, P.; Böhringer, H.; Ettori, S.; Bignamini, A.
Abstract: We present a study which aims at measuring the fraction of Cool Core (CC) Clusters in the distant galaxy cluster population, i.e., out to redshift 0.7 < z < 1.4. Using a morphologically heterogeneous sample of nearby (0.15 < z < 0.3) clusters drawn from the Chandra archive, we define criteria to characterize cool cores that are applicable to a high-z sample. We made a global surface brightness (SB) analysis, measuring radial SB profiles and we defined a surface brightness concentration, cSB, which is sensitive to the core properties. In addition, we measured the cooling time in inner regions with 20 kpc radius, thus evaluating central cooling in a more physical way. The overall SB analysis of the low-z sample indicates 3 categories of clusters: non-CC, moderate and strong CC, whereas in the high-z clusters we find only the first two regimes. The cooling time distribution supports this result, showing a strong negative correlation with cSB. Our analysis indicates a significant fraction of distant clusters harboring a moderate CC, similar to those found in the local sample. Nevertheless, strong CCs are not common at high-z, which could be related with the shorter age of these clusters.
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