We present an analysis of 20 galaxy clusters observed with the Chandra X-ray satellite , focussing on the temperature structure of the intracluster medium and the cooling time of the gas .
Our sample is drawn from a flux-limited catalogue but excludes the Fornax , Coma and Centaurus clusters , owing to their large angular size compared to the Chandra field-of-view .
We describe a quantitative measure of the impact of central cooling , and find that the sample comprises 9 clusters possessing cool cores and 11 without .
The properties of these two types differ markedly , but there is a high degree of uniformity amongst the cool core clusters , which obey a nearly universal radial scaling in temperature of the form T \propto r ^ { \sim 0.4 } , within the core .
This uniformity persists in the gas cooling time , which varies more strongly with radius in cool core clusters ( t _ { \mathrm { cool } } \propto r ^ { \sim 1.3 } ) , reaching t _ { \mathrm { cool } } < 1 Gyr in all cases , although surprisingly low central cooling times ( < 5 Gyr ) are found in many of the non-cool core systems .
The scatter between the cooling time profiles of all the clusters is found to be remarkably small , implying a universal form for the cooling time of gas at a given physical radius in virialized systems , in agreement with recent previous work .
Our results favour cluster merging as the primary factor in preventing the formation of cool cores .