This is the third in a series of papers studying the astrophysics and cosmology of massive , dynamically relaxed galaxy clusters .
Our sample comprises 40 clusters identified as being dynamically relaxed and hot ( i.e. , massive ) in Papers I and II of this series .
Here we consider the thermodynamics of the intracluster medium , in particular the profiles of density , temperature and related quantities , as well as integrated measurements of gas mass , average temperature , total luminosity and center-excluded luminosity .
We fit power-law scaling relations of each of these quantities as a function of redshift and cluster mass , which can be measured precisely and with minimal bias for these relaxed clusters using hydrostatic arguments .
For the thermodynamic profiles , we jointly model the density and temperature and their intrinsic scatter as a function of radius , thus also capturing the behavior of the gas pressure and entropy .
For the integrated quantities , we also jointly fit a multidimensional intrinsic covariance .
Our results reinforce the view that simple hydrodynamical models provide a good description of relaxed clusters outside their centers , but that additional heating and cooling processes are important in the inner regions ( radii r { \raise - 3.225 pt \hbox { $ \buildrel < \over { \sim } $ } } 0.5 r _ { 2500 } \approx 0.15 % r _ { 500 } ) .
The thermodynamic profiles remain regular , with small intrinsic scatter , down to the smallest radii where deprojection is straightforward ( \sim 20 kpc ) ; within this radius , even the most relaxed systems show clear departures from spherical symmetry .
Our results suggest that heating and cooling are continuously regulated in a tight feedback loop , allowing the cluster atmosphere to remain stratified on these scales .