We have determined the CMB temperature , T ( z ) , at redshifts in the range 0.023-0.546 , from multi-frequency measurements of the S-Z effect towards 13 clusters .
We extract the parameter \alpha in the redshift scaling T ( z ) = T _ { 0 } ( 1 + z ) ^ { 1 - \alpha } , which contrasts the prediction of the standard model ( \alpha = 0 ) with that in non-adiabatic evolution conjectured in some alternative cosmological models .
The statistical analysis is based on two main approaches : using ratios of the S-Z intensity change , \Delta I , thus taking advantage of the weak dependence of the ratios on IC gas properties , and using directly the \Delta I measurements .
In the former method dependence on the Thomson optical depth and gas temperature is only second order in these quantities .
In the second method we marginalize over these quantities which appear to first order in the intensity change .
The marginalization itself is done in two ways - by direct integrations , and by a Monte Carlo Markov Chain approach .
Employing these different methods we obtain two sets of results that are consistent with \alpha = 0 , in agreement with the prediction of the standard model .