Measurement of the $T_{\rm CMB}$ evolution from the Sunyaev-Zel'dovich effect

In the standard hot cosmological model, the black-body temperature of the Cosmic Microwave Background (CMB), $T_{\rm CMB}$, increases linearly with redshift. Across the line of sight CMB photons interact with the hot ($\sim10^{7-8}$ K) and diffuse gas of electrons from galaxy clusters. This interaction leads to the well known thermal Sunyaev-Zel'dovich effect (tSZ), which produces a distortion of the black-body emission law, depending on $T_{\rm CMB}$. Using tSZ data from the ${\it Planck}$ satellite it is possible to constrain $T_{\rm CMB}$ below z=1. Focusing on the redshift dependance of $T_{\rm CMB}$ we obtain $T_{\rm CMB}(z)=(2.726\pm0.001)\times (1+z)^{1-β}$ K with $β=0.009\pm0.017$, improving previous constraints. Combined with measurements of molecular species absorptions, we derive $β=0.006\pm0.013$. These constraints are consistent with the standard (i.e. adiabatic, $β=0$) Big-Bang model.

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