High significance detection of the tSZ effect relativistic corrections
  The thermal Sunyaev-Zel'dovich (tSZ) effect is produced by the interaction of
cosmic microwave background (CMB) photons with the hot (a few keV) and diffuse
gas of electrons inside galaxy clusters integrated along the line of sight.
This effect produces a distortion of CMB blackbody emission law. This
distortion law depends on the electronic temperature of the intra-cluster hot
gas, $T_{e}$, through the so-called tSZ relativistic corrections. In this work,
we have performed a statistical analysis of the tSZ spectral distortion on
large galaxy cluster samples. We performed a stacking analysis for several
electronic temperature bins, using both spectroscopic measurements of X-ray
temperatures and a scaling relation between X-ray luminosities and electronic
temperatures. We report the first high significance detection of the
relativistic tSZ at a significance of 5.3 $\sigma$. We also demonstrate that
the observed tSZ relativistic corrections are consistent with X-ray deduced
temperatures. This measurement of the tSZ spectral law demonstrates that tSZ
effect spectral distorsion can be used as a probe to measure galaxy cluster
temperatures.
