Cosmology with the SZ spectrum: measuring the Universe's temperature with galaxy clusters

TL;DR

This paper demonstrates how galaxy clusters' Sunyaev-Zel'dovich effect can measure the CMB temperature at various redshifts and forecasts future constraints on CMB spectral distortions using upcoming experiments.

Contribution

It presents the first measurements of the CMB temperature at different redshifts using SZ effect data from Planck and forecasts future constraints on CMB spectral distortions.

Findings

Measured $T_{CMB}(z)$ for 75 galaxy clusters.

Forecasts improved constraints on y-type spectral distortion.

Demonstrated potential of SZ effect for cosmological temperature measurements.

Abstract

The hot gas in clusters of galaxies creates a distinctive spectral distortion in the cosmic microwave background (CMB) via the Sunyaev-Zel'dovich (SZ) effect. The spectral signature of the SZ can be used to measure the CMB temperature at cluster redshift ($T_{\rm CMB}(z)$) and to constrain the monopole of the y-type spectral distortion of the CMB spectrum. In this work, we start showing the measurements of $T_{\rm CMB}(z)$ for a sample extracted from the Second Catalog of galaxy clusters produced by Planck (PSZ2) and containing 75 clusters selected from CHEX-MATE. Then we show the forecasts for future CMB experiments about the constraints on the monopole of the y-type spectral distortion of the CMB spectrum via the spectrum of the SZE.