Constraining CMB temperature evolution with Sunyaev-Zel'dovich galaxy clusters from the Atacama Cosmology Telescope

TL;DR

This study uses Sunyaev-Zel'dovich galaxy clusters from the Atacama Cosmology Telescope to test the evolution of the CMB temperature, finding results consistent with the standard adiabatic model and constraining dark energy decay.

Contribution

It provides new constraints on CMB temperature evolution using a large SZ-selected cluster sample, improving previous limits and linking deviations to dark energy decay.

Findings

No significant deviation from the standard adiabatic model.

Joint constraint on CMB temperature evolution parameter: α = -0.001 ± 0.012.

Dark energy effective equation of state constrained to w_eff ≈ -1.

Abstract

The Sunyaev-Zel'dovich (SZ) effect introduces a specific distortion of the blackbody spectrum of the cosmic microwave background (CMB) radiation when it scatters off hot gas in clusters of galaxies. The frequency dependence of the distortion is only independent of the cluster redshift when the evolution of the CMB radiation is adiabatic. Using 370 clusters within the redshift range $0.07\lesssim z\lesssim1.4$ from the largest SZ-selected cluster sample to date from the Atacama Cosmology Telescope, we provide new constraints on the deviation of CMB temperature evolution from the standard model $\alpha=0.017^{+0.029}_{-0.032}$, where $T(z)=T_0(1+z)^{1-\alpha}$. This result is consistent with no deviation from the standard adiabatic model. Combining it with previous, independent datasets we obtain a joint constraint of $\alpha=-0.001\pm0.012$. Attributing deviation from adiabaticity to the decay of dark energy, this result constrains its effective equation of state $w_\mathrm{eff}=-0.998^{+0.008}_{-0.010}$.