A Measurement of Gas Temperatures in Galaxy Clusters using the Relativistic Sunyaev-Zeldovich Effect

Understand

The hot gas in clusters of galaxies creates a distinctive spectral distortion in the cosmic microwave background (CMB) via the Sunyaev-Zeldovich (SZ) effect.

• To first order, the shape of the spectral distortion is fixed, but relativistic corrections (rSZ) introduce a dependence on the gas temperature.
• In this paper, we extract fluxes from a sample of 47 clusters in the Planck maps and make a ~5$\sigma$ detection of the rSZ effect by measuring the scaling relation between the SZ amplitude (a proxy for cluster mass) and the cluster temperature.
• Our measurement requires no prior knowledge of the clusters' gas temperatures and hence is an example of how the rSZ can be used to probe fundamental astrophysics.