Seminaire Lagrange -- Laura Salvati (IAS) -- Tracing Large-Scale Structure with the Thermal Sunyaev-Zeldovich Effect: Modelling, Challenges, and Observational Insights

Tracing Large-Scale Structure with the Thermal Sunyaev-Zeldovich Effect: Modelling, Challenges, and Observational Insights

The thermal Sunyaev-Zeldovich (tSZ) effect offers a unique window into the distribution of hot gas in the late-time Universe, making it a powerful probe of large-scale structure. It is extensively used to detect galaxy clusters, serving both cosmological and astrophysical investigations. The angular power spectrum of the tSZ signal is sensitive to a wide range of spatial scales—from the largest galaxy clusters to smaller groups and cosmic filaments.

Galaxy clusters, the most massive gravitationally bound structures in the Universe, are vital cosmological tools. They provide strong constraints on the matter distribution in the recent Universe. A key challenge in cluster cosmology is the accurate measurement of cluster mass—an essential ingredient in any analysis. However, cluster masses cannot be directly observed. Instead, we rely on scaling relations that link observable quantities—such as galaxy counts, pressure, temperature, and luminosity profiles—to the underlying mass. These relations depend critically on our understanding of baryon distribution within dark matter halos, as well as the astrophysical processes that influence this distribution.

In this talk, I will focus on galaxy clusters detected in the millimetre regime via the tSZ effect, incorporating complementary X-ray and optical data to calibrate cluster masses. I will present results from the analysis of various cluster observables and discuss how different modelling choices affect cosmological inferences. Finally, I will show how the tSZ power spectrum—taken as a whole—can be used to trace the cosmological evolution of large-scale structures.