[IP2I seminar] Cosmology - C. Payerne (IRFU CEA, Saclay, FR) - Cosmology with galaxy clusters in the Rubin LSST era

jeudi 7 mai 2026, 11:00 → 12:00 Europe/Paris

Galaxy clusters are among the main cosmological tracers for probing the late-time universe, offering unique insight into how cosmic structure grows and what drives it, from dark matter to dark energy. With next-generation photometric surveys like the Vera C. Rubin Observatory’s LSST and Euclid set to deliver hundreds of thousands of optically selected clusters, we are entering an era of unprecedented statistical power. The current limiting factor of cluster number count cosmology is our knowledge of the cluster mass–proxy relation, which connects galaxy clusters' observables to the underlying cosmology-dependent halo mass distribution. To address this challenge, cluster number counts are usually combined with weak gravitational lensing, which probes the projected matter distribution within clusters. In this talk, I will present my contribution to the analysis framework developed within the LSST Dark Energy Science Collaboration (LSST DESC), and its application to the simulated LSST DESC DC2 dataset, by combining cluster abundance with weak gravitational lensing mass estimates to infer the mass-proxy relation jointly with cosmological parameters. Moreover, I will discuss the growing interest in simulation-based inference (SBI) methods for cluster cosmology, which enable forward modeling of both cluster abundance measurements and lensing observables without requiring explicit likelihood formulations, paving the way for more robust cosmological analyses using galaxy clusters.