Speaker: erwin Lau (Harvard)
Cosmology and Astrophysics with Multiwavelength Cross-Correlations of Galaxy Clusters and Groups
The cosmic tension in the amplitude of matter density fluctuations, parameterized by S8, remains one of cosmology's outstanding puzzles. The angular power spectrum of galaxy clusters and groups has emerged as a powerful tool for investigating this tension, owing to its strong sensitivity to S8. In this talk, I present our analysis of X-ray angular power spectra derived from the eROSITA All Sky Survey data release 1 (eRASS1), which provides unprecedented precision through its extensive half-sky coverage. We employ a well-calibrated Baryon Pasting (BP) gas model that incorporates key astrophysical processes, to obtain the first S8 constraints from the eRASS1 angular power spectrum. Our results yield an S8 value that, while smaller than Planck CMB measurements, remains consistent within 1sigma and competitive with other cosmological probes. Beyond cosmology, our analysis provides novel constraints on cluster astrophysics, including feedback processes and non-thermal pressure support. I will conclude by examining both the challenges and opportunities for enhancing these constraints through future multi-wavelength surveys of galaxy clusters and groups across X-ray, microwave, and optical bands.
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