Speaker
Description
The angular power spectrum of galaxy clusters and groups is sensitive to $S_8 = \sigma_8(\Omega_m/0.3)^{1/2}$, the cosmological parameter that is currently in tension among different cosmological probes. In this work we present measurements of the X-ray angular power spectra of clusters and groups from the half-sky map constructed from the publicly available eRASS1 data. Owing to eRASS1’s extensive sky coverage, its power spectrum achieves unprecedented precision compared to measurements from Chandra, XMM-Newton, and eFEDS. Using a well-calibrated, physical cluster gas model that includes astrophysics of feedback and non-thermal pressure support, we obtain constraints on $\sigma_8$ and $\Omega_M$, marginalized over astrophysics. Our constraints are competitive to, and complementary to other cluster cosmological probes, as they are not subject to cluster count systematics, such as mass calibration and selection bias. We show that future cross-correlations with multi-wavelength surveys such as SZ from CMB-4, and optical from Rubin/Euclid/Roman, will not only provide improved constraints on $S_8$, but also on other cosmological parameters such as the Dark energy Equation of State.
