2024/06/25 by Roan Haggar, Haggar, Roan, Yuba Amoura +9 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries
paper · pdf · doi:10.48550/arxiv.2406.17849
openalex publication_date 2024/06/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Cosmological parameters such as Ω_\rmM and σ8 can be measured indirectly using various methods, including galaxy cluster abundance and cosmic shear. These measurements constrain the composite parameter S8, leading to degeneracy between Ω_\rmM and σ8. However, some structural properties of galaxy clusters also correlate with cosmological parameters, due to their dependence on a cluster's accretion history. In this work, we focus on the splashback radius, an observable cluster feature that represents a boundary between a cluster and the surrounding Universe. Using a suite of cosmological simulations with a range of values for Ω_\rmM and σ8, we show that the position of the splashback radius around cluster-mass halos is greater in cosmologies with smaller values of Ω_\rmM or larger values of σ8. This variation breaks the degeneracy between Ω_\rmM and σ8 that comes from measurements of the S8 parameter. We also show that this variation is, in principle, measurable in observations. As the splashback radius can be determined from the same weak lensing analysis already used to estimate S8, this new approach can tighten low-redshift constraints on cosmological parameters, either using existing data, or using upcoming data such as that from Euclid and LSST.