Cosmological parameters such as Ω_M and σ ₈ can be measured indirectly using various methods, including galaxy cluster abundance and cosmic shear. These measurements constrain the composite parameter S ₈, leading to degeneracy between Ω_M and σ ₈. 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_M and σ ₈, we show that the position of the splashback radius around cluster-mass halos is greater in cosmologies with smaller values of Ω_M or larger values of σ ₈. This variation breaks the degeneracy between Ω_M and σ ₈ that comes from measurements of the S ₈ 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 S ₈, 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.

中文翻译：

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使用星系团的溅射半径约束宇宙学参数


宇宙学参数，例如 Ω _M和σ ₈可以使用各种方法间接测量，包括星系团丰度和宇宙剪切力。这些测量限制了复合参数S ₈ ，导致 Ω _M和σ ₈ .然而，星系团的一些结构特性也与宇宙学参数相关，因为它们依赖于星系团的吸积历史。在这项工作中，我们关注溅回半径，这是一种可观察的星团特征，代表星团与周围宇宙之间的边界。使用一系列具有 Ω _M和 Ω M 值范围的宇宙学模拟σ_{如图 8}所示，我们表明，在 Ω _M值较小或 Ω M 值较大的宇宙学中，星团质量晕周围的飞溅半径位置较大。 σ ₈ .这种变化打破了 Ω _M和σ ₈来自测量S _8个参数。我们还表明，这种变化原则上是可以通过观察来测量的。由于溅射半径可以通过已用于估计的相同弱透镜分析来确定S_{如图 8}所示，这种新方法可以使用现有数据或使用即将到来的数据（例如来自 Euclid 和 LSST 的数据）收紧对宇宙学参数的低红移约束。