观测到的星系团X射线光度函数对修正引力的约束
Constraints on modified gravity from the observed X-ray luminosity function of galaxy clusters
摘要：
我们使用测量宇宙结构的增长，推断从观测到的演化的X射线光度函数（XLF）的星系团，约束偏离广义相对论（GR）的宇宙尺度。我们采用流行的增长率参数化，Omega_m（z）^gamma，GR预测的增长指数gamma~0.55。我们使用宇宙微波背景（CMB），Ia型超新星（SNIa）和X射线团簇气体质量分数（fgas）的观测，同时限制宇宙的膨胀历史和能量含量，如背景模型参数所描述的：Omega_m，w和Omega_k，即，平均物质密度、暗能量状态方程参数和平均曲率。使用保守的津贴系统的不确定性，特别是在XLF分析的质量-光度标度关系的演变，我们发现伽玛=0.51+0.16-0.15和欧米茄_m=0.27+-0.02（68.3%的置信限），一个平坦的宇宙学常数（LCDM）的背景模型。让w是一个自由参数，我们发现伽玛=0.44+0.17-0.15。放松LCDM模型中的平坦性先验，我们得到gamma=0.51+0.19-0.16。当除了XLF数据之外，我们还使用CMB数据通过ISW效应来约束gamma时，对于平坦LCDM模型，我们得到gamma=0.45+0.14-0.12的组合约束。我们的分析提供了迄今为止对增长指数最严格的限制。我们没有发现在宇宙学尺度上偏离广义相对论的证据。
英文摘要：
We use measurements of the growth of cosmic structure, as inferred from the observed evolution of the X-ray luminosity function (XLF) of galaxy clusters, to constrain departures from General Relativity (GR) on cosmological scales. We employ the popular growth rate parameterization, Omega_m(z)^gamma, for which GR predicts a growth index gamma~0.55. We use observations of the cosmic microwave background (CMB), type Ia supernovae (SNIa), and X-ray cluster gas-mass fractions (fgas), to simultaneously constrain the expansion history and energy content of the Universe, as described by the background model parameters: Omega_m, w, and Omega_k, i.e., the mean matter density, the dark energy equation of state parameter, and the mean curvature, respectively. Using conservative allowances for systematic uncertainties, in particular for the evolution of the mass-luminosity scaling relation in the XLF analysis, we find gamma=0.51+0.16-0.15 and Omega_m=0.27+-0.02 (68.3 per cent confidence limits), for a flat cosmological constant (LCDM) background model. Allowing w to be a free parameter, we find gamma=0.44+0.17-0.15. Relaxing the flatness prior in the LCDM model, we obtain gamma=0.51+0.19-0.16. When in addition to the XLF data we use the CMB data to constrain gamma through the ISW effect, we obtain a combined constraint of gamma=0.45+0.14-0.12 for the flat LCDM model. Our analysis provides the tightest constraints to date on the growth index. We find no evidence for departures from General Relativity on cosmological scales.
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