Cosmological Model Predictions for Weak Lensing: Linear and Nonlinear Regimes
Cosmological Model Predictions for Weak Lensing: Linear and Nonlinear Regimes
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弱透镜的宇宙学模型预测：线性和非线性机制
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
U. Seljak
中科院分区：
文献类型：
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作者：
B. Jain;U. Seljak
大尺度结构的弱透镜效应导致遥远星系图像中的相关椭圆率。两点相关性由沿视线沿着的物质功率谱确定。我们使用功率谱的完全非线性演化来计算预测的椭圆相关。为了探索约束宇宙学参数的最佳策略，我们给出了角标度θ = 1 '-3 °的不同二阶矩测量结果和不同的功率谱归一化结果。标准化到观测到的星系团丰度，在15'半径内椭圆率的均方根振幅为0.01z s0.6，几乎与宇宙学模型无关，其中zs是背景星系的中值红移。功率谱演变中的非线性效应显著增强了θ <10“的椭圆率--对于θ <1”，均方根椭圆率为1.05，几乎是线性预测的两倍。这种增强意味着对于2' < θ < 2°，椭圆率的信噪比仅随着角度微弱地增加，这与线性理论的预期不同，线性理论的预期是信噪比在度尺度上强烈地达到峰值。由于非线性效应，宇宙学参数的标度也发生了变化。通过测量小（非线性）和大（线性）角标度上的相关性，不同的宇宙学参数可以独立地被约束，以获得功率谱振幅和物质密度Ωm的模型独立估计。非线性效应也改变了椭圆率的概率分布。使用二阶微扰理论，我们发现，在大多数的范围内的利益有显着偏离正态分布。
Weak lensing by large-scale structure induces correlated ellipticities in the images of distant galaxies. The two-point correlation is determined by the matter power spectrum along the line of sight. We use the fully nonlinear evolution of the power spectrum to compute the predicted ellipticity correlation. We present results for different measures of the second moment for angular scales θ ≃ 1'-3° and for alternative normalizations of the power spectrum, in order to explore the best strategy for constraining the cosmological parameters. Normalizing to observed cluster abundance, the rms amplitude of ellipticity within a 15' radius is ≃0.01z s0.6, almost independent of the cosmological model, with zs being the median redshift of background galaxies. Nonlinear effects in the evolution of the power spectrum significantly enhance the ellipticity for θ < 10'—for θ ≃ 1' the rms ellipticity is ≃0.05, which is nearly twice as large as the linear prediction. This enhancement means that the signal-to-noise ratio for the ellipticity is only weakly increasing with angle for 2' < θ < 2°, unlike the expectation from linear theory that the signal-to-noise ratio is strongly peaked on degree scales. The scaling with cosmological parameters also changes because of nonlinear effects. By measuring the correlations on small (nonlinear) and large (linear) angular scales, different cosmological parameters can be independently constrained to obtain a model-independent estimate of both power spectrum amplitude and matter density Ωm. Nonlinear effects also modify the probability distribution of the ellipticity. Using second-order perturbation theory, we find that over most of the range of interest there are significant deviations from a normal distribution.