Information content of weak lensing power spectrum and bispectrum: including the non-Gaussian error covariance matrix
Information content of weak lensing power spectrum and bispectrum: including the non-Gaussian error covariance matrix
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DOI：
10.1093/mnras/sts340
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发表时间：
2012-07
影响因子：
4.8
通讯作者：
I. Kayo;M. Takada;U. BhuvneshJainToho;Kavli Ipmu;Upenn
中科院分区：
文献类型：
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作者：
I. Kayo;M. Takada;U. BhuvneshJainToho;Kavli Ipmu;Upenn
我们通过对功率谱和双谱的所有相关协方差进行建模，对Lambda-CDM模型和解析光晕模型使用1000个光线跟踪模拟实现，来解决弱透镜调查的非高斯区域中的信息量。我们发展了一种形式来描述所有三角形构型的功率谱和双谱的协方差矩阵。除了已知的扩展到六点相关函数的贡献外，我们还提出了一个新的贡献，即晕样本方差(HSV)，这是由透镜傅立叶模与大尺度质量涨落的耦合产生的，该耦合在与勘测区相当的尺度上。结果表明，在考虑HSV的情况下，模型预测结果与模拟结果吻合较好。HSV对多极L和10^3的协方差矩阵的贡献占主导地位，它是由质量为>；10^14太阳质量和相对较低红移z<；0.4的大质量晕产生的。由于这种光晕很容易从多色成像调查中识别出来，因此可以从数据中估计其影响。通过在功率谱中加入双谱，总信息量或累积信噪比提高了20-50%，相当于仅功率谱测量的测量面积增加了1.4-2.3倍。然而，它仍然比高斯场的情况小3倍，这主要是由于HSV。因此，双谱测量对宇宙学是有用的，但使用来自即将到来的调查的信息需要仔细估计非高斯协方差。
We address the amount of information in the non-Gaussian regime of weak lensing surveys by modelling all relevant covariances of the power spectra and bispectra, using 1000 ray-tracing simulation realizations for a Lambda-CDM model and an analytical halo model. We develop a formalism to describe the covariance matrices of power spectra and bispectra of all triangle configurations. In addition to the known contributions which extend up to six-point correlation functions, we propose a new contribution `the halo sample variance (HSV)' arising from the coupling of the lensing Fourier modes with large-scale mass fluctuations on scales comparable with the survey region via halo bias theory. We show that the model predictions are in good agreement with the simulation once we take the HSV into account. The HSV gives a dominant contribution to the covariance matrices at multipoles l > 10^3, which arises from massive haloes with a mass of > 10^14 solar mass and at relatively low redshifts z < 0.4. Since such haloes are easily identified from a multi-colour imaging survey, the effect can be estimated from the data. By adding the bispectrum to the power spectrum, the total information content or the cumulative signal-to-noise ratio up to a certain maximum multipole of a few 10^3 is improved by 20--50 per cent, which is equivalent to a factor of 1.4--2.3 larger survey area for the power spectrum measurement alone. However, it is still smaller than the case of a Gaussian field by a factor of 3 mostly due to the HSV. Thus bispectrum measurements are useful for cosmology, but using information from upcoming surveys requires that non-Gaussian covariances are carefully estimated.