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arXiv 1203.2138astro-ph.COgr-qc
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弱透镜测量中三点内禀自相关的自标定

Self-Calibration for 3-point Intrinsic Alignment Auto-Correlations in Weak Lensing Surveys

M. A. Troxel, Mustapha Ishak

摘要:

弱透镜信号(宇宙剪切)已被证明是强烈污染的各种类型的星系的内在排列(IA)的相关性,这构成了一个障碍,精确的弱透镜测量。IA信号的红移依赖性已被用于在2点的水平,以减少这种污染,只测量大的红移箱之间的互相关,这显着降低了星系的内在椭圆率-内在椭圆率(II)的相关性。一个自校准技术的基础上的红移依赖的IA相关性也被提出作为一种手段,以消除2点IA污染的透镜信号。我们在这里探索的红移依赖的IA和透镜双谱,以提出一个自校准的IA自相关在3点水平(即GGI,GII和III),这可以很好地理解,而无需任何特定的IA模型的假设。我们发现,未来的弱透镜调查将能够测量独特的IA红移依赖范围内的$|Δz^P|\le 0.2$。使用保守估计的照片-z精度,我们描述了3点自校准技术的总IA信号,这可以通过透镜层析成像的照片-z箱大小$\sim 0.01$。我们发现,在适当的约束条件下,三点自校准可以在红移分离的两点技术的精度。这使得这里提出的3点IA自相关自校准技术能够显著减少IA污染对弱透镜双谱的污染。

英文摘要:

The weak lensing signal (cosmic shear) has been shown to be strongly contaminated by the various types of galaxy intrinsic alignment (IA) correlations, which poses a barrier to precision weak lensing measurements. The redshift dependence of the IA signal has been used at the 2-point level to reduce this contamination by only measuring cross-correlations between large redshift bins, which significantly reduces the galaxy intrinsic ellipticity - intrinsic ellipticity (II) correlation. A self-calibration technique based on the redshift dependences of the IA correlations has also been proposed as a means to remove the 2-point IA contamination from the lensing signal. We explore here the redshift dependences of the IA and lensing bispectra in order to propose a self-calibration of the IA auto-correlations at the 3-point level (i.e. GGI, GII, and III), which can be well understood without the assumption of any particular IA model. We find that future weak lensing surveys will be able to measure the distinctive IA redshift dependence over ranges of $|Δz^P|\le 0.2$. Using conservative estimates of photo-z accuracy, we describe the 3-point self-calibration technique for the total IA signal, which can be accomplished through lensing tomography of photo-z bin size $\sim 0.01$. We find that the 3-point self-calibration can function at the accuracy of the 2-point technique with modest constraints in redshift separation. This allows the 3-point IA auto-correlation self-calibration technique proposed here to significantly reduce the contamination of the IA contamination to the weak lensing bispectrum.

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