Shear calibration biases in weak-lensing surveys
Shear calibration biases in weak-lensing surveys
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DOI：
10.1046/j.1365-8711.2003.06683.x
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发表时间：
2003-01
影响因子：
4.8
通讯作者：
C. Hirata;U. Seljak
中科院分区：
文献类型：
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作者：
C. Hirata;U. Seljak
我们研究了当前弱透镜分析方法中由观察到的图像形状和剪切畸变之间的转换引起的偏差。这种总体校准偏差无法通过E/B分解或恒星校准等标准测试检测到。我们发现，点扩散函数的非高斯性有很大的影响，根据不同的分析方法，可以导致波动σ 8的线性幅度误差高达15%。这可以解释最近在弱透镜效应的振幅测定中看到的一些差异。利用椭圆拉盖尔展开法，我们开发了一种再高斯化方法，即使对分辨率较差的星系，也能将误差降低到1%的校准误差。我们还讨论了一种新型的剪切选择偏差，它会导致对信号的估计大约低估8%。它预计与红移比例，诱导误差在生长因子提取，如果没有适当的纠正。如果弱透镜效应要成为对宇宙学的高精度探测，理解和纠正对这种效应的恐惧是至关重要的。
We investigate biases induced by the conversion between the observed image shape and shear distortion in current weak-lensing analysis methods. Such overall calibration biases cannot be detected by the standard tests such as E/B decomposition or calibration with stars. We find that the non-Gaussianity of the point spread function has a significant effect and can lead to an error of up to 15 per cent on the linear amplitude of fluctuations σ 8 , depending on the method of analysis. This could explain some of the discrepancies seen in recent amplitude determinations from weak lensing. Using an elliptical Laguerre expansion method we develop a re-Gaussianization method that reduces the error to a calibration error of the order of 1 per cent, even for poorly resolved galaxies. We also discuss a new type of shear selection bias, which results in up to roughly an 8 per cent underestimation of the signal. It is expected to scale with redshift, inducing errors in the growth factor extraction if not properly corrected for. Understanding and correcting fear such effects is crucial if weak lensing is to become a high-precision probe of cosmology.