Bayesian galaxy shape measurement for weak lensing surveys – III. Application to the Canada–France–Hawaii Telescope Lensing Survey
Bayesian galaxy shape measurement for weak lensing surveys – III. Application to the Canada–France–Hawaii Telescope Lensing Survey
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DOI：
10.1093/mnras/sts454
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发表时间：
2012-10
影响因子：
4.8
通讯作者：
L. Miller;C. Heymans;T. Kitching;L. Waerbeke;T. Erben;H. Hildebrandt;H. Hildebrandt;H. Hoekstra-
中科院分区：
文献类型：
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作者：
L. Miller;C. Heymans;T. Kitching;L. Waerbeke;T. Erben;H. Hildebrandt;H. Hildebrandt;H. Hoekstra-
描述了一种基于似然的方法，用于测量深部星系巡天中的弱引力透镜剪切力，并将其应用于加拿大-法国-夏威夷望远镜（CFHT）透镜巡天（CFHTLenS）。 CFHTLenS 包含来自 CFHT Legacy Survey 的 154 deg^2 多色光学数据，透镜测量是在 i′ 波段进行的，深度为 i′_(AB) < 24.7，对于信噪比 ν_(SN) ≳ 10 的星系。该方法基于早期论文中描述的 Lensfit 算法，但在这里我们描述了一个考虑到实际巡天属性的完整分析流程。该方法创建了单个图像曝光中变化的点扩散函数 (PSF) 的基于像素的模型。它适合 PSF 卷积二元（圆盘加核球）模型来测量每个星系的椭圆率，并对星系位置、大小、亮度和核球分数等模型干扰参数进行贝叶斯边缘化。该方法允许对多个抖动图像曝光进行最佳联合测量，同时考虑到成像失真和多个测量的对齐。我们讨论噪声偏差对星系椭圆率似然分布的影响。创建了两组反映 CFHTLenS 观察到的特性的图像模拟，以确定该方法的准确性并得出对噪声偏差影响的经验校正。
A likelihood-based method for measuring weak gravitational lensing shear in deep galaxy surveys is described and applied to the Canada–France–Hawaii Telescope (CFHT) Lensing Survey (CFHTLenS). CFHTLenS comprises 154 deg^2 of multi-colour optical data from the CFHT Legacy Survey, with lensing measurements being made in the i′ band to a depth i′_(AB) < 24.7, for galaxies with signal-to-noise ratio ν_(SN) ≳ 10. The method is based on the lensfit algorithm described in earlier papers, but here we describe a full analysis pipeline that takes into account the properties of real surveys. The method creates pixel-based models of the varying point spread function (PSF) in individual image exposures. It fits PSF-convolved two-component (disc plus bulge) models to measure the ellipticity of each galaxy, with Bayesian marginalization over model nuisance parameters of galaxy position, size, brightness and bulge fraction. The method allows optimal joint measurement of multiple, dithered image exposures, taking into account imaging distortion and the alignment of the multiple measurements. We discuss the effects of noise bias on the likelihood distribution of galaxy ellipticity. Two sets of image simulations that mirror the observed properties of CFHTLenS have been created to establish the method's accuracy and to derive an empirical correction for the effects of noise bias.