减小团簇尺度弱透镜的系统误差
Reducing Systematic Error in Cluster Scale Weak Lensing
摘要：
弱透镜提供了一个重要的途径，收集样本的星系团的质量选择。图像缩小过程中的细微系统误差会损害该技术的性能。我们使用B模式信号来量化这个系统误差，并测试减少这个误差的方法。我们表明，两个程序是有效的抑制系统误差在B模式：（1）细化的镶嵌CCD翘曲程序，以符合绝对天体坐标和（2）截断的平滑程序的规模为10 $^{\prime}$。这些程序的应用将系统误差减小到其原始幅度的20%。我们提供了一个解析表达式的分布中的最高峰的噪声地图，可用于估计的分数的假峰的弱透镜$κ$ -S/N地图作为检测阈值的函数。基于该分析，我们选择阈值S/N = 4.56，用于识别覆盖总面积为$\sim 3$ deg $^2$的两个测试场中的弱透镜峰的未污染集合。这些字段加在一起包含高于阈值的七个峰值。其中，六个是可能的星系系统，一个是叠加星系。我们证实了这些峰的可靠性与密集的红移调查，X射线和成像观测。我们采用的系统误差减小方法是通用的，可以应用于未来的大面积弱透镜测量。我们的高峰值分析表明，在信噪比阈值为4.5的情况下，即使在1000度$^2$的区域中，也应该只有2.7个伪弱透镜峰，其中我们基于斯巴鲁场预期$\sim$ 2000个峰。
英文摘要：
Weak lensing provides an important route toward collecting samples of clusters of galaxies selected by mass. Subtle systematic errors in image reduction can compromise the power of this technique. We use the B-mode signal to quantify this systematic error and to test methods for reducing this error. We show that two procedures are efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10$^{\prime}$. Application of these procedures reduces the systematic error to 20% of its original amplitude. We provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the weak lensing $κ$-S/N maps as a function of the detection threshold. Based on this analysis we select a threshold S/N = 4.56 for identifying an uncontaminated set of weak lensing peaks in two test fields covering a total area of $\sim 3$deg$^2$. Taken together these fields contain seven peaks above the threshold. Among these, six are probable systems of galaxies and one is a superposition. We confirm the reliability of these peaks with dense redshift surveys, x-ray and imaging observations. The systematic error reduction procedures we apply are general and can be applied to future large-area weak lensing surveys. Our high peak analysis suggests that with a S/N threshold of 4.5, there should be only 2.7 spurious weak lensing peaks even in an area of 1000 deg$^2$ where we expect $\sim$ 2000 peaks based on our Subaru fields.
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