Biases in, and corrections to, KSB shear measurements
Biases in, and corrections to, KSB shear measurements
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KSB 剪切测量的偏差和修正
DOI：
10.1111/j.1365-2966.2010.17589.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
Bartelmann
中科院分区：
文献类型：
--
作者：
Melchior;Bartelmann
我们分析了Kaiser-Squires-Broadhurst （KSB）方法从小而嘈杂的星系图像的表面亮度矩估计引力剪切。我们确定了三个潜在的有问题的假设。这些内容如下。(1)虽然引力剪切必须从平均星系图像中估计，但KSB从每个单独的图像中获得剪切估计值，然后取平均值。由于两个操作不交换，KSB给出了有偏差的结果。(2) KSB隐式假设星系椭圆率很小，而弱引力透镜只保证由于剪切引起的椭圆率变化很小。(3) KSB不反转卷积与点扩散函数（PSF），但给出了一个近似的PSF校正-即使是圆形的PSF -只在圆形源的限制。假设(2)和(3)的影响以一种依赖于权重函数和PSF宽度的方式部分抵消。我们定量地证明了由于所有假设造成的偏差，将KSB方法一致地扩展到剪切和椭圆的三阶，并表明这种扩展大大降低了偏差。适当的PSF反卷积问题将在Melchior等人的文章中讨论。
We analyse the Kaiser–Squires–Broadhurst (KSB) method to estimate gravitational shear from surface-brightness moments of small and noisy galaxy images. We identify three potentially problematic assumptions. These are as follows. (1) While gravitational shear must be estimated from averaged galaxy images, KSB derives a shear estimate from each individual image and then takes the average. Since the two operations do not commute, KSB gives biased results. (2) KSB implicitly assumes that galaxy ellipticities are small, while weak gravitational lensing only assures that the change in ellipticity due to the shear is small. (3) KSB does not invert the convolution with the point spread function (PSF), but gives an approximate PSF correction which – even for a circular PSF – holds only in the limit of circular sources. The effects of assumptions (2) and (3) partially counteract in a way dependent on the width of the weight function and of the PSF. We quantitatively demonstrate the biases due to all assumptions, extend the KSB approach consistently to third order in the shear and ellipticity and show that this extension lowers the biases substantially. The issue of proper PSF deconvolution will be addressed in Melchior et al.
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影响因子：
6.5
作者：
Peter Melchior;A. Boehnert;M. Lombardi;M. Bartelmann
通讯作者：
Peter Melchior;A. Boehnert;M. Lombardi;M. Bartelmann
从堆叠图像估计星系剪切力
DOI：
10.1111/j.1365-2966.2009.15161.x
发表时间：
2009
影响因子：
4.8
作者：
A. Lewis
通讯作者：
A. Lewis
DOI：
10.1111/j.1365-2966.2006.10198.x
发表时间：
2006-05-21
影响因子：
4.8
作者：
Heymans, C;Van Waerbeke, L;Wittman, D
通讯作者：
Wittman, D
DOI：
10.1111/j.1365-2966.2010.16598.x
发表时间：
2010-07-01
影响因子：
4.8
作者：
Bridle, Sarah;Balan, Sreekumar T.;Wittman, David
通讯作者：
Wittman, David