Weak-lensing shear estimates with general adaptive moments, and studies of bias by pixellation, PSF distortions, and noise
Weak-lensing shear estimates with general adaptive moments, and studies of bias by pixellation, PSF distortions, and noise
复制标题
使用一般自适应矩的弱透镜剪切估计，以及通过像素化、PSF 失真和噪声进行的偏差研究
DOI：
10.1051/0004-6361/201629591
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
P. Schneider
中科院分区：
文献类型：
--
作者：
P. Simon;P. Schneider
在弱引力透镜中，星系图像中亮度轮廓的加权四极矩是估算引力切变的常用方法。我们采用一般自适应矩（GLAM）研究剪切偏置的根本原因，并为实际定义的图像椭圆度。GLAM椭圆率对于任何选择的权重配置文件都具有有用的属性：加权椭圆率与椭圆图像的等照度线相同，并且在没有噪声和像素化的情况下，它始终是减少剪切的无偏估计。我们表明，矩为基础的技术，自适应或不加权，是类似于基于模型的方法，在这个意义上，它们可以被看作是不完美的椭圆形轮廓的图像拟合。由于拟合中的残差，基于矩的椭圆度估计在从观测图像推断时容易出现拟合不足的偏差。该估计基本上主要受到像素化的限制，像素化破坏了原始预视图像上的信息。我们给出了一个优化的估计的预见GLAM椭圆度和量化的无噪声图像的偏见。为了处理像素噪声，我们考虑贝叶斯方法，其中如果我们不适当地考虑我们对拟合残差的无知，则GLAM椭圆率的后验可能与真实椭圆率不一致。这种欠拟合偏差是S/N无关的，但是随着前视亮度分布和后视图像上的像素噪声的相关性或异质性而变化。此外，当从具有内在属性（尺寸、形心位置、内在形状）分布的源样本中推断恒定椭圆率或更相关的恒定剪切力时，如果使用不正确的先验知识，则会出现额外的、现在依赖于噪声的偏向低S/N。固有属性。我们讨论了这种先验偏差的起源。
In weak gravitational lensing, weighted quadrupole moments of the brightness profile in galaxy images are a common way to estimate gravitational shear. We employ general adaptive moments (GLAM) to study causes of shear bias on a fundamental level and for a practical definition of an image ellipticity. The GLAM ellipticity has useful properties for any chosen weight profile: the weighted ellipticity is identical to that of isophotes of elliptical images, and in absence of noise and pixellation it is always an unbiased estimator of reduced shear. We show that moment-based techniques, adaptive or unweighted, are similar to a model-based approach in the sense that they can be seen as imperfect fit of an elliptical profile to the image. Due to residuals in the fit, moment-based estimates of ellipticities are prone to underfitting bias when inferred from observed images. The estimation is fundamentally limited mainly by pixellation which destroys information on the original, pre-seeing image. We give an optimized estimator for the pre-seeing GLAM ellipticity and quantify its bias for noise-free images. To deal with pixel noise, we consider a Bayesian approach where the posterior of the GLAM ellipticity can be inconsistent with the true ellipticity if we do not properly account for our ignorance about fit residuals. This underfitting bias is S/N-independent but changes with the pre-seeing brightness profile and the correlation or heterogeneity of pixel noise over the post-seeing image. Furthermore, when inferring a constant ellipticity or, more relevantly, constant shear from a source sample with a distribution of intrinsic properties (sizes, centroid positions, intrinsic shapes), an additional, now noise-dependent bias arises towards low S/N if incorrect priors for the intrinsic properties are used. We discuss the origin of this prior bias.
登录
查看更多内容
DOI：
10.1111/j.1365-2966.2010.17875.x
发表时间：
2010-08
影响因子：
4.8
作者：
Peter Melchior;M. Viola;B. M. Schafer;M. Bartelmann
通讯作者：
Peter Melchior;M. Viola;B. M. Schafer;M. Bartelmann
KSB 剪切测量的偏差和修正
DOI：
10.1111/j.1365-2966.2010.17589.x
发表时间：
2011
影响因子：
4.8
作者：
Melchior;Bartelmann
通讯作者：
Bartelmann
DOI：
10.1111/j.1365-2966.2006.11315.x
发表时间：
2006-08
影响因子：
4.8
作者：
R. Massey;C. Heymans;J. Bergé;G. Bernstein;S. Bridle;D. Clowe;H. Dahle;R. Ellis;T. Erben
通讯作者：
R. Massey;C. Heymans;J. Bergé;G. Bernstein;S. Bridle;D. Clowe;H. Dahle;R. Ellis;T. Erben
影响因子：
6.5
作者：
J. Hartlap;S. Hilbert;P. Schneider;H. Hildebrandt
通讯作者：
J. Hartlap;S. Hilbert;P. Schneider;H. Hildebrandt
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