The Shear TEsting Programme 2: Factors affecting high precision weak lensing analyses
The Shear TEsting Programme 2: Factors affecting high precision weak lensing analyses
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DOI：
10.1111/j.1365-2966.2006.11315.x
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发表时间：
2006-08
影响因子：
4.8
通讯作者：
R. Massey;C. Heymans;J. Bergé;G. Bernstein;S. Bridle;D. Clowe;H. Dahle;R. Ellis;T. Erben
中科院分区：
文献类型：
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作者：
R. Massey;C. Heymans;J. Bergé;G. Bernstein;S. Bridle;D. Clowe;H. Dahle;R. Ellis;T. Erben
剪切测试计划（STEP）是一个合作项目，旨在提高弱透镜测量的准确性和可靠性，为下一代宽场测量做准备。我们回顾了16个当前和新兴的剪切测量方法在一个共同的语言，并通过运行它们（盲）包含一个已知的剪切信号的模拟图像评估其性能。我们确定最成功地恢复输入参数的算法的共同特点。一个理想的目标是将他们最好的元素组合成一个最终的剪切测量方法。在这个分析中，我们通过更广泛的模拟和相对于彼此旋转的星系图像对的组合，实现了以前未达到的判别精度。这就从它们固有的椭圆度中去除了压倒性的噪音。最后，我们的模拟方法的鲁棒性是通过测试的相对校准方法对真实的数据。自第一篇STEP论文以来，弱透镜测量得到了改进。现在有几种方法始终达到2%以上的精确度，而且仍在开发中。但是，我们现在可以区分所有方法与完美性能。我们主要关注的仍然是可能出现的倍增剪切校准偏差：尤其是因为这无法用真实的数据进行内部校准。我们确定哪些星系人口负责的偏见，并通过调整模拟观测条件，我们还调查仪器和大气参数的影响。模拟点扩散函数不允许在空间上变化，以避免插值误差带来的额外混淆。我们已经分离出了几个以前未被认识到的星系形状测量方面，其中有重点的发展可以提供进一步的进展，为未来的调查所需的精度低于%的水平。这些领域包括图像像素化和星系形态演化的适当处理。忽略前一种效应会影响不同方向上剪切力的测量，导致总体上低估剪切力，从而低估物质功率谱的振幅。忽略第二种效应可能会影响剪切估计器作为星系红移函数的校准，以及透镜信号的演变，这对测量包括暗能量状态方程在内的参数至关重要。
The Shear Testing Programme (STEP) is a collaborative project to improve the accuracy and reliability of weak-lensing measurement, in preparation for the next generation of wide-field surveys. We review 16 current and emerging shear-measurement methods in a common language, and assess their performance by running them (blindly) on simulated images that contain a known shear signal. We determine the common features of algorithms that most successfully recover the input parameters. A desirable goal would be the combination of their best elements into one ultimate shear-measurement method. In this analysis, we achieve previously unattained discriminatory precision via a combination of more extensive simulations and pairs of galaxy images that have been rotated with respect to each other. That removes the otherwise overwhelming noise from their intrinsic ellipticities. Finally, the robustness of our simulation approach is confirmed by testing the relative calibration of methods on real data. Weak-lensing measurements have improved since the first STEP paper. Several methods now consistently achieve better than 2 per cent precision, and are still being developed. However, we can now distinguish all methods from perfect performance. Our main concern continues to be the potential for a multiplicative shear calibration bias: not least because this cannot be internally calibrated with real data. We determine which galaxy populations are responsible for bias and, by adjusting the simulated observing conditions, we also investigate the effects of instrumental and atmospheric parameters. The simulated point spread functions are not allowed to vary spatially, to avoid additional confusion from interpolation errors. We have isolated several previously unrecognized aspects of galaxy shape measurement, in which focused development could provide further progress towards the sub-per cent level of precision desired for future surveys. These areas include the suitable treatment of image pixellization and galaxy morphology evolution. Ignoring the former effect affects the measurement of shear in different directions, leading to an overall underestimation of shear and hence the amplitude of the matter power spectrum. Ignoring the second effect could affect the calibration of shear estimators as a function of galaxy redshift, and the evolution of the lensing signal, which will be vital to measure parameters including the dark energy equation of state.