从宇宙剪切信号中剪切-椭圆相关的消除：测光红移误差对零化技术的影响
The removal of shear-ellipticity correlations from the cosmic shear signal: Influence of photometric redshift errors on the nulling technique
摘要：
宇宙剪切被认为是揭示暗物质和暗能量性质的最有力的探测器之一。为了充分利用其潜力，必须能够将系统效应控制在低于统计参数误差的水平。在这方面特别令人担忧的是内在的对齐，通过星系的内在椭圆率和引力剪切之间的相关性，模仿透镜效应，造成相当大的参数偏差。在早期的工作中，我们已经提出了一个调零技术，降低这个系统的权重，只利用其众所周知的红移依赖。我们评估的实用性零，光度红移信息的现实条件。对于几个简化的内在排列模型和广泛的光度红移特性，我们计算了调零前后的平均偏差。该技术的修改被引入到优化的偏置去除和最小化的信息损失的零。我们证明，所提出的版本之一是接近最佳的偏置去除方面，高品质的光度红移。为了获得良好的光度红移信息，即至少10个具有小色散的仓，灾难性异常值的可忽略部分，以及关于红移分布的精确知识，一种版本的零化能够将剪切固有椭圆率污染减少至少100倍。或者，我们描述了一个强大的零变抑制系统信号约10的光度红移配置的一个非常广泛的范围。不考虑测光红移的质量，统计功率的损失是零化所固有的，这相当于我们的品质因数减少了50%。
英文摘要：
Cosmic shear is regarded one of the most powerful probes to reveal the properties of dark matter and dark energy. To fully utilize its potential, one has to be able to control systematic effects down to below the level of the statistical parameter errors. Particularly worrisome in this respect is intrinsic alignment, causing considerable parameter biases via correlations between the intrinsic ellipticities of galaxies and the gravitational shear, which mimic lensing. In an earlier work we have proposed a nulling technique that downweights this systematic, only making use of its well-known redshift dependence. We assess the practicability of nulling, given realistic conditions on photometric redshift information. For several simplified intrinsic alignment models and a wide range of photometric redshift characteristics we calculate an average bias before and after nulling. Modifications of the technique are introduced to optimize the bias removal and minimize the information loss by nulling. We demonstrate that one of the presented versions is close to optimal in terms of bias removal, given high quality of photometric redshifts. For excellent photometric redshift information, i.e. at least 10 bins with a small dispersion, a negligible fraction of catastrophic outliers, and precise knowledge about the redshift distributions, one version of nulling is capable of reducing the shear-intrinsic ellipticity contamination by at least a factor of 100. Alternatively, we describe a robust nulling variant which suppresses the systematic signal by about 10 for a very broad range of photometric redshift configurations. Irrespective of the photometric redshift quality, a loss of statistical power is inherent to nulling, which amounts to a decrease of the order 50% in terms of our figure of merit.
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