通过零化技术从宇宙剪切信号中去除剪切-椭圆相关
The removal of shear-ellipticity correlations from the cosmic shear signal via nulling techniques
摘要：
为了使宇宙切变成为一种高精度的天文工具，必须消除系统对其信号的影响，其中最重要的影响之一是引力切变与源星系内禀椭圆率之间的相关性。由于目前的模型的内在对齐的粗糙，我们已经开发了一个独立的模型，纯粹的几何方法来消除剪切椭圆相关。我们消除的贡献层析宇宙剪切信号，可能会受到污染的剪切椭圆相关性，利用这些相关性的特征依赖红移。通过引入一个适当选择的权重函数的透镜效应的效率，零信号源于一定的距离，新的二阶措施的宇宙剪切，自由的内在对齐，可以构建。这种归零技术和随后退化的宇宙学参数的约束所引起的信息的损失被量化的可能性分析。关于最优权函数的构造，所有考虑的方法之间取得了良好的一致性。对于分为20个红移箱的调查，我们发现，可信区域的面积增加了20%至约50%的应用程序后，归零，这取决于宇宙学参数考虑。我们证明，由于优化的权重函数，几乎所有的信息都包含在一个小的子集的新的二阶措施。在保守假设下，使用比20个小得多的红移仓进行置零会大大降低参数约束，强调需要详细的红移信息。
英文摘要：
To render cosmic shear an astronomical tool of high precision, it is essential to eliminate systematic effects upon its signal, one of the most significant ones being correlations between the gravitational shear and the intrinsic ellipticity of source galaxies. Because of the crudeness of current models of intrinsic alignment, we have developed a model-independent, purely geometrical method to remove shear-ellipticity correlations. We eliminate the contributions to a tomographic cosmic shear signal that may be subject to contamination by shear-ellipticity correlations, making use of the characteristic dependence of these correlations on redshift. By introducing an appropriately chosen weight function to the lensing efficiency that nulls signals stemming from certain distances, new second-order measures of cosmic shear, free of intrinsic alignment, can be constructed. The loss of information induced by this nulling technique and the subsequent degradation of constraints on cosmological parameters is quantified in a likelihood analysis. Concerning the construction of optimal weight functions, good agreement is achieved between all approaches considered. For a survey divided into 20 redshift bins we find that the area of credible regions increases by 20% up to about 50% after the application of nulling, depending on the cosmological parameters considered. We demonstrate that due to an optimization of the weight functions nearly all information is contained in a small subset of the new second-order measures. The use of a significantly smaller number of redshift bins than 20 for the nulling considerably degrades parameter constraints under conservative assumptions, emphasizing the need for detailed redshift information.
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