暗物质在天球上的弱引力透镜映射
Mapping dark matter on the celestial sphere with weak gravitational lensing
摘要：
综合物质分布的会聚图是弱引力透镜测量的一个关键科学成果。迄今为止，已经使用天球的平面近似来执行恢复收敛图。然而，随着暗能量实验所覆盖的天空面积的增加，如欧几里得，大型综合巡天望远镜（LSST）和宽视场红外巡天望远镜（WFIRST），这种假设将不再有效。我们恢复收敛领域的天球使用扩展的凯撒-斯奎尔斯估计的球形设置。通过仿真，我们研究了平面近似引入的误差。此外，我们研究如何最好地恢复收敛地图的平面设置，考虑各种不同的投影和定义的本地旋转时，需要投影自旋场，如宇宙剪切。对于未来巡天的典型天空覆盖范围，投影效应引入的误差可以达到百分之几十，在某些情况下超过50%。球极投影是最有效的平面投影，它是保角的，因此保持了局部角度。在任何情况下，这些错误可以完全避免恢复收敛领域直接在天球。我们应用球形凯撒-斯奎尔斯质量映射方法提出的公共暗能量调查（DES）的科学验证数据直接恢复收敛地图上的天球。
英文摘要：
Convergence maps of the integrated matter distribution are a key science result from weak gravitational lensing surveys. To date, recovering convergence maps has been performed using a planar approximation of the celestial sphere. However, with the increasing area of sky covered by dark energy experiments, such as Euclid, the Large Synoptic Survey Telescope (LSST), and the Wide Field Infrared Survey Telescope (WFIRST), this assumption will no longer be valid. We recover convergence fields on the celestial sphere using an extension of the Kaiser-Squires estimator to the spherical setting. Through simulations we study the error introduced by planar approximations. Moreover, we examine how best to recover convergence maps in the planar setting, considering a variety of different projections and defining the local rotations that are required when projecting spin fields such as cosmic shear. For the sky coverages typical of future surveys, errors introduced by projection effects can be of order tens of percent, exceeding 50% in some cases. The stereographic projection, which is conformal and so preserves local angles, is the most effective planar projection. In any case, these errors can be avoided entirely by recovering convergence fields directly on the celestial sphere. We apply the spherical Kaiser-Squires mass-mapping method presented to the public Dark Energy Survey (DES) science verification data to recover convergence maps directly on the celestial sphere.
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