引力透镜信号测量及其应用

根据广义相对论，光线在宇宙中传播时会因为引力场的作用而发生偏折。遥远的背景星系在达到观测者时，其形状都会发生改变。这类形变包含了其所经历的引力场也就是宇宙中物质分布的信息，从而使得引力透镜效应成为宇宙学研究当中的重要工具。除了弱透镜效应，在星系团中心区域或是前景星系的周围，还能观测到的高阶形变，称为屈折（flexion）。这两类信号分别在大尺度和小尺度上明确地给出了宇宙物质分布的信息。但是由于背景星系内秉的形状的多样性，以及点扩散函数（PSF）的污染等原因，这些信号的提取非常困难，这也是限制引力透镜应用于未来南极KDUST及其他一系列大尺度巡天计划的瓶颈问题。本计划拟用新的方法来解决其中的几个重要问题：1）恢复、提取PSF信息；2）测量背景星系的弱透镜信号；3）推广到高阶形变（flexion）的测量；4）并最终应用于星系团的质量重建工作。这些内容将是未来南极KDUST引力透镜研究的技术储备

Gravitational lensing contains abundant information of the mass distribution in our Universe. And it is the most promising tool to constrian.the contribution of dark matter and dark energy. The mass distribution in our Univers is not homogeneous and the background galaxies are distorted when they are observed. Therefore, the distrotion in shape of galaxies tells us the information of gravitational field and then the information of the mass distribution. But this is not easy to measure. Because the image could also be distorted when they go through atmosphere and telescope, this is the so-called the point spread function(PSF) effect. The bad news is that such distortion is usually larger than that of gravitational lensing. The large-sky survey in the future will decrease the statistic error in the signal. But the PSF correction is still a problem which is still far to the end and becomes to be a big challenge not only for the people who work on weak lensing but also for whom work on strong lensing. .. We will propose a set of new methods to 1） reconstruct the PSF field 2) and then remove its effect from the observed galaxies and finally get the shear and flexion signal without bias or with acceptable bias. 3) We will also develop an new algorithm to reconstruct the mass distribution of galaxy cluster by using shear, flexion and multi-image systems. All of these topics are very important technology and science exploration for KDUST.