Cosmological Tests with Weak Gravitational Lensing Surveys

Bernstein博士，Jain博士和他们的团队将开发和测试软件，从大型成像调查中提取弱引力透镜的信息。弱透镜效应指的是遥远星系的图像中出现的微小畸变，这种畸变是由于光被沿着光路的物质团块的引力所弯曲而产生的。因此，这项工作提供了关于质量如何在最大的宇宙尺度上分布的信息。该小组将探索更好的技术来测量星系图像的形状。他们将改进用于确定点扩散函数（PSF，用于测量地球大气和望远镜光学对图像的扭曲效应）和测量星系颜色以及从这些颜色推断出的距离的管道软件的性能，即使不同颜色的图像之间的PSF不同。他们将开发一种方法，在考虑重要的系统误差，并利用调查图像中所有可用信息的同时，找到最适合给定观测集合的宇宙学参数组合，但在计算上仍是可行的。最后，该团队将探索透镜测量的最佳组合，以测试修正引力理论，该理论已被提出作为暗能量的替代品，以解释观测到的宇宙加速。开发的软件将在主调查开始之前用暗能量调查的委托数据进行测试。两名研究生将在参与研究时接受培训。在测量星系形状、颜色和估计距离方面提出的改进将普遍适用于天文成像调查，并且应该对引力透镜以外的研究有用。

Dr Bernstein, Dr Jain and their team will develop and test software to extract information on weak gravitational lensing from large imaging surveys. Weak lensing refers to the small distortions in the images of distant galaxies that result when its light is bent by the gravitational pull of clumps of matter that lie along the light path. This work therefore gives information about how mass is distributed on the largest cosmic scales. The team will explore better techniques for measuring the shapes of galaxy images. They will improve the performance of pipeline software for determining the point spread function (PSF, which measures the distorting effect of the Earth's atmosphere and the telescope optics on the images), and for measuring galaxy colors, and the distances inferred from those colors, even when the PSF differs between images in different colors. They will develop a method to find the combination of cosmological parameters that best fits a given set of such observations, while taking account of important systematic errors, and making use of all the available information in the survey images, but remaining computationally feasible. Finally, the team will explore the best combination of lensing measurements to test theories of modified gravity, which have been proposed as alternatives to dark energy in explaining the observed cosmic acceleration. The software developed will be tested with commissioning data from the Dark Energy Survey prior to the start of the main survey. Two graduate students will be trained as they participate in the research. The proposed improvements in measurements of galaxy shape, color and estimated distances will be generally applicable to astronomical imaging surveys, and should be useful for studies beyond gravitational lensing.