New Vistas in Weak Lensing

光线在经过大质量物体时会被引力弯曲，这是爱因斯坦最早预测的。当天体质量足够大时，比如整个星系，光线就会弯曲到足以聚焦的程度，形成所谓的“引力透镜”。自爱因斯坦的预言以来，引力透镜的研究已经取得了巨大的发展，事实上，引力透镜是我们知道“暗物质”存在的主要原因之一。尽管所有的光都受到这种影响，但到目前为止，只有两种光源被用来研究引力透镜：来自单个星系的光，以及大爆炸留下的光，称为宇宙微波背景（CMB）。这个项目将大大增加引力透镜研究的领域。特别是，它将在目前观察到的两个透镜场的基础上增加三个不同的新透镜场。 这些是（1）星系际空间中的气体云（我们可以在三维空间中看到），（2）星系群和星系团，以及（3）从天空不同方向看到的CMB光测量的时间延迟场。最后一个，宇宙微波背景辐射的时间延迟，是由于光在通过引力透镜时速度减慢，因此当透镜位于观察者和可观察宇宙的边缘（宇宙微波背景辐射的起源）之间时，光会稍后到达观察者。 该项目旨在了解这些新领域背后的理论，如何最好地测量透镜效应以及如何使用它们来制作宇宙中暗物质的精确地图。 这些与宇宙的长度尺度和内容有关的概念也将通过该项目传播给小学到高中的学生。这将通过教育视频游戏来完成，包括开发“我的世界”天文学课程计划，以及探索类星体和星系际空间以及宇宙化学成分的计算机模型。弱引力透镜可以说是绘制宇宙黑暗面的最佳方法。数十亿美元级的调查和卫星将使用由透镜引起的星系形状扭曲（星系切变）来做到这一点。最近采用的宇宙微波背景（CMB）的透镜作为宇宙学探测已经显示出不同的透镜畸变示踪剂的优势，具有不同的强度和系统误差。然而，这些对弱透镜效应的观察仅仅是一个开始，任何背景光源都会经历同样的扭曲，还有丰富的现象学有待发现。这项工作将扩大使用透镜各向异性的集群到三个新的领域，莱曼α森林，星系相关函数，和CMB的时间延迟。没有一个依赖于星系形状的测量，这使得精确的星系切变测定变得困难，但是两个可以用当前的数据测量到很高的意义，一个对未来的调查有潜在的影响。PI和Co-I已经就这些主题提出了一些初步想法，现在是时候共同努力释放其全部潜力了。该项目将制定估计量，从原始数据中导出透镜参数，并利用现实的模拟数据集，在存在非线性和非高斯性的情况下对其进行测试和开发。这些估计数将应用于星系间介质和星系分布调查的数据。物质波动幅度的统计误差预计在百分之几的水平，但真正的收益将是不同的系统误差剪切和新的方式的数据可以探测宇宙学。 这些技术将为测量中微子质量和结构演化提供一条新的途径。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Light rays are bent by gravity as they move past massive objects, in a way that was first predicted by Einstein. When astronomical objects are massive enough, such as whole galaxies, then the light bends enough that it can be brought to a focus, creating what is known as a "gravitational lens". Since Einstein's prediction, the study of gravitational lensing has grown enormously, and indeed gravitational lensing is one of the main reasons that we know that "dark matter" exists. Even though all light is affected in this way, so far only two sources of light have ever been used to study gravitational lensing: light from individual galaxies, and the left over light from the Big Bang, known as the Cosmic Microwave Background (CMB). This project will greatly increase the domain over which gravitational lensing is studied. In particular it will add three different new lensed fields to the two currently observed. These are (1) clouds of gas in intergalactic space (which we can view in three dimensions), (2) groups and clusters of galaxies, and (3) the field of time delays measured from CMB light seen in different directions on the sky. The last one, CMB time delay, is caused by the fact that light slows down as it passes through a gravitational lens, so that light arrives at an observer later when a lens is between them and the edge of the observable universe (where the CMB originates). The project aims to lead to an understanding of the theory behind these new fields, how best to measure the lensing effects and how to use them to make accurate maps of the dark matter in the Universe. These concepts, related to the length scales and contents of the cosmos will also be spread by the project to elementary through high school students. This will be done with educational video games, including development of "Minecraft" astronomy lesson plans, and explorable computer models of quasars and intergalactic space and the chemical constituents of the Universe.Weak gravitational lensing is arguably the best way to map out the dark side of the Universe. Billion dollar class surveys and satellites will use distortions of galaxy shapes (galaxy shear) caused by lensing to do this. The more recent adoption of lensing of the Cosmic Microwave Background (CMB) as a cosmological probe has shown the advantages of a different tracer of lensing distortions, with different strengths and systematic errors. These observations of weak lensing are only the beginning, however - any background light sources will undergo the same distortions and there is a rich phenomenology yet to be discovered. The work will expand the use of lensing anisotropies of clustering to three new areas, the Lyman-alpha forest, the galaxy correlation function, and CMB time delay. None relies on measurement of galaxy shapes which can make precise galaxy shear determinations difficult, but two can be measured to high significance with current data and one has potential implications for future surveys. The PI and Co-I have developed some of the first ideas on these topics, and the time is ripe for a concerted effort to unlock their full potential. The project will formulate estimators to derive lens parameters from raw data, and make use of realistic simulated datasets to test and develop them in the presence of non-linearities and non-Gaussianity. These estimators will be applied to data from surveys of the intergalactic medium and the distribution of galaxies. Statistical errors on the matter fluctuation amplitude at the few percent level are expected, but the true gains will be in the differing systematic errors to shear and the new ways the data can probe cosmology. These techniques will offer a new route to measuring the neutrino mass and the evolution of structure.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.