Cosmic Flexion

爱因斯坦相对论的一个伟大预言是，光可以被恒星和星系等巨大的天体物理物体弯曲。这种现象被称为引力透镜，它会导致相对较近的物体出现拉伸和扭曲，就像通过放大镜的边缘看到的那样。通过解释这些扭曲，就有可能找出产生透镜的物质的位置。德雷塞尔大学的科学家们旨在通过观察大约1亿个星系的形状来测量宇宙中暗物质的质量分布。由于彼此靠近的星系也会经历类似的扭曲，因此可以推断出暗物质的真实位置和分布。从科学上讲，这项工作具有广泛的影响，因为它处理了物质如何在小尺度上进化的最基本问题。作为该项目的一部分，该团队还将针对费城高中生开发一所宇宙学暑期学校。这项工作涉及使用暗能量测量（DES）从大尺度结构到约束差的非线性结构的第一次宇宙弯曲测量。这种方法以宇宙剪切测量为模型，其中星系对的透镜信号是相关的。引力弯曲（图像的“弧度”）等于暗物质密度场的梯度，对小尺度的扰动特别敏感。宇宙剪切测量结构的尺度从2角分到几度。相比之下，大尺度结构的宇宙屈曲分析可以产生2 ~ 20弧秒的非线性功率谱约束，对应于几十千秒尺度。该团队还将测量弯曲-剪切相关函数，它将产生从几弧秒到10弧分的信号，弥合宇宙剪切和弯曲两种机制之间的差距。最后，相同的数据集和约简可以并且将被应用于估计单个星系-星系透镜信号，并产生对星系质量函数的约束。除了提供对小尺度宇宙结构的直接估计外，研究小组还将利用他们的专业知识开发可供更广泛社区使用的工具。该奖项反映了美国国家科学基金会的法定使命，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。

One of the great predictions of Einstein's Theory of Relativity is that light can be bent by massive, astrophysical objects like stars and galaxies. This phenomenon, known as gravitational lensing, can cause relatively nearby objects to appear stretched and distorted, as if seen through the edges of a magnifying glass. By interpreting those distortions, it is possible to figure out the location of matter creating the lensing. Scientists at Drexel University aim to measure the mass distribution of dark matter in the universe by looking at the shapes of approximately 100 million galaxies. Since galaxies that are near one another also experience similar distortions, the true location and distribution of dark matter can be inferred. Scientifically, this work has a broad impact as it deals with the most fundamental questions of how matter evolves on small scales. As part of this project, the team will also develop a Cosmology Summer School aimed at Philadelphia high school students.This work involves the first measurement of Cosmic Flexion from large-scale structure, well into the poorly constrained, nonlinear regime, using the Dark Energy Survey (DES). This approach is modeled on cosmic shear measurements in which the lensing signals of pairs of galaxies are correlated. Gravitational flexion (the ``arciness'' of an image) is equal to the gradient of the dark matter density field and is particularly sensitive to small scale perturbations. Cosmic shear measures structure on scales from 2 arcminutes up to several degrees. By comparison, cosmic flexion analysis of large-scale structure can produce constraints on the nonlinear power spectrum from 2 to 20 arcseconds, corresponding to the tens of kilosparsecs scale. The team will also measure flexion-shear correlation functions, which will produce signals ranging from several arcseconds to 10 arcminutes, bridging the gap between the two regimes of cosmic shear and flexion. Finally, the same dataset and reduction can and will be applied to estimate individual galaxy-galaxy lensing signals and produce constraints on galaxy mass functions.The research team will utilize their expertise to develop tools which can be used by the broader community, in addition to providing direct estimates of small-scale cosmic 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.