Observational Cosmology by Observing Gravitational Lensing

9624592摘要-伯恩斯坦主宰宇宙的暗物质不会发出可探测到的辐射，但会由于经过的光线的引力偏转而扭曲背景物体的图像。研究计划是测量这些“弱引力透镜”效应，以确定星系团的真实形状和当今宇宙中质量波动的光谱。这些微弱的透镜扭曲现在被用来测量几个丰富星系团内部的质量分布。10个星系团的质量分布将被测量到更大的半径。这是非常有意义的，因为理论N体模拟表明，星系团的形状和轮廓对宇宙密度参数欧米茄的值和暗物质粒子的性质很敏感。一个特别有趣的例子是弱星系团0957+561，它包含一个已知时间延迟的多重成像类星体。通过映射星团质量，该透镜的建模将得到改进，并将获得哈勃常数的改进值。要及时完成这些观测，需要使用望远镜上的电荷耦合器件(电荷耦合器件)马赛克相机，以获得良好的视力。密歇根-达特茅斯-麻省理工学院(MDM)2.4米望远镜的CCD相机将被建造。现在已经初步探测到天空中随机部分的弱引力透镜。将对数百万个场星系的弱引力扭曲进行测量，这些测量结果将提供下列明确的定量测量数据：8 MPC尺度上的质量波动强度，其中线性微扰理论成立，这些波动与早期宇宙的量子过程直接相关；在较小区域内的功率谱斜率，这将区别于目前的结构形成竞争模型；100KPC尺度的功率谱，在那里将找到星系形成和暗物质晕性质的线索；以及这些结构在宇宙历史最后三分之一的增长率。只有在使用具有极大吞吐量的成像设备时，这些测量才是可行的。大面积CCD(LACCD)马赛克相机将完成并安装在智利的Cerro Tololo美洲天文台(CTIO)4米望远镜上，比那里的任何其他仪器都有更大的吞吐量。根据这笔赠款完成的两台相机(MDM和CTIO)将成为设施仪器，并可供其他天文学家使用。完成的仪器还将用于加强密歇根大学学生的教育。博士生将获得以前没有的仪器经验，选择的本科天文学专业的学生将在密歇根和天文台从事仪器工作。针对非理科专业本科生的入门课程将进行改革，重点是通过引入更多现代实验室练习和改进课堂演示来提高学生的视觉和解决问题的能力。这项计划的结果，以及其他天文学系成员目前的结果，将通过每月一次的全彩色俱乐部邮寄方式传达给密歇根州的高中科学教师和学生。

AST 9624592 Abstract - Bernstein The dark matter which dominates the Universe does not emit detectable radiation, but does distort images of background objects by the gravitational deflection of the passing light rays. The research plan is to measure these "weak gravitational lensing" effects to determine the true shapes of galaxy clusters and the spectrum of the mass fluctuations in the present-day Universe. These weak lensing distortions are now being used to measure the mass distributions of the inner parts of a few rich clusters of galaxies. The mass profiles of 10 clusters of galaxies will be measured to a larger radius. This is of great interest since theoretical N-body simulations show that cluster shapes and profiles are sensitive to the value of the cosmological density parameter Omega, and to the nature of the dark matter particles. A particularly interesting case is the weak cluster 0957+561, which contains a multiply-imaged quasar with known time delay. By mapping the cluster mass, the modeling of this lens will be improved and an improved value for the Hubble constant will be obtained. The timely completion of these observations requires the use of a Charged Coupled Device (CCD) mosaic camera on a telescope with good seeing. A CCD camera for the Michigan-Dartmouth-MIT (MDM) 2.4m telescope will be constructed. Weak gravitations lensing in random parts of the sky has now been tentatively detected. The weak gravitational distortions of several million field galaxies will be measured, the results from these measurements will provide unambiguous quantitative measurements of: the strength of mass fluctuations on 8 Mpc scales, where linear perturbation theory holds and the fluctuations are directly related to quantum processes in the early Universe; the slope of the power spectrum in the in smaller regions, which distinguishes between present rival models of the structure formation; the power spectrum on 100 kpc scales, where clues to the nature of galaxy formation and dark matter halos will be found; and the growth rate of these structures over the last third of the history of the Universe. These measurements are only feasible if imaging devices with extremely large throughput are used. The Large Area CCD (LACCD) mosaic camera will be completed and mounted on the Cerro Tololo Interamerican Observatory (CTIO) 4m telescope in Chile, giving larger throughput than any other instrument there. Both cameras (at MDM and CTIO) to be completed under this grant will become facility instruments and made available to other astronomers. The completed instruments will also be used to enhance the education of students at the University of Michigan. Ph. D. students will obtain previously unavailable instrumentation experience, and selected undergraduate astronomy majors will work with instruments in Michigan and at observatory sites. The introductory courses for non-science major undergraduates will be revamped, with an emphasis on improving the students' visualization and problem-solving abilities by introducing more modern laboratory exercises and improved classroom demonstrations. The results of this program, and current results by other Astronomy Department members, will be communicated to high school science teachers and students throughout the State of Michigan via a monthly full-color "Image-of-the-Month" club mailing.