Cosmological Applications of Gravitational Lensing

当恒星、星系或星系团的引力场扭曲背景源的图像时，就会产生引力透镜，当产生多个图像时，引力透镜会“强烈”扭曲，否则就会“微弱”扭曲。引力透镜现在被视为一种工具，用于：(1)探测从黑洞到暗物质和暗能量等看不见的质量的本质；（ii）测量距离，探测宇宙的大小、形状和膨胀；（三）详细研究遥远的资料。未来使用新型望远镜的项目，如大型综合巡天望远镜和超新星加速探测器，将能够对暗物质进行详细的统计研究，并将提供对暗能量经验行为的敏感和可靠的测量。布兰福德博士的团队过去的研究结果包括：(i)证明暗物质是有效的无碰撞的，与正常的重子物质不同；（ii）利用四重成像的可变星系核对哈勃常数进行具有竞争力的精确测定；（iii）测量哈勃太空望远镜观测到的最微弱星系的群集；（iv）了解遥远类星体的分布和群集；(v)为宇宙学研究开发新的计算工具。新工作将包括：(i)对处理数千个透镜类星体的变异性数据进行更详细的规划，（ii）分析从罕见的透镜超新星和伽马射线暴中可以学到什么，（iii）更多关于星系-星系弱透镜的知识，以及可以学到的关于星系及其光晕的潜在井的知识，（iv）关于引力透镜的系统误差的新想法，特别是区分宇宙大小变化和额外质量增加的困难。(v)研究预测的特殊透镜的发生率，这些透镜可以用来测试宇宙膨胀中质量团块的理论，（vi）最大引力透镜的大小分布，以及（vii）如何利用引力透镜引起的暗淡星系聚集的畸变来确定这些星系的空间分布、性质和历史。它将极大地促进对宇宙的大小、形状和膨胀的理解，以及对宇宙主要成分——暗物质和暗能量的性质的理解。宇宙学问题继续吸引着非科学家，尤其是那些最终可能成为实践科学家或工程师的年轻人的真正兴趣。未来的大型公共数据库项目可能会改变专业天文学家和业余天文学家之间的关系。

A gravitational lens is produced when the gravitational field of a star, galaxy or cluster of galaxies distorts the images of background sources, 'strongly' when multiple images are created and 'weakly' otherwise. Gravitational lenses are now regarded as tools used to: (i) probe the nature of unseen mass, from black holes to dark matter and dark energy; (ii) measure distances and probe the size, shape and expansion of the universe; and (iii) study distant sources in exquisite detail. Future projects using new telescopes, like the Large Synoptic Survey Telescope and the SuperNova Acceleration Probe, will enable detailed, statistical studies of dark matter, and will provide a sensitive and robust measurement of the empirical behavior of dark energy. Past results from Dr. Blandford's group include: (i) demonstrating that dark matter is effectively collisionless and distinct from normal, baryonic matter (ii) a competitively accurate determination of the Hubble constant using a quadruply-imaged variable galaxy nucleus, (iii) measurement of the clustering of the faintest galaxies observed by the Hubble Space Telescope, (iv) understanding the distribution and clustering of distant quasars, and (v) developing new computational tools for cosmological investigations.The new work will include: (i) more detailed planning for handling the variability data for many thousands of lensed quasars, (ii) analyzing what can be learned from the rare lensed supernovae and gamma ray bursts, (iii) more about galaxy-galaxy weak lensing and what can be learned about the potential wells of galaxies and their halos, (iv) new ideas on systematic errors in gravitational lensing, notably the difficulty of distinguishing a change in the size of the universe from the addition of extra mass, (v) studying the predicted incidence of exceptional lenses that can be used to test the theory of how mass clumps in the expanding universe, (vi) the distribution of sizes of the largest gravitational lenses, and (vii) how to use the gravitational lensing-induced distortion of the clustering of faint galaxies to determine the distribution in space, properties, and histories of these galaxies. It will significantly advance understanding of the size, shape and expansion of the Universe and of the properties of its major constituents, dark matter and dark energy.Cosmological questions continue to attract much genuine interest among non-scientists and especially among young people who might ultimately become practicing scientists or engineers. Future projects with large publicly-accessible databases are likely to transform the relationship between professional and amateur astronomers.