U.S.-China Cooperative Research (Astronomy): Quasar Absorption Lines: Physical Conditions in the Early Universe

这是亚利桑那大学的吉尔·贝克泰尔和南京大学的黄克良为期两年的合作项目，目的是研究早期宇宙的物理条件。该项目由美国国家科学基金会和中国国家教委共同发起。在遥远类星体的光谱中观察到的吸收线为视线上的中间气体提供了一个强大的探测器。类星体的高亮度使天文学家能够在很远的距离研究宇宙，从而在宇宙大约是当前年龄的20%的时候研究宇宙。这是一个发生了许多重要事件的时期。星系的形成和快速的早期演化，大型结构如星系团和超星系团的崩溃的开始，以及类星体本身的快速开启。一些类星体吸收线是由正常星系星际介质中的云引起的，另一些是由正常星系星际介质中的星际云引起的，另一些星际星云可能代表了原始金属丰度的前星系或原星系物质。在任何一种情况下，类星体吸收线都提供了关于早期宇宙中物体的物理条件的直接信息，这些物体太暗，无法通过任何其他方式进行研究。这个项目的目标是分析目前可用的望远镜和仪器可以获得的类星体吸收线的最详细的光谱。光谱是在基特峰国家天文台的4米望远镜上用梯形光谱仪获得的。

This is a two.year collaborative project between Jill Bechtold of the University of Arizona and Huang Keliang of Nanjing University to study physical conditions in the early universe. The project is sponsored by NSF and the Chinese State Education Commission. The absorption lines observed in the spectra of very distant quasars provide a powerful probe of intervening gas along the line of sight. The high luminosities of quasars enable astronomers to study the Universe at great distances and hence at epochs when the Universe was about 20 percent of its current age. This was a period when many important events took place .. the formation and rapid early evolution of galaxies, the beginnings of the collapse of large structures such as clusters of galaxies and superclusters, and the rapid turn.on of quasars themselves. Some quasar absorption lines are caused by clouds in the interstellar medium of normal galaxies; others by intergalactic clouds in the interstellar medium of normal galaxies; others by intergalactic clouds that probably represent pre.galactic or proto.galactic material of primordial metal abundance. In either case, quasar absorption lines provide direct information about the physical conditions in objects in the early Universe that are too faint to study any other way. This goal of this project is to analyze the most detailed optical spectra of quasar absorption lines obtainable with currently available telescopes and instrumentation. The spectra were obtained with the echelle spectro>g.raph at the 4 meter telescope at the Kitt Peak National Observatory.