Investigation of Gas in Protogalaxies

本提案的目标是研究类星体光谱中阻尼莱曼α吸收系统的性质和含义。PI的早期工作表明，Ly-alpha系统是大多数正常星系的气态祖先，其运动学和电离水平表明吸收在移动中，可能是合并，而不是光滑的盘。PI已经启动了一个数值密集的模拟程序，以检查观测结果与宇宙学参数之间的一致性。该计划的目标是找到并观察典型的当前星系的祖先，即，原星系目前的理论（例如冷暗物质宇宙学（CDM））预测，大多数原星系的质量比现在的星系小得多。因此，由非常遥远的原星系发出的星光太微弱，无法用传统技术探测到。相比之下，本提案中讨论的中性气体巡天能够探测到低质量的天体。由于当前星系中的恒星在过去100亿年中是由星际气体形成的，因此原星系中的大多数普通物质肯定是气体。我们探测到的气体吸收了更遥远的类星体发出的明亮光线。气态原星系的主要特征是氢莱曼-α谱线的强吸收。原则上，我们可以探测到低质量的物体，因为气体的吸收强度对原星系质量的变化不敏感。在这项工作中，PI将使用两台凯克10米望远镜来测试CDM的预测，研究中性和电离气体的速度结构，以确定气体运动是否由旋转圆盘或其他机制产生。测量重元素的丰度，以追踪宇宙时间尺度上星系的化学富集。并寻找与吸收气体有关的星系发出的星光。这些观测结果将与CDM宇宙学中阻尼莱曼-α系统形成的数值模拟进行比较。该项目的资金由美国国家科学基金会的河外天文宇宙学计划（AST/EXC）提供。

AST- 0071257WolfeThe goals of this proposal are to study the properties and implications of the damped Lyman-alpha absorption systems seen in quasar spectra. The PI's earlier work suggests that Ly-alpha systems are the gaseous progenitors of most normal galaxies with kinematics and ionization levels which indicate absorption in moving, presumably merging, clumps rather than smooth disks. The PI has started a numerically-intensive simulation program to examine consistency between the observations and cosmological parameters.The object of this proposal is to find and observe the ancestors of typical current galaxies; i.e., protogalaxies. Current theories, (for example, cold dark matter cosmologies (CDM)), predict that most protogalaxies were much less massive than current galaxies. Thus, the starlight emitted by exceedingly distant protogalaxies is too faint to detect by conventional techniques. By contrast the surveys for neutral gas discussed in this proposal are capable of detecting low-mass objects.Since stars in current galaxies have formed out of interstellar gas for the past 10 billion years, most of the ordinary matter in protogalaxies must have been gas. We detect the gas in absorption against the bright light emitted by even more distant quasars. The principal signature of gaseous protogalaxies is strong absorption in the hydrogen Lyman - alpha line. In principle we can detect low-mass objects since the absorption strength of the gas is insensitive to variations of the mass of the protogalaxy. In this work, the PIs will use the two Keck 10 m telescopes to test predictions of CDM, studying the velocity structure of the neutral and ionized gas to determine whether gas motions are generated by rotating disks or some other mechanism. and measuring the abundance of heavy elements in order to trace chemical enrichment of galaxies over cosmic time scales. and searching for emission of starlight from galaxies associated with the absorbing gas. These observations will be compared with numerical simulations of the formation of damped Lyman - alpha systems in CDM cosmologies. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***