The Formation of Galaxies from Gas

气体形成星系

• 批准号: 0098492
• 负责人: Michael Rauch
• 金额: $ 16.18万
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-01 至 2006-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0098492&HistoricalAwards=false
• 关键词: Formation; Galaxies; Gas

ABSTRACT AST 0098492RauchHow do galaxies form? Studies show that the Quasars (QSOs) have many high redshift absorption lines from elements heavier than Helium in their spectra. Most current theories indicate that the chemical elements which give rise to these absorption lines must have been made in stars formed after the Big Bang (the so called Pop III stars). Yet when observed in quasar spectra, these absorption lines show that the metal enriched gas must be in clouds which lie between us and the QSOs.The goal of this project is to try and understand the role of this gas in galaxy formation in the early universe, at high redshift. This program is designed to complement traditional studies of galaxy formation where the emphasis has been more on the formation and fate of the stars in galaxies during the early merger or clustering process. Over the past decade, cosmological hydrodynamic computer simulations have shown that most of the early stages of galaxy formation (in particular the "dark" ones, before stars started to shine) can be observed using the absorption lines which they form in the spectra of background QSOs. The velocity structure of these lines shows infall of gas and protogalactic fragments, from the turnaround of perturbations in the intergalactic medium, as well as stellar feedback into the gas and the gasdynamics of the high redshift interstellar medium itself.The aim of this program is to use the observed properties of these low density, high ionization absorption lines to understand the relation between galaxies and gaseous inflows and outflows at high redshift. The statistics of the observed absorption systems (to be obtained from several large telescopes) will be interpreted with the help of state-of-the-art cosmological hydrodynamic -simulations. The clustering properties of metal lines on large scales will be used to trace the high redshift large scale structure at densities much lower than those probed by bright high redshift sources (e.g. radio galaxies, QSOs, Lyman-break galaxies). Absorption line profiles will be examined to determine the kinematics of the gas, and attempts will be made to identify the precise origin of the gas phases revealed by various metal absorption lines and to directly observe the infall of matter into forming galaxies. Observations of absorption systems in very close multiple lines of sight to lensed QSOs will help to quantify the density and velocity structure of the metal enriched gas near the potential wells of young galaxies. Measures of the turbulence of the gas will decide to what degree the surprisingly widespread metal enrichment of the intergalactic medium is a recent process or the result of an ancient Population III phase of starformation. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***

摘要 AST 0098492Rauch 星系是如何形成的？研究表明，类星体（QSO）的光谱中有许多来自比氦重的元素的高红移吸收线。目前大多数理论表明，产生这些吸收线的化学元素一定是在大爆炸后形成的恒星（所谓的 Pop III 恒星）中产生的。然而，当在类星体光谱中观察时，这些吸收线表明富含金属的气体一定存在于我们和 QSO 之间的云中。该项目的目标是尝试了解这种气体在早期宇宙高红移星系形成中的作用。该计划旨在补充星系形成的传统研究，其中重点更多地关注早期合并或聚类过程中星系中恒星的形成和命运。在过去的十年中，宇宙流体动力学计算机模拟表明，星系形成的大部分早期阶段（特别是恒星开始发光之前的“暗”星系）都可以使用它们在背景 QSO 光谱中形成的吸收线来观察。这些线的速度结构显示了气体和原星系碎片的坠落，来自星际介质中扰动的转变，以及对气体的恒星反馈和高红移星际介质本身的气体动力学。该计划的目的是利用这些低密度、高电离吸收线的观测特性来了解星系与气体流入和流出之间的关系 在高红移时。观测到的吸收系统的统计数据（从几个大型望远镜获得）将借助最先进的宇宙流体动力学模拟进行解释。大尺度金属线的聚类特性将用于追踪高红移大尺度结构，其密度远低于明亮的高红移源（例如射电星系、QSO、莱曼断裂星系）探测的密度。将检查吸收线轮廓以确定气体的运动学，并将尝试确定各种金属吸收线揭示的气相的精确起源，并直接观察物质落入形成的星系。在非常接近透镜 QSO 的多视线中观测吸收系统将有助于量化年轻星系势阱附近富含金属的气体的密度和速度结构。对气体湍流的测量将决定星系际介质中令人惊讶的广泛金属富集在多大程度上是最近的过程或古代第三族恒星形成阶段的结果。该项目的资金由 NSF 河外天文学和宇宙学计划 (AST/EXC) 提供。***