Probing the Gas that Fuels Star Formation in Typical High Redshift Galaxies

探测典型高红移星系中恒星形成的气体

• 批准号: 1102683
• 负责人: Regina Jorgenson
• 金额: $ 8.3万
• 依托单位: Jorgenson, Regina A
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1102683&HistoricalAwards=false
• 关键词: Probing; Gas; Fuels; Star; Formation

Dr. Regina Jorgenson is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the University of Hawaii Institute for Astronomy (IfA). The development of large telescopes, sensitive instruments and deep surveys has allowed astronomers to detect highly star-forming galaxies back to a few hundred million years after the Big Bang (z~8). These exciting discoveries are implicitly focused on the most extreme types of star-bursting galaxies, whose light can be detected over such great distances. To develop a complete understanding of galaxy formation, these studies must be augmented by a solid understanding of typical galaxies, i.e. those galaxies that contain the majority of the baryonic matter in the universe. However, studying these typical galaxies is difficult because they are generally too faint to be directly detected in emission. Instead, these galaxies, known as the Damped Lyman alpha Systems (DLAs), have been probed in absorption against more distant background quasars.While the DLAs are known to contain the majority of the neutral gas in the universe between z = 0-5, their precise role in galaxy formation is obscured by the nature of their detection--with only a pencil beam line of sight through each galaxy--and as a result not much is known about DLA sizes, masses, morphologies, and kinematics, leaving open several important questions: (1) As the high redshift hosts of the majority of the fuel for star formation, what is their connection with star formation and the star forming galaxies? (2) What is their role in galaxy formation and evolution scenarios? and (3) While the absorption line kinematics are consistent with massive spiral galaxies at z~2, this model poses a challenge to hierarchical theories of galaxy formation, which predict most objects at z2 to have circular velocities much less than those of typical massive spirals.To understand DLAs and their connection to the star forming galaxies, this proposal aims to (1) take advantage of OSIRIS, the sensitive, new Integral Field Unit (IFU) with laser guide star adaptive optics (LGSAO) on the Keck telescope, to effectively subtract the background quasar light and directly image the H-alpha (and [N II], [O III]) emission of a sample of DLAs known to have relatively high star formation rates; and (2) utilize the ultra-high resolution spectrograph of the Subaru telescope to resolve and probe the physics of the very cold and dense velocity components that are proposed to be progenitor sites of star formation within DLA galaxies.Observations and simulations suggest that ~50% of DLAs, those with high metallicities and star formation rates as measured by their absorption profiles, are associated with bright, compact knots of star formation, whose emission can be detected with the help of LGSAO OSIRIS IFU observations. OSIRIS will be able to trace the velocity profiles and look for evidence of rotation, inflow, or outflow. Comparing [N II]/H-alpha ratio, a reliable indicator of the oxygen abundance in the ionized gas, as well as other diagnostics of star formation with those of the absorption line data will lead to a greater understanding of metallicity gradients, kinematics and star formation in the entire population of absorption line systems and provide vital constraints on simulations of galaxy formation. Analysis of ultra-high resolution spectra will complement this study with detailed understanding of the metallicity and molecule distribution in cold, dense clouds that may be gravitationally confined and represent precursor sites of star formation in DLAs.Dr. Jorgenson will also design an inquiry-based astronomy course for middle/high school students and teach the course via IfA's well-established HI STAR program. This program recruits native Hawaiians, underrepresented minorities, and students from low socioeconomic backgrounds to participate in week-long astronomy courses. The proposed course will emphasize the importance of Mauna Kea to astronomical research, vital outreach needed to maintain harmonious access to and possible further growth on the sacred mountain of Mauna Kea. In addition, at least three undergraduate students will be mentored as part of the NSF Research Experiences for Undergraduates program with particular attention paid to encouraging the participation of women and under-represented minorities in astronomy.

Regina Jorgenson博士被授予NSF天文学和天体物理学博士后奖学金，在夏威夷大学天文学研究所（IfA）开展研究和教育计划。大型望远镜、灵敏仪器和深度观测的发展，使天文学家能够探测到大爆炸（z~8）后数亿年的高度恒星形成的星系。这些令人兴奋的发现都集中在最极端类型的恒星爆发星系上，它们的光可以在如此远的距离上被探测到。为了全面了解星系的形成，这些研究必须通过对典型星系的深入了解来增强，即那些包含宇宙中大部分重子物质的星系。然而，研究这些典型的星系是困难的，因为它们通常太微弱，无法直接检测到发射。相反，这些星系，被称为阻尼莱曼阿尔法系统（DLAs），已经被探测到吸收更遥远的背景类星体。虽然DLAs已知包含宇宙中z = 0-5之间的大部分中性气体，它们在星系形成中的确切作用被它们的探测性质所掩盖--只有一束铅笔形光束穿过每个星系--因此，对DLA的大小、质量、形态和运动学知之甚少，留下了几个重要的问题：（1）作为星星形成的大部分燃料的高红移宿主，它们与星星形成和星星形成的星系有什么联系？(2)它们在星系形成和演化过程中扮演什么角色？（3）虽然吸收线运动学与z~2处的大质量旋涡星系一致，但这一模型对星系形成的分级理论提出了挑战，该理论预测z ~ 2处的大多数天体的圆速度远小于典型的大质量旋涡星系。在凯克望远镜上安装了一个新的积分场单元（IFU），带有激光引导星星自适应光学系统（LGSAO），以有效地减去背景类星体光，并直接对H-α成像（和[N II]，[O III]）发射已知具有相对高的星星形成率的DLA样品;（2）利用超斯巴鲁望远镜的高分辨率摄谱仪，用于解析和探测极冷和致密速度分量的物理学，这些速度分量被认为是DLA内星星形成的祖星观测和模拟表明，约50%的DLA，即那些具有高金属丰度和星星形成率（通过其吸收轮廓测量）的DLA，与明亮、紧凑的星星形成结有关，其发射可以在LGSAO OSIRIS IFU观测的帮助下探测到。OSIRIS将能够追踪速度剖面，并寻找旋转、流入或流出的证据。比较[N II]/H-α比，电离气体中的氧丰度的可靠指标，以及其他诊断星星形成的吸收线数据将导致更好地了解金属丰度梯度，运动学和星星形成在整个人口的吸收线系统，并提供重要的限制星系形成的模拟。超高分辨率光谱的分析将补充这项研究，详细了解冷，致密的云，可能是重力限制和代表星星形成的DLAs的前体网站的金属和分子分布。乔根森博士还将设计一个基于调查的初中/高中学生的天文学课程，并通过IfA的完善HI星星计划教授课程。该计划招募夏威夷土著人，代表性不足的少数民族和来自低社会经济背景的学生参加为期一周的天文学课程。拟议的课程将强调莫纳克亚山对天文学研究的重要性，保持和谐进入莫纳克亚圣山所需的至关重要的外联活动以及莫纳克亚圣山可能的进一步发展。此外，至少有三名本科生将作为NSF本科生研究经验计划的一部分接受指导，特别注意鼓励妇女和代表性不足的少数民族参与天文学。