Fossils of Reionization: The Search for the Most Metal-Poor Stars in the Local Group

再电离化石：寻找本星系群中最贫金属的恒星

• 批准号: 1108811
• 负责人: Joshua Simon
• 金额: $ 30.98万
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1108811&HistoricalAwards=false
• 关键词: Fossils; Reionization; Search; Most; Metal

Dr. Simon and his team undertake a search of the Milky Way's four southern dwarf spheroidal satellites to identify and characterize extremely metal-poor stars. Many of the dwarf galaxies orbiting the Milky Way host stars formed in the early universe. The elemental composition of these presumably ancient stars is very metal-poor (relative to their hydrogen content and elemental abundances in our sun). The chemical makeup of these stars holds clues how the earliest stars and the proto-galaxies formed. Existing surveys of the Milky Way halo have largely been mined but yielded only six stars with an iron abundance less than 1/10000 that of the Sun. It is known that nearby dwarf galaxies contain more extremely metal-poor stars than the galactic halo, and therefore these are ideal targets to search for and to learn more about extremely metal-poor stars. Highly efficient observations of about 6000 stars in these galaxies are planned using the Inamori Magellan Areal Camera and Spectrograph (IMACS) wide-field imager and multi-object spectrograph at the Magellan telescope, comprising a nearly complete, magnitude-limited sample. The Ca K line is used as a metallicity indicator to identify the most metal-poor objects. These stars are then observed at high spectral resolution to obtain new constraints on the elemental yields of the first supernovae, the initial mass function of the first stars, the nucleosynthesis sites responsible of producing of the heaviest elements, and the formation of the stellar halo of the Milky Way.Dr. Simon is partnering with Los Angeles-area teachers through the national outreach program Project ASTRO, which is run by the Astronomical Society of the Pacific. The program matches elementary through high school teachers with professional and amateur astronomers to bring astronomy into their classrooms. Dr. Simon's new Project ASTRO activity is directly related to the current research on the production of chemical elements in stars through cosmic time, and their dispersal by supernova explosions that allows them to be incorporated into new stars, planets, and life.

西蒙博士和他的团队对银河系南部的四颗矮球体卫星进行了搜索，以识别和表征极度缺乏金属的恒星。许多围绕银河系运行的矮星系在早期宇宙中形成了恒星。这些可能是古老恒星的元素组成非常缺乏金属（相对于它们的氢含量和我们太阳中的元素丰度）。这些恒星的化学组成为最早的恒星和原始星系的形成提供了线索。现有的对银河系光晕的调查已经在很大程度上被开采出来，但只有6颗恒星的铁含量低于太阳的万分之一。众所周知，附近的矮星系比星系晕包含更多的极贫金属恒星，因此这些是寻找和了解更多极贫金属恒星的理想目标。利用麦哲伦望远镜上的稻盛麦哲伦面相机和摄谱仪（IMACS）宽视场成像仪和多目标摄谱仪，计划对这些星系中大约6000颗恒星进行高效观测，包括一个几乎完整的、有限的样本。Ca - K线被用作金属丰度指标，以识别最缺乏金属的物体。然后用高光谱分辨率对这些恒星进行观察，以获得关于第一批超新星的元素产量、第一批恒星的初始质量函数、负责产生最重元素的核合成位点以及银河系恒星晕的形成的新限制。西蒙正在与洛杉矶地区的教师合作，通过国家外展计划ASTRO项目，该项目由太平洋天文学会运营。该项目将从小学到高中的教师与专业和业余天文学家配对，将天文学带入课堂。西蒙博士的新ASTRO项目活动与目前的研究直接相关，即通过宇宙时间在恒星中产生化学元素，以及通过超新星爆炸使它们被合并成新的恒星、行星和生命。