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

西蒙博士和他的团队对银河系南部的四颗矮球状卫星进行了搜索，以识别和描述极度贫金属的恒星。许多围绕银河系运行的矮星系都拥有在早期宇宙中形成的恒星。这些可能是古老恒星的元素组成是非常贫金属的（相对于我们太阳中的氢含量和元素丰度）。这些恒星的化学组成提供了最早的恒星和原星系如何形成的线索。现有的银河系晕的调查大部分已经被开采，但只有六颗恒星的铁丰度低于太阳的1/10000。众所周知，附近的矮星系包含比银河晕更多的极端贫金属恒星，因此这些是搜索和了解更多关于极端贫金属恒星的理想目标。计划在麦哲伦望远镜上使用稻盛麦哲伦区域照相机和摄谱仪（IMACS）宽视场成像仪和多物体摄谱仪对这些星系中的大约6000颗恒星进行高效观测，包括一个几乎完整的、星等有限的样本。Ca K线被用作金属丰度指标，以确定金属丰度最低的天体。这些恒星然后在高光谱分辨率下被观察，以获得对第一颗超新星的元素产额的新约束，第一颗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。Simon博士通过国家推广计划Project ASTRO与洛杉矶地区的教师合作，这是由太平洋天文学会管理的。该计划将小学到高中教师与专业和业余天文学家相匹配，将天文学带入他们的课堂。西蒙博士的新项目ASTRO活动直接关系到目前的研究，即通过宇宙时间在恒星中产生化学元素，以及它们通过超新星爆炸的扩散，使它们能够融入新的恒星，行星和生命。

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.