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的四颗南矮星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都是在早期宇宙中形成的恒星。据推测，这些古老恒星的元素组成非常贫金属(相对于它们在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始星系如何形成的线索。现有的对银河系晕的调查基本上都是开采的，但只有6颗恒星的铁丰度不到太阳的1/10000。众所周知，附近的矮星系含有比银晕更多的极度贫金属星，因此这些恒星是寻找和更多了解极度贫金属星的理想目标。计划使用稻盛麦哲伦区域相机和光谱仪(IMACS)广域成像仪和麦哲伦望远镜的多目标光谱仪对这些星系中的约6000颗恒星进行高效观测，其中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，以识别最贫金属化的物体。然后在高光谱分辨率下对这些恒星进行观测，以获得对第一批超新星的元素产额、第一批恒星的初始质量函数、负责产生最重元素的核合成点以及银河系恒星晕形成的新限制。西蒙正在与洛杉矶地区的教师合作，通过由太平洋天文学会运营的全国推广计划项目ASTRO。该计划将小学到高中的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ASTRO项目活动与目前的研究直接相关，这些研究涉及恒星中化学元素在宇宙时间中的产生，以及它们通过超新星爆炸的扩散，从而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.