论文标题
在射手座矮星银河中发现18颗恒星，<[fe/h] <-1.45
Discovery of 18 stars with -3.10 < [Fe/H] < -1.45 in the Sagittarius dwarf galaxy
论文作者
论文摘要
一些较大的矮星系（$> 10^7 $太阳能）的早期化学演化的研究受这些系统中低金属含量已知的恒星的限制。在这里，我们介绍了18颗星的金属性和碳丰度，其金属性在$ -3.08 \ le \ le \ text {[[fe/h]} \ le -1.47 $ in sagittarius矮人球形银河系中，使用中等分辨率的光谱，使用Mageellan-Baaade Telescope的Mage Mage Specra仪。该样品使Sagittarius Dwarf Galaxy中已知的非常贫穷的恒星（[Fe/h] $ \ leq -2.0 $）的数量增加了一倍以上，并确定了系统中最早已知的极具金属贫困的星（[Fe/H] $ \ leq -3.0 $）。这些恒星被确定为使用公共，金属性敏感的光度法和来自Gaia Dr2的适当运动数据的射手座的金属贫困成员，这表明在某些矮人的某些矮星系中，这种金属贫困星的匮乏可以使用公共数据来解决目标搜索。我们发现，与银河系中的恒星相对流行相反，样品中的恒星在碳中没有增强。这些恒星的随后高分辨率光谱对于详细介绍了系统的早期化学演化至关重要。
Studies of the early chemical evolution of some larger dwarf galaxies ( $>10^7$ solar masses) are limited by the small number of stars known at low metallicities in these systems. Here we present metallicities and carbon abundances for eighteen stars with metallicities between $-3.08 \le \text{[Fe/H]} \le -1.47$ in the Sagittarius dwarf spheroidal galaxy, using medium-resolution spectra from the MagE spectrograph on the Magellan-Baade Telescope. This sample more than doubles the number of known very metal-poor stars ([Fe/H] $\leq -2.0$) in the Sagittarius dwarf galaxy, and identifies one of the first known extremely metal-poor stars ([Fe/H] $\leq -3.0$) in the system. These stars were identified as likely metal-poor members of Sagittarius using public, metallicity-sensitive photometry from SkyMapper DR1.1 and proper motion data from Gaia DR2, demonstrating that this dearth of metal-poor stars in some dwarf galaxies can be addressed with targeted searches using public data. We find that none of the stars in our sample are enhanced in carbon, in contrast to the relative prevalence of such stars in the Milky Way halo. Subsequent high-resolution spectroscopy of these stars would be key in detailing the early chemical evolution of the system.
