UNCOVERING EXTREMELY METAL-POOR STARS IN THE MILKY WAY'S ULTRAFAINT DWARF SPHEROIDAL SATELLITE GALAXIES

被引:252
作者
Kirby, Evan N. [1 ]
Simon, Joshua D. [2 ]
Geha, Marla [3 ]
Guhathakurta, Puragra [1 ]
Frebel, Anna [4 ]
机构
[1] Univ Calif Santa Cruz, Dept Astron & Astrophys, Lick Observ, Univ Calif Observ, Santa Cruz, CA 95064 USA
[2] CALTECH, Dept Astron, Pasadena, CA 91125 USA
[3] Yale Univ, Dept Astron, New Haven, CT 06520 USA
[4] Univ Texas Austin, McDonald Observ, Austin, TX 78712 USA
来源
ASTROPHYSICAL JOURNAL LETTERS | 2008年 / 685卷 / 01期
基金
美国国家科学基金会;
关键词
galaxies: abundances; galaxies: dwarf;
D O I
10.1086/592432
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present new metallicity measurements for 298 individual red giant branch stars in eight of the least luminous dwarf spheroidal galaxies (dSphs) in the Milky Way ( MW) system. Our technique is based on medium-resolution Keck DEIMOS spectroscopy coupled with spectral synthesis. We present the first spectroscopic metallicities at of stars in a dwarf galaxy, with individual stellar metallicities as low as. Because [Fe/H] < -3.0 [Fe/H] = -3.3 our [Fe/H] measurements are not tied to empirical metallicity calibrators and are sensitive to arbitrarily low metallicities, we are able to probe this extremely metal-poor regime accurately. The metallicity distribution of stars in these dSphs is similar to the MW halo at the metal-poor end. We also demonstrate that the luminosity-metallicity relation previously seen in more luminous dSph galaxies (M(v) = -13.4 to -8.8) extends smoothly down to an absolute magnitude of M(v) = -3.7. The discovery of extremely metal-poor stars in dSphs lends support to the Lambda CDM galaxy assembly paradigm wherein dwarf galaxies dissolve to form the stellar halo of the MW.
引用
收藏
页码:L43 / L46
页数:4
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