A New View of the Dwarf Spheroidal Satellites of the Milky Way from VLT FLAMES: Where Are the Very Metal-poor Stars?
A New View of the Dwarf Spheroidal Satellites of the Milky Way from VLT FLAMES: Where Are the Very Metal-poor Stars?
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DOI：
10.1086/509784
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发表时间：
2006-11
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通讯作者：
A. Helmi;M. Irwin;E. Tolstoy;G. Battaglia;V. Hill;P. Jablonka;K. Venn;M. Shetrone;B. Letarte;N. Arimoto;Tom Abel;P. Francois;P. Francois;A. Kaufer;F. Primas;K. Sadakane;T. Szeifert
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作者：
A. Helmi;M. Irwin;E. Tolstoy;G. Battaglia;V. Hill;P. Jablonka;K. Venn;M. Shetrone;B. Letarte;N. Arimoto;Tom Abel;P. Francois;P. Francois;A. Kaufer;F. Primas;K. Sadakane;T. Szeifert
作为矮星系丰度和径向速度团队（DART）计划的一部分，我们测量了附近四个矮球状星系（dSph）中大样本恒星的金属丰度：Sculptor，Sextans，Fornax和Carina。这些星系中的低平均金属丰度和非常古老的恒星群体的存在支持了它们是早期宇宙化石的观点。然而，与天真的期望相反，我们发现在所有四个系统中，金属丰度低于[Fe/H] ~ -3 dex的恒星都非常缺乏。这表明，在这些系统中，组成恒星的气体在形成之前就已经均匀富集。此外，dSph金属丰度分布的贫金属尾部与银河系晕的贫金属尾部明显不同。这些发现表明，即使在最早的时代，附近dSph的祖先似乎也与银河系的构建块有着根本的不同。
As part of the Dwarf galaxies Abundances and Radial-velocities Team (DART) program, we have measured the metallicities of a large sample of stars in four nearby dwarf spheroidal galaxies (dSph's): Sculptor, Sextans, Fornax, and Carina. The low mean metal abundances and the presence of very old stellar populations in these galaxies have supported the view that they are fossils from the early universe. However, contrary to naive expectations, we find a significant lack of stars with metallicities below [Fe/H] ~ -3 dex in all four systems. This suggests that the gas that made up the stars in these systems had been uniformly enriched prior to their formation. Furthermore, the metal-poor tail of the dSph metallicity distribution is significantly different from that of the Galactic halo. These findings show that the progenitors of nearby dSph's appear to have been fundamentally different from the building blocks of the Milky Way, even at the earliest epochs.