The chemical evolution of the Galactic thick and thin disks
The chemical evolution of the Galactic thick and thin disks
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银河厚盘和薄盘的化学演化
DOI：
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发表时间：
2008
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通讯作者：
C. Chiappini
中科院分区：
文献类型：
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作者：
C. Chiappini
摘要最近的数据揭示了银河系（MW）厚盘和薄盘的丰度模式之间的明显区别，这表明这些组件中的每一个都有不同的起源。在这项工作中，我们首先回顾了薄盘形成的主要思想。从化学演化的参数，我们表明，薄盘应该形成了一个很长的时间尺度。我们还显示出明显的迹象，当地的恒星样本被来自内半径的恒星污染。然后，我们检查在这样一个模型中，为了解释厚圆盘中的可观测量，必须改变什么。我们发现，一个模型中，厚盘形成的时间尺度比薄盘短得多，星星的形成效率比薄盘大10倍左右，可以解释观测到的丰度比厚和薄盘星之间的移动几个元素。此外，厚盘和薄盘的丰度比模式缺乏分散性，这表明这两种成分都是由气体吸积而不是由较小的恒星系统合并而形成的。特别是对于厚盘，这最后一个约束成为一个强大的，如果它的金属丰度分布延伸到，至少，太阳。最后，我们简要地讨论了目前的氘丰度和目前的下降率与薄盘演化之间的相互作用。
Abstract Recent data have revealed a clear distinction between the abundance patterns of the Milky Way (MW) thick and thin disks, suggesting a different origin for each of these components. In this work we first review the main ideas on the formation of the thin disk. From chemical evolution arguments we show that the thin disk should have formed on a long timescale. We also show clear signs that the local stellar samples are contaminated by stars coming from inner radii. We then check what would have to be changed in such a model in order to explain the observables in the thick disk. We find that a model in which the thick disk forms on a much shorter timescale than thin disk and with a star formation efficiency of around a factor of 10 larger than that in the thin disk can account for the observed abundance ratio shifts of several elements between thick and thin disk stars. Moreover, the lack of scatter in the abundance ratio patterns of both the thick and thin disks suggest both components to have been formed in situ by gas accretion and not by mergers of smaller stellar systems. Especially for the thick disk, this last constraint becomes a strong one if its metallicity distribution extends to, at least, solar. Finally, we briefly discuss the interplay between present deuterium abundance and present infall rates in connection with the thin disk evolution.