HIPPARCOS age metallicity relation of the solar neighbourhood disc stars
HIPPARCOS age metallicity relation of the solar neighbourhood disc stars
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DOI：
10.1051/0004-6361:20021157
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发表时间：
2002-07
影响因子：
6.5
通讯作者：
A. Ibukiyama;N. Tokyo;N. A. O. Japan
中科院分区：
文献类型：
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作者：
A. Ibukiyama;N. Tokyo;N. A. O. Japan
我们推导了1658颗太阳邻近恒星的年龄-金属丰度关系(AMR)和轨道参数，这些恒星的精确距离是由Hipparcos卫星测量的。根据轨道参数，样本恒星包括1382颗薄盘恒星、229颗厚盘恒星和47颗晕星。我们发现薄盘AMR沿着单区银河化学演化(GCE)模型有相当大的散射。薄盘恒星的轨道和金属度现在显示出明显的相互关系。即使选择具有相同轨道的恒星，沿AMR的散射也是存在的。我们研究了单区GCE模型的简单扩展，它解释了银河系中有效产额和恒星形成率的不均匀。单区GCE模型的两种扩展都不能同时考虑年龄-(Fe/H)-(Ca/Fe)关系的散布。因此，我们得出结论，沿薄盘AMR的散射是银河系形成和演化的一个基本特征。厚盘恒星的AMR结果表明，厚盘恒星的形成在8Gyr前就终止了。如Gratton等人已经报道的那样。(2000)和普罗查斯卡等人。(2000)，厚盘星比具有相同(Fe/H)的薄盘星更富钙。我们发现厚盘恒星表现出垂直的丰度梯度。AMR、垂直梯度和(Ca/Fe)-(Fe/H)关系这三个事实支持卫星矮星系的整体坍塌和/或吸积，可能是厚盘形成的情景。
We derive age-metallicity relations (AMRs) and orbital parameters for the 1658 solar neighbourhood stars to which accurate distances are measured by the HIPPARCOS satellite. The sample stars comprise 1382 thin disc stars, 229 thick disc stars, and 47 halo stars according to their orbital parameters. We find a considerable scatter for thin disc AMR along the one- zone Galactic chemical evolution (GCE) model. Orbits and metallicities of thin disc stars show now clear relation each other. The scatter along the AMR exists even if the stars with the same orbits are selected. We examine simple extension of one-zone GCE models which account for inhomogeneity in the effective yield and inhomogeneous star formation rate in the Galaxy. Both extensions of the one-zone GCE model cannot account for the scatter in age - (Fe/H) - (Ca/Fe) relation simultaneously. We conclude, therefore, that the scatter along the thin disc AMR is an essential feature in the formation and evolution of the Galaxy. The AMR for thick disc stars shows that the star formation terminated 8 Gyr ago in the thick disc. As already reported by Gratton et al. (2000) and Prochaska et al. (2000), thick disc stars are more Ca-rich than thin disc stars with the same (Fe/H). We find that thick disc stars show a vertical abundance gradient. These three facts, the AMR, vertical gradient, and (Ca/Fe)-(Fe/H) relation, support monolithic collapse and/or accretion of satellite dwarf galaxies as likely thick disc formation scenarios.