The article presents the consolidated results drawn from the chemical composition studies of Reddy et al. (2012, 2013, 2015, 2016) and Reddy & Lambert (2019), who through the high-dispersion echelle spectra ( $$R = 60000$$ R = 60000 ) of red giant members in a large sample of Galactic open clusters (OCs), derived stellar parameters and chemical abundances for 24 elements by either line equivalent widths or synthetic spectrum analyses. The focus of this article is on the issues with radial-metallicity distribution and the potential chemical tags offered by OCs. Results of these studies confirm the lack of an age–metallicity relation for OCs but argue that such a lack of trend for OCs arise from the limited coverage in metallicity compared to that of field stars which span a wide range in metallicity and age. Results demonstrate that the sample of clusters constituting a steep radial metallicity gradient of slope −0.052 ± 0.011 dex kpc $$^{-1}$$ - 1 at R $$_\mathrm{gc}<$$ gc < 12 kpc are younger than 1.5 Gyr and located close to the Galactic midplane ( $$|z|<\,$$ | z | < 0.5 kpc). Whereas the clusters describing a shallow slope of −0.015 ± 0.007 dex kpc $$^{-1}$$ - 1 at R $$_\mathrm{gc}>$$ gc > 12 kpc are relatively old with a striking spread in age and height above the midplane (0.5 $$\,<|z|<\,$$ < | z | < 2.5 kpc). Results of these studies reveal that OCs and field stars yield consistent radial metallicity gradients if the comparison is limited to samples drawn from the similar vertical heights. The computation of Galactic orbits reveals that the outer disk OCs were actually born inward of 12 kpc but the orbital eccentricity has taken them to present locations very far from their birthplaces. Published results for OCs show that the abundances of the heavy elements La, Ce, Nd and Sm but not so obviously Y and Eu vary from one cluster to another across a sample all having about the solar metallicity. For La, Ce, Nd and Sm the amplitudes of the variations at solar metallicity scale approximately with the main s -process contribution to solar system material. Consideration of published abundances of field stars suggest that such a spread in heavy element abundances is present for the thin and thick disk stars of different metallicity. This result provides an opportunity to chemically tag stars by their heavy elements and to reconstruct dissolved open clusters from the field star population.

中文翻译：

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星系化学演化和化学标记与疏散星团

本文介绍了从 Reddy 等人的化学成分研究中得出的综合结果。(2012, 2013, 2015, 2016) 和 Reddy & Lambert (2019)，他们通过大样本银河疏散星团中红巨星成员的高色散阶梯光谱 ($$R = 60000$$R = 60000) ( OCs），通过线等效宽度或合成光谱分析得出 24 种元素的恒星参数和化学丰度。本文的重点是径向金属度分布问题和 OC 提供的潜在化学标签。这些研究的结果证实了 OC 缺乏年龄 - 金属丰度的关系，但认为 OC 缺乏趋势是由于与金属丰度和年龄范围广泛的场星相比，金属丰度的覆盖范围有限。结果表明，在 R $$_\mathrm{gc}<$$ gc < 12 kpc 处构成斜率 -0.052 ± 0.011 dex kpc $$^{-1}$$ - 1 的陡峭径向金属丰度梯度的簇样本是小于 1.5 Gyr，靠近银河中平面 ($$|z|<\,$$ | z | < 0.5 kpc)。而描述 -0.015 ± 0.007 dex kpc $$^{-1}$$ - 1 在 R $$_\mathrm{gc}>$$ gc > 12 kpc 的浅斜率的集群相对较旧，在中平面上方的年龄和高度（0.5 $$\,<|z|<\,$$ < | z | < 2.5 kpc）。这些研究的结果表明，如果比较仅限于从相似垂直高度抽取的样本，则 OC 和场星会产生一致的径向金属丰度梯度。银河轨道的计算表明，外盘 OC 实际上诞生于 12 kpc 的内部，但轨道偏心率已将它们带到离它们出生地很远的位置。已发表的 OC 结果表明，重元素 La、Ce、Nd 和 Sm 的丰度，但不那么明显 Y 和 Eu 的丰度在一个样本中从一个簇变化到另一个簇，所有样本都具有太阳金属丰度。对于 La、Ce、Nd 和 Sm，太阳金属丰度的变化幅度与太阳系材料的主要 s 过程贡献大致相同。对已发表的场星丰度的考虑表明，对于不同金属丰度的薄盘星和厚盘星，存在这种重元素丰度的分布。