Ages and metallicities of star clusters: New calibrations and diagnostic diagrams from visible integrated spectra
Ages and metallicities of star clusters: New calibrations and diagnostic diagrams from visible integrated spectra
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DOI：
10.1051/0004-6361:20041560
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发表时间：
2004-09
影响因子：
6.5
通讯作者：
J. F. C. Santos;A. E. P. ICEx-UFMG;Brazil.;IAFE-UBA;Argentina.
中科院分区：
文献类型：
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作者：
J. F. C. Santos;A. E. P. ICEx-UFMG;Brazil.;IAFE-UBA;Argentina.
我们展示了星团年龄和金属丰度的均匀尺度，从非常年轻的天体，到中年的天体，再到已知最古老的星团。所有选择的星团都有可见光范围内的综合光谱，以及它们的年龄和金属丰度的可靠测定。从这些光谱中均匀地测量了K - Ca - II、G波段（CH）和Mg - I金属以及Hδ、H γ和Hβ Balmer谱线的等效宽度。对这些EWs的分析表明，对于年龄小于10 Gyr的天体，金属和Balmer H线的EWs和分别是星团年龄的良好指标，而对于年龄大于10 Gyr的天体，前者对星团金属丰度也很敏感。我们提出了一种迭代方法，通过使用两个新的诊断图和基于上述EW和的年龄校准来估计簇年龄。对于年龄大于10 Gyr的集群，我们还提供校准以获得其总体金属含量。
We present homogeneous scales of ages and metallicities for star clusters from very young objects, through intermediate-age ones up to the oldest known clusters. All the selected clusters have integrated spectra in the visible range, as well as reliable determinations of their ages and metallicities. From these spectra equivalent widths (EWs) of K Ca II, G band (CH) and Mg I metallic, and Hδ ,H γ and Hβ Balmer lines have been measured homogeneously. The analysis of these EWs shows that the EW sums of the metallic and Balmer H lines, separately, are good indicators of cluster age for objects younger than 10 Gyr, and that the former is also sensitive to cluster metallicity for ages greater than 10 Gyr. We propose an iterative procedure for estimating cluster ages by employing two new diagnostic diagrams and age calibrations based on the above EW sums. For clusters older than 10 Gyr, we also provide a calibration to derive their overall metal contents.