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arXiv 0905.3743astro-ph.SRastro-ph.GA
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斯隆数字巡天中的银河球状星团和疏散星团。II。恒星等时线的理论检验

Galactic Globular and Open Clusters in the Sloan Digital Sky Survey. II. Test of Theoretical Stellar Isochrones

Deokkeun An, Marc H. Pinsonneault, Thomas Masseron, Franck Delahaye, Jennifer A. Johnson, Donald M. Terndrup, Timothy C. Beers, Inese I. Ivans, Zeljko Ivezic

备注：
26 pages, 28 figures. Accepted for publication in ApJ. Version with high resolution figures available at http://spider.ipac.caltech.edu/~deokkeun/sdss_iso.pdf
发表信息：
Astrophys.J.700:523-544,2009
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摘要：

我们使用本系列的前一篇文章中获得的星团基准序列，对乌格里兹主序星的理论恒星模型进行了广泛的测试。我们使用耶鲁大学旋转演化代码（YREC）更新输入物理生成一组等时线，并从MARCS模型大气中获得乌格利兹的幅度和颜色。这些模型在所采用的聚类参数的误差范围内，在很宽的金属丰度范围内匹配聚类主序列。然而，我们发现在较低的主序（Teff < ~4500 K）的太阳金属丰度和以上的星系团的模型颜色有很大的差异。使用Girardi等人和Dotter等人的理论等时线，但我们的新模型通常与数据更吻合。使用我们的理论等时线，我们还获得了主序拟合距离和关闭年龄的五个关键球状星团，并证明了有能力获得这些数量的光度数据在斯隆数字巡天。特别地，我们在参数估计中利用多个颜色指数（g - r、g - i和g - z），这允许我们评估内部系统误差。我们的距离估计，与误差σ（米- M）= 0.03-0.11等的个别集群，是一致的基于依巴谷的次矮星拟合距离来自约翰逊-斯特龙格伦或测光系统。

英文摘要：

We perform an extensive test of theoretical stellar models for main-sequence stars in ugriz, using cluster fiducial sequences obtained in the previous paper of this series. We generate a set of isochrones using the Yale Rotating Evolutionary Code (YREC) with updated input physics, and derive magnitudes and colors in ugriz from MARCS model atmospheres. These models match cluster main sequences over a wide range of metallicity within the errors of the adopted cluster parameters. However, we find a large discrepancy of model colors at the lower main sequence (Teff < ~4500 K) for clusters at and above solar metallicity. We also reach similar conclusions using the theoretical isochrones of Girardi et al. and Dotter et al., but our new models are generally in better agreement with the data. Using our theoretical isochrones, we also derive main-sequence fitting distances and turn-off ages for five key globular clusters, and demonstrate the ability to derive these quantities from photometric data in the Sloan Digital Sky Survey. In particular, we exploit multiple color indices (g - r, g - i, and g - z) in the parameter estimation, which allows us to evaluate internal systematic errors. Our distance estimates, with an error of sigma(m - M) = 0.03-0.11 mag for individual clusters, are consistent with Hipparcos-based subdwarf fitting distances derived in the Johnson-Cousins or Stromgren photometric systems.

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