老年疏散星团的金属丰度及银盘金属丰度梯度演化研究

Metallicity of Old Open Star Clusters and Study on the Evolution of Metallicity Gradient of Galactic Disk

疏散星团是探究银河系结构与演化的良好示踪体,一直以来颇受关注.之前关于疏散星团的研究中,仅有一小部分疏散星团有金属丰度参数,而且,金属丰度的测量,是基于不同质量的观测数据,采用了不同的方法.收集了一个年龄大于2 Gyr的老年疏散星团样本,通过整理这些星团成员星的金属丰度数据,一方面,以星团NGC 2682为例,对比了不同光谱巡天项目给出的星团成员星金属丰度的系统差异;另一方面,计算了星团成员星金属丰度的平均值和中位值,作为该疏散星团的金属丰度推荐值.此外,还利用该样本探究了银盘径向金属丰度梯度随时间的演化,结果表明,早期银盘有着更加陡峭的径向金属丰度梯度,随着演化时间的增加,银盘径向金属丰度梯度逐渐趋于平缓,为银盘化学演化模型提供了更加严格的观测约束.

Open clusters are good tracers for the study of the structure and evolution of the Milky Way.Previous studies of open clusters have shown that only a small number of open clusters have metallicity measurements.Moreover,these measurements based on different qualities of observed data,using different methods.In this paper,we collected a sample of an elderly open cluster older than 2 Gyr by collating the metallicity data of these cluster members.On the one hand,the systematic errors of metallicity of members given by different spectral survey projects are compared as the example of NGC 2682.On the other hand,the mean and median values of metallicity of the members are calculated as the recommended values of metallicity of the open cluster.In addition,the evolution of the radial metallicity gradient of the disk with time was investigated using this sample.The results show that the radial metallicity gradient of the disk is steeper in the early stage,and gradually becomes flat with the increase of evolution time,which provides a more strict observation constraint for the chemical evolution model of the disk.