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Membership determination is the key-important step to study open clusters, which can directly in?uence on the estimation of open clusters’ physical parameters. DBSCAN (Density Based Spatial Clustering of Applications with Noise) is a density-based clustering algorithm in data mining techniques. In this paper the DBSCAN algorithm has been used for the ?rst time to make the membership determination of the open clusters NGC 6791 and M 67 (NGC 2682). Our results indicate that the DBSCAN algorithm can effectively eliminate the contamination of ?eld stars. The obtained member stars of NGC 6791 exhibit clearly a doubled main-sequence structure in the color-magnitude diagram, implying that NGC 6791 may have a more complicated history of star formation and evolution. The clustering analysis of M67 indicates the presence of mass segregation, and the distinct relative motion between the central part and the outer part of the cluster. These results demonstrate that the DBSCAN algorithm is an effective method of membership determination, and that it has some advantages superior to the conventional kinematic method. 相似文献
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利用斯隆数字巡天（SDSS）第8次释放数据（DR8）的恒星光谱数据及2MASS（Two Micro All Sky Survey）近红外点源测光数据研究著名的疏散星团NGC 6791,得到该星团的视向速度与金属丰度分别为Vr=-46.4±0.2 km·s-1和[Fe/H]=0.32±0.11dex.利用星团中红团簇巨星作为理想"标准烛光",结合2MASS近红外点源测光数据计算了该星团的绝对距离模数为（m-M）0=13.02±0.08 mag或4.02±0.15 kpc.与其他研究者给出的结果进行了比较,金属丰度、视向速度及绝对距离模数都符合得比较好.主要结论有3点:（1）NGC 6791是个极度富金属的星团;（2）在SDSS的光谱分辨能力以内,分离出的87颗团星之间不存在明显的金属丰度差异;（3）得到的距离模数对年龄、金属丰度及尘埃消光不敏感,是一种可靠的间接测量. 相似文献
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The stellar spectroscopic data of SDSS-DR8 (The Eighth Data Release of Sloan Digital Sky Survey) and the near-infrared photometric data of 2MASS (Two Micron All Sky Survey) point sources are used to analyze the fundamental parameters of the open cluster NGC 6791. Using the radial velocities of 274 stars in the region of the cluster, we calculate the membership probability for each star with the maximum likelihood method. Based on the stars with high membership probabilities, we have derived the radial velocity and metal abundance of the cluster to be respectively Vr =−46.4±0.2 km·s−1 and [Fe/H]=0.32±0.11dex, in good agreement with the results obtained by other authors on the basis of high-resolution spectroscopy. Using red clump giants in the cluster as “standard candle”, we have derived the absolute distance modulus of the cluster to be (m − M)0 =13.02±0.08mag or 4.02±0.15 kpc in distance, consistent with the values obtained from main-sequence fittings by some authors. And our main conclusions are: (1) NGC 6791 is extremely metal-rich; (2) Within the spectral resolution of SDSS, the discriminated 87 cluster members have no evident difference in matallicity; (3) The obtained distance modulus is insensitive to the age, metallicity and dust distinction, so it is a kind of reliable indirect measurement. 相似文献
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