基于混合模型的疏散星团视向速度和金属丰度研究  

Radial Velocities and Metallicities of Open Clusters Based on Mixture Model

作　　者：张书会 刘蓉蓉 李璐 胡国真 邵正义[1,3] ZHANG Shu-hui;LIU Rong-rong;LI Lu;HU Guo-zhen;SHAO Zheng-yi(Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China;U-niversity of Chinese Academy of Sciences,Beijing 100049,China;Shanghai Key Lab for Astrophysics,Shanghai Normal University,Shanghai 200234,China)

机构地区：[1]中国科学院上海天文台,上海200030 [2]中国科学院大学,北京100049 [3]上海师范大学上海市星系与宇宙学半解析研究重点实验室,上海200234

出　　处：《天文学进展》2023年第3期388-400,共13页Progress In Astronomy

基　　金：国家自然科学基金(U2031139,12273091);国家重点研发项目(2019YFA0405501);中国载人航天工程科研基金(CMS-CSST-2021-A08)。

摘　　要：疏散星团是研究星族和银河系形成与演化的理想示踪体。基于LAMOST DR7低分辨率光谱,在视向速度和金属丰度两维空间上,构建包含团星和场星的混合模型:以二维正高斯模型来描述团星的分布,以星团天区周围的恒星来构建场星的分布模型。同时,在模型中考虑了观测误差的影响。对3个具有丰富光谱数据的典型疏散星团进行了拟合。年轻星团Melotte 22和中年星团NGC 2281可以较好地约束其视向速度的内禀弥散,分别为:1:47_(−1:18)^(+0:95)km·s^(−1)和2:05_(−1:88)^(+1:39)km·s^(−1),而年老星团NGC 2682只能给出速度弥散的上限约为0:96 km·s^(−1)。Melotte 22、NGC 2281和NGC 2682的金属丰度内禀弥散分别为:0:170_(−0:009) ^(+0:012)dex,(0:1080:012)dex和(0:0500:005)dex,都明显大于金属丰度的观测误差(约0:028 dex)。这说明疏散星团的成员星存在一定的化学丰度内禀弥散,这对于进一步讨论星团恒星的形成过程极为重要。Open clusters are excellent tracers to study the stellar population and the formation and evolution of the Galactic Disk.Based on the LAMOST DR7 low-resolution spectra,a mixture model including cluster and field stars is constructed in two dimensions of radial velocity and metallicity:a two-dimensional positive Gaussian model is used to describe the distribution of cluster stars whereas the distribution of field stars is modeled by the stars around the cluster sky region.At the same time,the effect of observational errors is considered in the model.Three typical open clusters with rich spectroscopic data are fitted.The young cluster Melotte 22 and the intermediate-age cluster NGC 2281 can better constrain intrinsic dispersion of radial velocity with 1:47_(−1:18)^(+0:95)km·s^(−1)and 2:05_(−1:88)^(+1:39)km·s^(−1),respectively,while the old cluster NGC 2682 only give an upper limit of intrinsic dispersion of radial velocity about 0.96 km·s^(−1).The intrinsic dispersion of the metallicity of Melotte 22,NGC 2281 and NGC 2682 are 0:170_(−0:009) ^(+0:012)dex,(0.1080.012)dex and(0.0500.005)dex,all significantly larger than the observed error of metallicity(0.028 dex).This suggests that there is a certain dispersion of metallicity in the member stars of open clusters,which is extremely important for further discussion of the cluster star formation process.

关 键 词：疏散星团 混合模型 LAMOST 视向速度 金属丰度 

分 类 号：P154.11[天文地球—天文学]