Mass segregation in very young open clusters: A case study of NGC 2244 and NGC 6530

被引:74
作者
Chen, L.
De Grijs, R.
Zhao, J. L.
机构
[1] Chinese Acad Sci, Shanghai Astron Observ, Shanghai 200030, Peoples R China
[2] Univ Sheffield, Dept Phys & Astron, Sheffield S3 7RH, S Yorkshire, England
[3] Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
关键词
astrometry; open clusters and associations : general; open clusters and associations : individual ( NGC 2244; NGC; 6530); stellar dynamics;
D O I
10.1086/521022
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We derive the proper motions, membership probabilities, and velocity dispersions of stars in the regions of the young (similar to 2 - 4 Myr old) open clusters NGC 2244 ( the central cluster in the Monoceros R2 association) and NGC 6530 ( the dominant cluster in the Sgr OB1 association) from photographic plate material obtained at Shanghai Astronomical Observatory, with time baselines of 34 and 87 yr, respectively. Both clusters show clear evidence of mass segregation, but they do not exhibit any significant velocity- mass ( or, equivalently, velocity- luminosity) dependence. This provides strong support for the suggestion that the observed mass segregation is at least partially due to the way in which star formation has proceeded in these complex star- forming regions ("primordial'' mass segregation). Based on arguments related to the clusters' published initial mass functions, in conjunction with our new measurements of their internal velocity dispersions (similar to 35 and 8 km s(-1) for NGC 2244 and NGC 6530, respectively), we provide strong arguments in favor of the dissolution of NGC 2244 on very short timescales, while we speculate that NGC 6530 may be more stable against the effects of internal two- body relaxation. However, this latter object may well be destroyed by the strong tidal field prevalent at its location in the Galactic plane in the direction of the Galactic center.
引用
收藏
页码:1368 / 1379
页数:12
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