疏散星团NGC 6530的光度函数和分层效应

LUMINOSITY FUNCTION AND SEGREGATION EFFECT OF THE OPEN CLUSTER NGC 6530

该文利用疏散星团NGC 6530的自行观测数据和成员判别结果,给出了星团的光度函数,并详细讨论了星团的质量分层效应。分析表明,NGC 6530存在空间质量分层效应,但并不存在速度质量分层,因此星团的表观空间质量分层可能起因于星团形成时的初始条件,而不是动力学弛豫的结果。

Using the observational data of the open cluster NGC 6530 of Shanghai Astronomical Observatory and the proper motion membership determined on the basis of the data, the luminosity function of the cluster is given and its mass segregation effect is discussed in some details. From analyses on the luminosity functions of members in different areas of the cluster, the radial number density profiles of members with different masses and the half-mass or half-light radii of various mass or magnitude groups of members, it is shown that there exists the spatial mass segregation for the cluster, but there are no definitive evidences to demonstrate the velocity-mass dependence or the velocity mass segregation of cluster members, from which it may be concluded that the apparent spatial mass segregation of the cluster is very likely mainly due to the initial conditions when the cluster formed instead of the two-body relaxation process afterwards.