摘要
本文利用Virgo星系团天区572个星系的视向速度观测资料,按最大似然原理确定了434个成员星系。平均日心速度1247±37公里每秒,视向速度弥散度752±27公里·每秒。分析表明,尽管室女团是一个有次团结构的近距星系团,仍然可以合理地用正态分布来作为成员星系观测视向速度分布的一级近似。另外,团内不同类型的星系看来有着不同的分布,而晚型星系可能仍然处于内落阶段。
Using the radial velocity data of 572 galaxies in the Virgo Cluster area taken from the catalogue compiled by Binggeli, Sandage and Tammann, a successful membership study for the cluster has been made based upon the method developed by us according to the maximum likelihood principle. 434 member galaxies with membership probabilities. greater than 0.9 are found. An average heliocentric velocity of 1247±37kms-1 and a radial velocity dispersion of 752 ±27 kms-1 are determined. It is concluded from a detailed discussion that normal distribution can be reasonably used as a first order approximation to the observed radial velocities of the Cluster members, although it is a nearby cluster with significant substructure.On the other hand, no matter the radial velocities of field galaxies are considered to follow one or two one-dimensional normal distributions, determinations of distribution parameters and membership probabilities and the discrimination between cluster members and field galaxies are very satisfactory, with two obvious peaks at pc=0 and 1 in the frequency distribution of membership probabilities. In addition, member galaxies with different Hubble types in the Virgo Cluster have different surface distributions, and the late type galaxies in the cluster seem to be still in a stage of infall or to have fallen into th cluster only recently.
