致密星团的分层效应及其形成机制  

Mass Segregation of Compact Star Clusters and its Origins

作　　者：赵君亮[1] 

机构地区：[1]中国科学院上海天文台,上海200030

出　　处：《天文学进展》2008年第3期257-265,共9页Progress In Astronomy

基　　金：国家自然科学基金面上(10773020)

摘　　要：老年球状星团和年轻的超星团是两类不同性质的致密星团,观测表明它们都表现出某种程度的质量分层效应。该文在介绍这两类星团质量分层的探测途径和观测表象的基础上,对形成这种分层效应的两种可能的机制——动力学分层和原初分层做了简要的讨论和评述.The phenomenon of mass segregation of a star cluster means a preferential concentration of high mass stars towards the cluster center and a preferential allocation of lower mass stars towards the periphery of the cluster,which seems to occur in star systems with widely distinct physical properties.As a kind of compact star systems,globular clusters are very old ones with ages of older than 10^10years,which are different from another kind of young compact clusters, super star clusters（SSC）or massive young clusters（MYC）,with ages ranging from a few 10^6 to 10^8 years.It is interesting that mass segregation of member stars has been observed for these two kinds of compact clusters. An important observational effect of mass segregation of a star cluster is expected that the slopeαof the PDMF（present day mass function）of the cluster is dependent on radial distance r from the cluster center,in the senseαbecoming steeper with r increasing.This radial variation of the mass function reveals mass segregation for both old globular clusters and young SSC or MYC.On the other hand,it is found that stars of different masses in a cluster show the pronounced,systematic variations of the core radius,which is another observational effect of mass segregation.Mass segregation mainly affects the innermost region of clusters,while dynamical interaction with the Galaxy acts predominantly their outermost regions inducing stellar evaporation and stripping. Further evidence of mass segregation in a globular cluster comes from the detection of color gradients whereby the color indices such as（U-B）or（B-V）get bluer towards the cluster center.A possible explanation for such color gradients is mass segregation of main sequence （MS）stars,since stars near the MS turnoff,with higher and bluer color,are expected to be more centrally concentrated than the fainter,redder,and lower mass stars.A core concentration of blue stars is likely due to binary-single star interaction or the central lack of low mass MS stars. Mass segreg

关 键 词：天体物理学 星团 球状星团 超星团 质量分层 形成机制 

分 类 号：P154.1[天文地球—天文学]