球状动力学系统的基本面--从椭圆星系到球状星团

The Tilt of Fundamental Plane:from Elliptical Galaxies to Globular Clusters

基本面是球状动力学系统的有效半径、中心速度弥散度和平均面亮度三者之间的相关关系。椭圆星系和球状星团的基本面都与位力面发生偏离。评述了两者基本面的研究进展,并对基本面偏离位力面的原因进行探讨。球状系统偏离位力面的原因,通常可以归结为系统结构的非均一性和非常数的质光比。对于这两个不同尺度的动力学系统,其非常数的质光比的起因是不同的:对于椭圆星系,质光比的变化主要是由暗物质含量或是初始质量函数的变化导致的;对于球状星团,二体弛豫时标短,动力学演化是导致其质光比改变的主要原因。

The fundamental plane(FP)is a scaling relation among effective radius,central velocity dispersion and average surface brightness of spherical dynamical systems,which is expected to be originated from the virial equilibrium of their members.However,observations show that the FPs of elliptical galaxies,as well as globular clusters are both tilted from virial plane.This paper gives an overview on the FP studies of elliptical galaxies and globular clusters and makes comparisons.The non-homologous structure and non-constant mass-tolight ratio are the main reasons of the FP tilt.For elliptical galaxies,the variation of massto-light ratio is originated from the change of dark matter fraction and possible variation of the stellar initial mass function in different mass systems.For globular clusters,the two-body relaxation timescale of stars is much shorter,where the dynamical evolution makes the main contribution to their non-constant mass-to-light ratios.