天文学进展2017，Vol.35Issue(1)：107-118,12.DOI:10.3969/j.issn.1000-8349.2017.01.06
本星系群动力学质量之估测
Estimates of the Dynamical Mass of the Local Group of Galaxies
摘要
Abstract
The Milky Way (MW) is a member of a small group of galaxies called as the Local Group (LG).The LG is dominated by its two largest members,the MW and the Andromeda galaxy (M31).The other members can be separated into one of two categories:dwarf satellites accompanying the MW or M31,and the dozen or so independent galaxies sprinkled in space up to ～1.5 Mpc away.This group presents a unique example where sufficient data are available to derive its mass and dynamics,which has been the topic of many previous studies.Since 1959 the dynamical mass of the LG has been estimated in different ways,among which three independent methods have been most frequently used:the timing argument,the zero velocity surface and the virial theorem.The timing argument is to use the relative motion of MW and M31 to estimate the total mass of the LG.The methods of zero velocity surface and virial theorem use kinematic data of all satellite galaxies to estimate the LG mass.Furthermore,in the zero velocity surface method the mass of the LG is determined from the external Hubble velocity field surrounding the group,and the virial mass is derived from the internal motions of member galaxies of the LG.In order to estimate the dynamical mass of the LG by using the timing argument,one must know the three dimensional kinematical data of M31 with respect to the MW.While the light-of-sight velocity of M31 is well known from Doppler measurements,determining its proper motions has been elusive for some half century or longer,because M31 is very far away from us.Recently,the first proper motion measurements were obtained with the HST equipments and have been used to derive the mass of the LG.The major results for the mass of the LG,MLG,obtained from different approaches since 1959,are collected in Table 1 and briefly discussed.It can be seen from the table that the range of MLG is 1.2 ＜ MLG ＜ 5.6,discrepancies being quite big.However,the range of MLG published in the recent years (2009 2014) has been obviously narrowed to 1.88 ＜ MLG ＜ 4.27,from which an optimum estimator MLG =(2.73 ± 0.44) × 1012M☉ can be found.关键词
本星系群/银河系/仙女星系/径向速度/横向速度/动力学质量Key words
Local Group/Milky Way Galaxy/Andromeda galaxy (M31)/radial velocity/transverse velocity/dynamical mass分类
天文与地球科学引用本文复制引用
赵君亮..本星系群动力学质量之估测[J].天文学进展,2017,35(1):107-118,12.基金项目
国家自然科学基金(11373054) （11373054）
中国科学院战略性先导专项B类(XDB09010100) （XDB09010100）
