河外星系动力学质量的多途径测定

摘要

利用伴天体(含伴星系、球状星团、晕族天体等)的运动学观测资料,可通过多种方法估测主星系的质量(动力学质量),如自转质量、位力质量、轨道质量、投影质量、示踪质量以及星流法质量等.在诸多已测得动力学质量的河外星系中,以仙女星系(M31)的相关工作为最多,对此做了简要的介绍和讨论.%Kinametic data of satellite ob jects of external galaxies, such as dwarf galaxies, globular clusters and other halo population objects, have been used to estimate the dynamic masses of the galaxies in different approaches, including rotation mass, virial mass, pro jected mass and TME mass (Tracer Mass Estimator), orbital mass, timing mass, stellar stream method etc. During the 20th century, the main methods for mass estimates of galaxies are rotation mass, pro jected mass and orbital mass. In the 21st century, the current approaches turn to TME mass and stellar stream method, while virial mass and timing mass are also used. Among the external galaxies for which the dynamical masses have been estimated, the most numerous work of mass determination is on Andromeda, M31, and the concerned results are listed in Table 1 of this paper. It can be seen from these results that the uncertainties of M31's mass estimators, MA, are usually quite big, and even bigger than MA itself in a few cases. Because of such big uncertainties of mass estimators, up to now there has not been the final conclusion for the most massive member galaxy in the Local Group, Andromeda or Milky Way Galaxy? So far as Andromeda is concerned, it can be found from the table that the reasonable estimate of its mass, MA, is likely to be MA=(11～15) × 1011 M⊙ based on the results obtained during the recent 5～10 years. The dynamic masses of some other external galaxies with different types are briefly introduced, including the cD galaxy M87, the lenticular galaxy NGC5084, the special galaxy NGC1961, the barred spiral galaxy NGC3992, and the quasar 3C273. The GAIA satellite was successfully launched in December 2013. It will allow the determination of the proper motions of some 100 globular clusters with 20 < R < 50 kpc within the following years. It can be expected that then the relative uncertainty of the mass MA will be reduced to some 20%.