Time Scales and Tidal Effects in Minor Mergers
We use controlled N-body simulation to investigate the dynamical processes (dynamical friction, tidal truncation, etc.) involved in the merging of small satellites into bigger halos. We confirm the validity of some analytic formulae proposed earlier based on simple arguments. For rigid satellites represented by softened point masses, the merging time scale depends on both the orbital shape and concentration of the satellite. The dependence on orbital ellipticity is roughly a power law, as suggested by Lacey & Cole, and the dependence on satellite concentration is similar to that proposed by White. When merging satellites are represented by non-rigid objects, Tidal effects must be considered. We found that material beyond the tidal radius are stripped off. The decrease in the satellite mass might mean an increase in the merging time scale, but in fact, the merging time is decreased,because the stripped-off material carries away a proportionately larger amount of of orbital energy and angular momentum.
作 者： Yu Lu Jian-Yan Wei 作者单位： National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 刊 名： 天体物理学报(英文版) ISTIC SCI 英文刊名： CHINESE JOURNAL OF ASTRONOMY AND ASTROPHYSICS 年，卷(期)： 2003 3(5) 分类号： P14 关键词： cosmology: dark matter - galaxies: kinematics and dynamicsgalaxies: structure - galaxies: interactions - numerical methods