Formation of Globular Clusters in Galaxies

我们建立了大麦哲伦云和小麦哲伦云（LMC和SMC）的轨道模型，以重现麦哲伦流中氢气的密度和速度分布。在成功的模型中，LMC和SMC来自引力束缚对，它们在过去- 10^<10 b> y的时间里围绕银河系旋转。它们每- 10^9 y经历一次近距离接触，并被潮汐力反复搅动，使星际气体保持湍流，湍流速度高于(]SY.gtoreq。[] 50 km s^<-1>。湍流涡旋（气体云）经常相互碰撞，在界面处形成压缩气体层。由于碰撞通常是偏离中心的，而且很少是正面的，因此压缩气体层会旋转并产生内部速度剪切。我们的线性稳定性分析表明，压缩气体层在引力作用下分裂成质量为10^4 - 10^6 M_<(] SY.sun)的团块。[)>，当它的质量增长，它的自我引力变得可观。气态团块由于其高密度而迅速冷却，并级联成更小的碎片，最终形成引力束缚的恒星系统或球状星团。因此我们得出结论，球状星团不是只在早期宇宙中形成的宇宙物体，而是在星系中任何时代形成的普通天体，其中大量星际气体以高于50 km s^<-1>的速度进行无组织运动。球状星团的颜色、年龄和质量分布表明了宿主星系所经历的动态事件的历史。

We made a model for the orbits of the Large and Small Magellanic Clouds (LMC and SMC) to reproduce the density and velocity destribution of hydrogen gas in the Magellanic stream. In the successful model LMC and SMC from a gravitationally bound pair and have revolved around the Galaxy over the past - 10^<10> y. They exprienced a close encounter every - 10^9 y and have been agitated by tidal force repeatedly to keep the interstellar gas turbulent with the turbulent velocity higher than (〕SY.gtoreq.〔) 50 km s^<-1>.Turbulent eddies (gas clouds) collide with each other frequently and form compressed gas layers at the interfaces. The compressed gas layrs rotate and have internal velocity shear because the collisions are usually off-center and rarely head-on. Our linear stability analysis showed that the compressed gas layrs fragment into gravitationally bound clumps with the mass of 10^4 - 10^6 M_<(〕SY.sun.〔)> after it grows in mass and its self-gravity becomes appreciable. The gaseous clumps cool rapidly due to their high density and cascade into much smaller fragments, finally froming gravitationally-bound stellar systems or globular clusters.We thus conclude that globular clusters are not cosmological objects formed only in the early universe but ordinary ones formed at any epoch in the galaxies in which a large amount of interstellar gas has an unorganized motion with the velocity higher than 50 km s^<-1>. The color, age, and mass distributions of globular clusters manifest the history of the dynamical events experienced by the host galaxy.