Formation of Globular Clusters in Galaxies

我们建立了大小麦哲伦云(LMC和SMC)的轨道模型，再现了氢气在麦哲伦流中的密度和速度分布。在成功的模型中，LMC和SMC来自引力束缚对，在过去的-10^&10&gt；y围绕银河系旋转。它们每-10^9年经历一次近距离相遇，并反复受到潮汐作用力的搅动，以保持星际气体湍流的湍流速度高于50公里S。湍涡(气云)频繁地相互碰撞，并在界面形成压缩气体层。压缩气层旋转并有内部速度剪切，因为碰撞通常是偏心的，很少是迎头碰撞。我们的线性稳定性分析表明，压缩气层在质量增长和自重变得明显后，碎裂成质量为10^4-10^6 M_&lt；()&gt；的重力束缚团块。气团由于密度高而迅速冷却，并级联成更小的碎片，最终形成引力束缚的星系团或球状星团。因此，球状星团不是只在早期宇宙中形成的宇宙学物体，而是在星系中任何时期形成的普通物体，在星系中，大量星际气体以高于50公里的速度无组织地运动。球状星团的颜色、年龄和质量分布显示了宿主星系经历的动力学事件的历史。

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.