标题： 星团的银河系轨道运动：静态与半宇宙学时间相关的银河系势能 显示英文标题

标题： Galactic orbital motions of star clusters: static versus semicosmological time-dependent Galactic potentials

摘要： 为了理解银河系晕星团等星团的轨道历史，作者通常假设银河系具有静态引力势，并采用当前时刻观测到的参数。根据星系形成的经典模型，星系通过从高红移至现今持续吸积新鲜气体以及与较小星系的层级合并而增长。这意味着盘、核球和晕的质量和大小随时间变化。我们研究了假设动态银河系引力势对晕星团轨道历史及其内部演化的影响。为了判断是否可以区分静态和动态引力势下不同位置的星团的轨道历史，我们数值反向积分了位于不同银心距处的测试天体的动力学方程，在静态和动态引力势中分别计算。我们表明，在动态引力势中，这些天体在13 Gyr前的诞生位置比在静态引力势中的轨道位置要远得多。基于用NBODY6碰撞N体代码直接进行的星团N体计算，我们还通过比较分别代表当前和12 Gyr前银河系的两个嵌入式星团的演化，以简单的方式讨论了银河系引力势的时间依赖性对星团早期和长期演化的后果。我们表明，像经常所做的那样假设银河系在整个哈勃时间内的静态引力势会导致质量损失增加、球状星团瓦解率高估、星团最终尺寸低估以及恒星质量函数变浅。 显示英文摘要

摘要： In order to understand the orbital history of Galactic halo objects, such as globular clusters, authors usually assume a static potential for our Galaxy with parameters that appear at the present-day. According to the standard paradigm of galaxy formation, galaxies grow through a continuous accretion of fresh gas and a hierarchical merging with smaller galaxies from high redshift to the present day. This implies that the mass and size of disc, bulge, and halo change with time. We investigate the effect of assuming a live Galactic potential on the orbital history of halo objects and its consequences on their internal evolution. We numerically integrate backwards the equations of motion of different test objects located in different Galactocentric distances in both static and time-dependent Galactic potentials in order to see if it is possible to discriminate between them. We show that in a live potential, the birth of the objects, 13 Gyr ago, would have occurred at significantly larger Galactocentric distances, compared to the objects orbiting in a static potential. Based on the direct N-body calculations of star clusters carried out with collisional N-body code, NBODY6, we also discuss the consequences of the time-dependence of a Galactic potential on the early- and long-term evolution of star clusters in a simple way, by comparing the evolution of two star clusters embedded in galactic models, which represent the galaxy at present and 12 Gyr ago, respectively. We show that assuming a static potential over a Hubble time for our Galaxy as it is often done, leads to an enhancement of mass-loss, an overestimation of the dissolution rates of globular clusters, an underestimation of the final size of star clusters, and a shallower stellar mass function.