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arXiv 2006.01960astro-ph.GA
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潮汐场中大质量球状星团的质量损失

Mass loss from massive globular clusters in tidal fields

Yohai Meiron, Jeremy J. Webb, Jongsuk Hong, Peter Berczik, Rainer Spurzem, Raymond G. Carlberg

摘要:

大质量球状星团通过内部和外部过程失去恒星。内部过程主要包括两体弛豫,而外部过程包括与银河潮汐场的相互作用。我们使用三种不同的直接求和N-体代码,探索不同的银河系轨道和粒子数的N-体模拟这样的大规模集群。通过检查恒星能量变化的速率,当它从星系团中脱离出来时,我们可以清楚地识别出两种我们称之为踢和扫的种群,它们分别通过星系团内部和外部潮汐场的两体相遇逃逸。我们发现,对于一个典型的晕球状星团在一个中等偏心的轨道上,扫比踢更常见,但总的质量损失率是如此之低,这些集群可以生存几十哈勃倍。不同的N-体代码给出了大致一致的结果,但我们发现,数值文物可能会出现有关的时间步长参数的Hermite积分方案,即收敛结果所需的值是敏感的粒子数。

英文摘要:

Massive globular clusters lose stars via internal and external processes. Internal processes include mainly two-body relaxation, while external processes include interactions with the Galactic tidal field. We perform a suite of N-body simulations of such massive clusters using three different direct-summation N-body codes, exploring different Galactic orbits and particle numbers. By inspecting the rate at which a star's energy changes as it becomes energetically unbound from the cluster, we can neatly identify two populations we call kicks and sweeps, that escape through two-body encounters internal to the cluster and the external tidal field, respectively. We find that for a typical halo globular cluster on a moderately eccentric orbit, sweeps are far more common than kicks but the total mass loss rate is so low that these clusters can survive for tens of Hubble times. The different N-body codes give largely consistent results, but we find that numerical artifacts may arise in relation to the time step parameter of the Hermite integration scheme, namely that the value required for convergent results is sensitive to the number of particles.

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