Global mass segregation in hydrodynamical simulations of star formation
Global mass segregation in hydrodynamical simulations of star formation
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恒星形成流体动力学模拟中的全局质量偏析
DOI：
10.1111/j.1365-2966.2011.19067.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
Ipag Grenoble
中科院分区：
文献类型：
--
作者：
T. Maschberger;C. J. C. IoA;Cambridge;A. Bonn;Ipag Grenoble
最近的分析质量分离诊断恒星形成的地区邀请比较流体动力学模拟的输出星星形成。在这项工作中，我们调查的状态质量分离的“明星”（即沉粒子在模拟）的情况下，流体动力学模拟忽略反馈。我们首先讨论的方法来量化质量分离的子结构区域，无论是基于最小生成树（艾利森的Λ），或通过分析恒星质量和本地恒星表面数密度之间的相关性。我们发现，即使存在一个“离群点”（即远离其他恒星的大质量物体），也会导致Allison Λ方法将系统描述为逆质量分离，即使在现实中最大质量的下沉粒子绝大多数位于子星系团的中心。我们证明，一个变种的Λ方法是不太容易受到这种趋势，但也主张在恒星质量与当地表面数密度的平面上的数据的另一种表示。
流体动力学模拟表明，全球质量隔离从很早的时候，继续在整个模拟，只有轻微的影响，在子集群合并。
我们发现，高达10.2%-3%的“大质量”下沉粒子（m > 2.5 M）是相对孤立的，因为它们已经在那里形成，尽管其他下沉粒子可以在它们附近形成。从子星系团中喷射出的大质量下沉粒子对孤立的大质量下沉粒子的数量没有贡献，因为计算中的引力软化抑制了这一过程。
Recent analyses of mass segregation diagnostics in star-forming regions invite a comparison with the output of hydrodynamic simulations of star formation. In this work we investigate the state of mass segregation of ‘stars’ (i.e. sink particles in the simulations) in the case of hydrodynamical simulations which omit feedback. We first discuss methods to quantify mass segregation in substructured regions, either based on the minimum spanning tree (Allison’s Λ), or through analysis of correlations between stellar mass and local stellar surface number densities. We find that the presence of even a single ‘outlier’ (i.e. a massive object far from other stars) can cause the Allison Λ method to describe the system as inversely mass segregated, even where in reality the most massive sink particles are overwhelmingly in the centres of the subclusters. We demonstrate that a variant of the Λ method is less susceptible to this tendency but also argue for an alternative representation of the data in the plane of stellar mass versus local surface number density.
The hydrodynamical simulations show global mass segregation from very early times which continues throughout the simulation, being only mildly influenced during subcluster merging.
We find that up to ≈2–3 per cent of the ‘massive’ sink particles (m > 2.5 M⊙) are in relative isolation because they have formed there, although other sink particles can form later in their vicinity. Ejections of massive sinks from subclusters do not contribute to the number of isolated massive sink particles, as the gravitational softening in the calculation suppresses this process.