Implementing primordial binaries in simulations of star cluster formation with a hybrid MHD and direct N -body method
Implementing primordial binaries in simulations of star cluster formation with a hybrid MHD and direct N -body method
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使用混合 MHD 和直接 N 体方法在星团形成模拟中实现原始双星
DOI：
10.1093/mnras/staa3902
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发表时间：
2021
影响因子：
4.8
通讯作者：
Sills, Alison
中科院分区：
文献类型：
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作者：
Cournoyer-Cloutier, Claude;Tran, Aaron;Lewis, Sean;Wall, Joshua E;Harris, William E;Mac Low, Mordecai-Mark;McMillan, Stephen L;Portegies Zwart, Simon;Sills, Alison
星团内双星系统中恒星的比例对它们的演化很重要，但在初始恒星吸积后，有多大比例的双星是由动力学过程形成的，目前尚不清楚。在之前的工作中，我们表明，与观测相比，单靠动力相互作用产生的小质量双星太少了。因此，我们在耦合磁流体力学和直接N体星团形成代码炬中实现了双星群的初始群。我们比较了有和没有初始双星种群的模拟，并在两组模拟中跟踪了双星种群的动态演化，发现双星的动态形成和破坏都发生了。即使在恒星形成的最初几百万年里，我们也发现在所有质量上都需要一个初始的双星群来重现观测到的质量比超过q≥0.1.1探测极限的双星的双星分数。我们的模拟还表明，在星团形成过程中，气体存在的动力学相互作用改变了双星的初始分布，这些双星具有较小的初级质量、较大的质量比、较小的半长轴和较大的偏心率。动态形成的系统不具有与初始系统相同的性质，并且在存在初始双星群的情况下动态形成的系统与仅用单星模拟形成的系统不同。星团形成初期的动力学相互作用对于确定双星系统的性质是很重要的。
The fraction of stars in binary systems within star clusters is important for their evolution, but what proportion of binaries form by dynamical processes after initial stellar accretion remains unknown. In previous work, we showed that dynamical interactions alone produced too few low-mass binaries compared to observations. We therefore implement an initial population of binaries in the coupled magnetohydrodynamics and directN-body star cluster formation codetorch. We compare simulations with, and without, initial binary populations and follow the dynamical evolution of the binary population in both sets of simulations, finding that both dynamical formation and destruction of binaries take place. Even in the first few million years of star formation, we find that an initial population of binaries is needed at all masses to reproduce observed binary fractions for binaries with mass ratios above theq≥ 0.1 detection limit. Our simulations also indicate that dynamical interactions in the presence of gas during cluster formation modify the initial distributions towards binaries with smaller primary masses, larger mass ratios, smaller semimajor axes and larger eccentricities. Systems formed dynamically do not have the same properties as the initial systems, and systems formed dynamically in the presence of an initial population of binaries differ from those formed in simulations with single stars only. Dynamical interactions during the earliest stages of star cluster formation are important for determining the properties of binary star systems.