论文标题

在使用混合MHD和直接N体方法的恒星簇形成模拟中实现原始二进制

Implementing Primordial Binaries in Simulations of Star Cluster Formation with a Hybrid MHD and Direct N-Body Method

论文作者

Cournoyer-Cloutier, Claude, Tran, Aaron, Lewis, Sean, Wall, Joshua E., Harris, William E., Mac Low, Mordecai-Mark, McMillan, Stephen L. W., Zwart, Simon Portegies, Sills, Alison

论文摘要

恒星簇中二进制系统中恒星的比例对于它们的进化很重要,但是在初始恒星积聚后,通过动力学过程形成二进制的比例仍然未知。在先前的工作中,我们表明,与观测相比,单独的动态相互作用产生的低质量二进制文件太少。因此,我们在耦合的MHD和直接N-Body Star群集形成码火炬中实施初始二进制群。我们将模拟与初始二元种群进行了比较,并遵循两组仿真中二元种群的动态演变,发现发生了动态形成和二进制的破坏。即使在恒星形成的前几百万年中,我们也发现,在所有群众中都需要初始二进制群来繁殖观察到的二元分数,该二进制要素的质量比高于$ q \ geq 0.1 0.1 $检测限。我们的模拟还表明,在簇形成过程中存在气体的动态相互作用会改变针对较小的原始质量,较大的质量比,较小的半高轴和较大偏心率的初始分布。动态形成的系统与初始系统没有相同的属性,并且在存在初始二进制组的情况下,动态形成的系统与仅在单颗恒星的模拟中形成的系统不同。在星团形成的最早阶段,动态相互作用对于确定二进制恒星系统的性质很重要。

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 MHD and direct N-body star cluster formation code Torch. 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 the $q \geq 0.1$ 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 semi-major 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.

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