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arXiv 2302.08536astro-ph.GA
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内嵌星团的早期演化与三维结构

Early Evolution and 3D Structure of Embedded Star Clusters

Claude Cournoyer-Cloutier, Alison Sills, William E. Harris, Sabrina M. Appel, Sean C. Lewis, Brooke Polak, Aaron Tran, Maite J. C. Wilhelm, Mordecai-Mark Mac Lo… 展开作者

Claude Cournoyer-Cloutier, Alison Sills, William E. Harris, Sabrina M. Appel, Sean C. Lewis, Brooke Polak, Aaron Tran, Maite J. C. Wilhelm, Mordecai-Mark Mac Low, Stephen L. W. McMillan, Simon Portegies Zwart

AI总结:

本研究通过Torch模拟工具开展星团形成模拟,探究内嵌星团早期演化与三维结构,揭示了其质量变化、形态演化规律及极年轻星团动力学演化的主导因素。

摘要:

我们开展星团形成模拟,以探究内嵌星团在演化最早期阶段的形态演化过程。我们使用Torch(一种星团形成模拟工具)开展模拟,该工具借助AMUSE(天体物理多用途软件环境)框架,将最先进的恒星动力学与FLASH中的恒星形成、辐射、恒星风及流体动力学相耦合。我们对一系列质量为10⁴倍太阳质量(M☉)的分子云进行模拟,空间分辨率为0.0683秒差距(pc),模拟时长为恒星形成开始后约2百万年(Myr),设置的位力参数α分别为0.8、2.0、4.0,同时采用恒星初始质量函数的不同随机采样方案以及原初双星的不同预设规则。我们的模拟得到了一族具有真实形态(尺寸、密度和椭率)的内嵌星团,重现了已知的趋势:初始α值更高的分子云具有更低的恒星形成效率。我们的核心结果如下:(1)星团的质量增长并非单调过程,在内嵌阶段星团最多可能损失一半的质量。(2)星团形态与星团质量无相关性,且会在约0.01百万年的时间尺度上发生变化。(3)内嵌星团的形态无法指示其长期演化,仅能反映其近期历史:当星团吸积恒星时,半径和椭率会急剧增大。(4)质量≲1000倍太阳质量的极年轻内嵌星团,其动力学演化由恒星形成区的整体引力势主导,而非由两体或多体弛豫这类内部动力学过程主导。

英文摘要:

We perform simulations of star cluster formation to investigate the morphological evolution of embedded star clusters in the earliest stages of their evolution. We conduct our simulations with Torch, which uses the AMUSE framework to couple state-of-the-art stellar dynamics to star formation, radiation, stellar winds, and hydrodynamics in FLASH. We simulate a suite of $10^4$ M$_{\odot}$ clouds at 0.0683 pc resolution for $\sim$ 2 Myr after the onset of star formation, with virial parameters $α$ = 0.8, 2.0, 4.0 and different random samplings of the stellar initial mass function and prescriptions for primordial binaries. Our simulations result in a population of embedded clusters with realistic morphologies (sizes, densities, and ellipticities) that reproduce the known trend of clouds with higher initial $α$ having lower star formation efficiencies. Our key results are as follows: (1) Cluster mass growth is not monotonic, and clusters can lose up to half of their mass while they are embedded. (2) Cluster morphology is not correlated with cluster mass and changes over $\sim$ 0.01 Myr timescales. (3) The morphology of an embedded cluster is not indicative of its long-term evolution but only of its recent history: radius and ellipticity increase sharply when a cluster accretes stars. (4) The dynamical evolution of very young embedded clusters with masses $\lesssim$ 1000 M$_{\odot}$ is dominated by the overall gravitational potential of the star-forming region rather than by internal dynamical processes such as two- or few-body relaxation.

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