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恒星蛇起源的数值模拟研究

Numerical Simulation Study on the Origin of Stellar Snakes

  • 摘要: 得益于近几年观测技术的进步, 对疏散星团的搜寻有了很大的发展. 这其中双疏散星团由于其特殊的性质及复杂的相互作用成为星团研究的重点. 疏散星团NGC 2232与Tian 2彼此距离极近, 被认为是双星团系统. 观测表明, 这两个星团都具有非常年轻且相似的年龄(约30\sim40 Myr), 在双星团附近存在一条长度超过200 pc且由恒星形成的结构, 该结构被称为“恒星蛇”. 通过一系列高精度N体动力学数值模拟对恒星蛇的形成进行了动力学建模(N为研究对象的数量). 结果显示, 目前两个星团处于非动力学束缚状态, 且无法确定其形成时刻是否为引力束缚状态. 在初始非束缚模型中, 星团的质量损失过程没有明显高于银河系中的单星团潮汐剥离速率. 而在初始束缚模型中, 双星团在系统内相互绕转所产生的潮汐作用显著加速了疏散星团的质量损失, 使得被剥离的恒星形成了更大的潮汐结构, 但仍然未能有效形成类似恒星蛇这样超过200 pc的潮汐流. 同时考虑观测到的恒星蛇为单侧结构, 不符合潮汐作用产生的导臂和曳臂对称结构. 因此, 恒星蛇结构并非由潮汐作用引起的动力学效应所产生, 而更可能因原始气体沿纤维结构坍缩形成.

     

    Abstract: Thanks to recent advancements in observational technology, significant progress has been made in the search for open clusters. Among these, binary open clusters have become a key focus of cluster studies due to their unique properties and complex interactions. The open clusters NGC 2232 and Tian 2, which are located at a very close distance from each other, are considered a binary cluster system. Observations show that these two clusters have very young and similar ages (approximately 30\sim40 Myr). There is a structure formed by stars with a length exceeding 200 pc near the binary star cluster, which is called the “Stellar Snake". Through a series of high-precision N-body dynamical simulations (N: the number of bodies), the formation of the stellar snake has been dynamically modeled. The simulation results indicate that the two clusters are currently in a non-dynamically bound state, and it remains uncertain whether they were bound at the time of their formation. If the system is initially considered unbound, the two clusters show no significant mass loss after independently evolving for 100 Myr, and their mass loss rate is not significantly higher than that of a single open cluster in the Milky Way under tidal stripping. In contrast, if the two clusters were initially bound at birth and evolved together for 100 Myr, the tidal effects from mutual orbital motion within this bound system significantly accelerated the mass loss of the clusters. As a result, the stripped stars formed a larger tidal structure, but the tidal stream did not effectively form a structure resembling the stellar snake with a span over 200 pc. Additionally, considering the observed stellar snake as a one-sided structure, it does not match the symmetric tidal arms and tails that would be expected from tidal interactions. Therefore, the stellar snake is not likely to be a product of tidal effects, but rather a formation mechanism more consistent with the collapse of primordial gas along a filamentary structure.

     

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