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arXiv 1802.01600astro-ph.GA
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麦哲伦流中潮汐诱导气丝的模型

Models of Tidally Induced Gas Filaments in the Magellanic Stream

Stephen A. Pardy, Elena D'Onghia, Andrew J. Fox

摘要:

从大麦哲伦云和小麦哲伦云(LMC和SMC)延伸到南半球天空200度以上的麦哲伦流和HI的主导臂被认为是由LMC和SMC之间的多次相遇形成的。在这种情况下,流和引导臂中的大部分气体都是从SMC中剥离出来的,但最近的观测显示,尾臂的分叉揭示了一些气体的LMC起源。在流中的吸收测量也揭示了一个数量级以上的气体比目前的潮汐模型。我们提出的流体动力学模拟LMC和SMC之间的多次相遇,在他们的第一次通过银河系周围,假设云是更广泛的和丰富的气体在过去。我们的模型在尾流中从LMC和SMC中创建了气体的非线性结构。虽然SMC尾丝与观测到的流位置相匹配,但LMC丝偏移。此外,在这些模型中的总观测质量的流被低估的四个因素时,电离的成分占。我们的研究结果表明,也应该有气体剥离的LMC和SMC在领导臂,反映在尾流的分叉。这一预测与最近对主导臂化学丰度空间变化的测量结果一致,这表明存在来自多个来源的气体,尽管性质仍然不确定。

英文摘要:

The Magellanic Stream and Leading Arm of HI that stretches from the Large and Small Magellanic Clouds (LMC and SMC) and over 200 degrees of the Southern sky is thought to be formed from multiple encounters between the LMC and SMC. In this scenario, most of the gas in the Stream and Leading Arm is stripped from the SMC, yet recent observations have shown a bifurcation of the Trailing Arm that reveals LMC origins for some of the gas. Absorption measurements in the Stream also reveal an order of magnitude more gas than in current tidal models. We present hydrodynamical simulations of the multiple encounters between the LMC and SMC at their first pass around the Milky Way, assuming that the Clouds were more extended and gas rich in the past. Our models create filamentary structures of gas in the Trailing Stream from both the LMC and SMC. While the SMC trailing filament matches the observed Stream location, the LMC filament is offset. In addition, the total observed mass of the Stream in these models is underestimated of a factor of four when the ionized component is accounted for. Our results suggest that there should also be gas stripped from both the LMC and SMC in the Leading Arm, mirroring the bifurcation in the Trailing Stream. This prediction is consistent with recent measurements of spatial variation in chemical abundances in the Leading Arm, which show that gas from multiple sources is present, although the nature is still uncertain.

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