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arXiv 2512.09030astro-ph.GA
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高红移气体丰盛盘中恒星径向迁移速率的增强

Enhanced rates of stellar radial migration in gas-rich discs at high redshift

University of Cambridge(剑桥大学);University of Sydney(悉尼大学);Kavli Institute for the Physics and Mathematics of the Universe(宇宙物理与数学柯尔菲研究所);University College London(伦敦大学学院);Lund University(隆德大学)

HanYuan Zhang, Thor Tepper-García, Vasily Belokurov, N. Wyn Evans, Takafumi Tsukui, Hillary Davis, Joss Bland-Hawthorn, Jason L. Sanders, Oscar Agertz

AI总结:

研究高红移气体丰盛盘中恒星径向迁移增强机制,揭示气体对盘内动力学加热和混合的影响,发现气体丰盛盘中恒星角动量变化更大,导致更强的径向混合。

摘要:

径向迁移和动力学加热在银河盘内重新分布恒星,从而改变宿主星系的化学-动力学结构。通常,这些长期过程在银河系类比的N体和流体动力学模拟中研究,这些模拟具有恒星主导的盘。相反,高红移盘富含气体,这可能改变长期演化的进程。我们使用Nexus框架构建并演化一系列孤立星系,其暗物质晕和盘质量固定,但初始盘气体分数从0%到100%变化。我们发现,在气体丰富的模型中,恒星角动量平方根变化比气体贫乏的模型大一倍,并伴有更强的径向和垂直加热,导致增强的径向混合。我们进一步分析气体在特定迁移通道中的作用。在棒驱动迁移中,共转共振拖拽主导于气体贫乏盘,而在气体丰富的盘中,恒星更易到达并积累在外侧 Lindblad 共振,这起着屏障作用。气体丰富的阶段中高径向混合效率可以仅在几个轨道时间尺度内使恒星金属licity梯度趋于平坦。这些结果表明,早期气体丰富的盘中的径向混合比晚期气体贫乏的盘更剧烈,自然产生化学双模盘的不同演化轨迹,如银河系。

英文摘要:

Radial migration and dynamical heating redistribute stars within galactic discs and thereby modify the chemo-kinematic structure of their host galaxies. Usually, these secular processes are studied in N-body and hydrodynamical simulations of Milky Way analogues with stellar-dominated discs. In contrast, discs at high redshift are gas-rich, which may qualitatively change how secular evolution proceeds. We use the Nexus framework to construct and evolve a suite of isolated galaxies with fixed halo and disc mass but varying initial disc gas fraction, from 0% to 100%. We show that in gas-rich models, the root-mean-square change in stellar angular momentum is up to a factor of two larger than in gas-poor analogues and is accompanied by stronger radial and vertical heating, leading to enhanced radial mixing. We further dissect the role of gas in specific migration channels. For bar-driven migration, corotation resonance dragging dominates in gas-poor discs, whereas in gas-rich discs, stars more readily reach and accumulate at the outer Lindblad resonance, which acts as a barrier. The high radial mixing efficiency in gas-rich phases can flatten the stellar metallicity gradient relative to that of the initial gaseous disc within only a few orbital timescales. Together, these results imply that radial mixing in early, gas-rich discs is substantially more vigorous than in late-time, gas-poor discs, naturally producing distinct evolutionary tracks for chemically bimodal discs such as that of the Milky Way.

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