AI 中文总结
研究高红移矮星系过冷却问题，通过宇宙学模拟采用施密特型和基于吸积汇的恒星形成模型，发现后者能产生爆发性恒星形成，增强反馈，缓解过冷却，在恒星质量、逃逸率及外流等方面表现更好，与观测更相符。
AI 中文摘要
恒星形成是星系演化的基本驱动力，但许多星系形成模型仍无法现实地调节它，导致气体过度坍缩并产生过多恒星。为研究过冷却问题的可能解决方案，我们对一个在z = 6时质量达10¹⁰M☉的暗物质晕进行了宇宙学放大辐射流体动力学模拟，采用两种不同的恒星形成模型：施密特型模型，其中恒星形成标准和每个自由落体时间的效率与局部引力 - 热 - 湍流条件相关；基于吸积汇的模型，其中恒星形成由局部气体流入控制。基于吸积汇的模型通过快速吸积到嵌入强汇聚气流中的年轻吸积汇粒子上自然产生爆发性恒星形成。在第一次超新星爆发之前，产生的强烈辐射通过光电离加热使恒星形成团块电离并分散。因此，超新星在低密度环境中发生，赋予更大的终端动量并驱动更强的星系外流。相比之下，在施密特型模型中，单个气体团块内的恒星形成效率较低，因为单个恒星形成事件会局部改变细胞条件，暂时抑制后续恒星形成并降低爆发程度。到z = 6时，基于吸积汇的模型相对于施密特型模型，总恒星质量低约3倍，莱曼连续谱逃逸率高约10倍。爆发性模型驱动更强的富含金属的外流并抑制中心恒星形成过剩，在气相金属丰度和星系大小方面与JWST观测结果表现出更好的一致性。我们的结果表明，爆发性恒星形成是增强反馈和缓解星系形成模拟中过冷却问题的关键机制。
英文摘要
Star formation is a fundamental driver of galaxy evolution, yet many galaxy formation models still fail to regulate it realistically, allowing gas to collapse too efficiently and overproduce stars. To investigate a possible solution to this overcooling problem, we perform cosmological zoom-in radiation-hydrodynamics simulations of a dark matter halo reaching $10^{10} M_\odot$ at $z=6$, adopting two distinct star formation models: a Schmidt-type model, in which star formation criteria and efficiency per free-fall time are tied to local gravo-thermo-turbulent conditions, and a sink-based model, in which star formation is governed by local gas inflows. The sink-based model naturally produces bursty star formation through rapid accretion onto young sink particles embedded in strongly convergent gas flows. The resulting intense radiation ionizes and disperses star-forming clumps through photoionization heating before the first supernova explodes. Consequently, supernovae occur in lower-density environments, imparting greater terminal momentum and driving stronger galactic outflows. In contrast, star formation within individual gas clumps is less efficient in the Schmidt-type model, because individual star formation events locally modify cell conditions, temporarily suppressing subsequent star formation and lowering the degree of burstiness. Relative to the Schmidt-type model, the sink-based model yields a total stellar mass lower by a factor of $\sim3$ and a Lyman continuum escape fraction higher by a factor of $\sim10$ by $z=6$. The bursty model drives stronger metal-enriched outflows and suppresses excess central star formation, exhibiting better agreement with JWST observations in gas-phase metallicity and galaxy size. Our results suggest that bursty star formation is a key mechanism for enhancing feedback and alleviating the overcooling problem in galaxy formation simulations.
Comments24 pages, 23 figures, submitted to A&A
