发表机构
Tsinghua University; Leibniz-Institut für Astrophysik Potsdam; Institut für Theoretische Astrophysik, Zentrum für Astronomie, Universität Heidelberg; The University of Texas at Dallas; York University; University of Bologna; INAF, Astrophysics and Space Science Observatory Bologna; Columbia University; Northwestern University; Massachusetts Institute of Technology（清华大学; 波茨坦阿诺德·爱因斯坦天体物理研究所; 海德堡大学天体物理学中心理论天体物理研究所; 达拉斯德州大学; 约克大学; 博洛尼亚大学; 意大利国家天体物理研究所博洛涅空间科学天文台; 哥伦比亚大学; 西北大学; 麻省理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过RIGEL模拟揭示非均匀宇宙再电离通过两阶段过程抑制恒星形成，并发现再电离时暗物质晕质量是决定超微弱矮星系多样性（恒星质量、年龄分布和化学演化）的关键参数。
AI 中文摘要
超微弱矮星系（UFDs）是宇宙中最小、最古老的星系之一，被广泛视为宇宙再电离的遗迹。为了研究再电离如何抑制恒星形成并塑造超微弱矮星系的多样性，我们展示了一套包含八个宇宙学zoom-in模拟的星系样本，这些模拟针对当前暗物质晕质量约为$\sim10^9\\,{\rm M}_\odot$的孤立超微弱矮星系。模拟采用辐射磁流体动力学星系形成框架——星系演化与生命周期中的真实星际介质建模（RIGEL），并耦合了从THESAN再电离模拟中提取的真实大尺度辐射场。尽管这些模拟星系位于相似的$z=0$暗物质晕中，它们的恒星质量跨越了近两个数量级，并大致重现了本星系群超微弱矮星系的观测光度、大小、金属丰度和恒星运动学特征。我们发现再电离通过两阶段过程抑制恒星形成。电离前沿的到来迅速光电离弥散的环星系介质和星系际介质，抑制了气体向星系的进一步吸积。然而，恒星形成仍利用存留的自屏蔽气体储库持续了数亿年，直到这些气体被消耗或消散后才停止。在再电离后500 Myr内，暗物质晕中剩余的气体质量不足初始气体质量的40%，其中光致蒸发是主导的气体损失通道。我们进一步表明，再电离时的暗物质晕质量是控制超微弱矮星系后续演化的关键参数。再电离时位于更大质量暗物质晕中的星系能更长时间保留气体，并进行更长时间的化学增丰。因此，再电离时的暗物质晕质量与星系最终的恒星质量、恒星年龄分布和化学演化密切相关。
英文摘要
Ultra-faint dwarf galaxies (UFDs) are among the smallest and oldest galaxies in the Universe and are widely regarded as relics of cosmic reionization. To investigate how reionization quenches star formation and shapes the diversity of UFDs, we present a suite of eight cosmological zoom-in simulations of isolated UFDs with present-day halo masses of $\sim10^9\,{\rm M}_\odot$. The simulations are performed with the radiation-magnetohydrodynamic galaxy formation framework Realistic ISM modeling in Galaxy Evolution and Lifecycles (RIGEL), coupled to realistic large-scale radiation fields extracted from the THESAN reionization simulation. Despite residing in similar $z=0$ halos, the simulated galaxies span nearly two orders of magnitude in stellar mass and broadly reproduce the observed luminosities, sizes, metallicities, and stellar kinematics of Local Group UFDs. We find that reionization quenches star formation through a two-stage process. The arrival of the ionization front rapidly photoionizes the diffuse circumgalactic and intergalactic gas, suppressing further gas accretion onto the galaxy. Star formation nevertheless continues for several hundred Myr using the surviving self-shielded gas reservoir and ceases only after this gas is consumed or dispersed. Within 500 Myr after reionization, less than 40% of the initial gas mass remains in the halo, with photoevaporation constituting the dominant gas-loss channel. We further show that the halo mass at the time of reionization is a key parameter governing the subsequent evolution of UFDs. Galaxies residing in more massive halos at reionization retain gas for longer periods and undergo more extended chemical enrichment. Consequently, the halo mass at reionization strongly correlates with the final stellar mass, stellar age spread, and chemical evolution of the galaxy.
Comments18 pages, 14 figures, submitted to A&A
