旧星系盘难消亡：AGN反馈如何抑制银河系质量星系中的星系盘形成？
Old Disks Die Hard: How Does AGN Feedback Suppress Disk Formation in Milky Way Mass Galaxies?
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中文总结 AI 辅助
本研究通过FIRE-2模拟分析银河系质量暗晕，发现AGN反馈在星系盘形成后生效，优先抑制薄星系盘恒星形成，使星系形成椭球占比更高的透镜星系。
中文摘要 AI 辅助
星系的视觉形态与恒星形成率之间的关联是星系演化领域最古老的已确立趋势之一，但该趋势的起源仍未明确。我们分析了两个采用FIRE-2星系形成物理模拟的银河系质量暗晕，每个暗晕分别在无AGN以及最多三种AGN反馈实现方案下运行，借此研究AGN的恒星形成抑制如何以及为何在宇宙时标上影响形态演化。所有无AGN反馈的模拟在z=0时均形成了显著的、薄的、正在形成恒星的旋涡星系盘；而每个AGN模拟的后期恒星形成更少，最终具有更高的椭球星系成分占比和更低的薄星系盘质量占比，其中两个AGN模拟在z=0时形成了无冷气体的 quenched 透镜星系。这些形态差异的主要原因是，在所有模拟中，AGN反馈均在星系盘形成启动后、即“自旋加速”阶段变得有效；这种时间差异化的影响会优先抑制星系盘恒星，尤其是薄星系盘恒星的形成，因为薄星系盘的形成发生在后期。而椭球成分在所有模拟中均在AGN反馈生效之前就已形成，因此不同模拟间的椭球质量和大小相似。
英文摘要
The connection between a galaxy's visual shape and its star formation rate is one of the oldest established trends in galaxy evolution, yet the origin of this trend remains unsettled. We analyze two Milky-Way mass halos simulated with FIRE-2 galaxy formation physics, each run without AGN and with up to three implementations of AGN feedback. We use them to study how and why AGN star formation suppression affects morphological evolution over cosmic time. Both runs without AGN feedback produce prominent, thin, star-forming spiral disks at $z=0$. Each of the AGN runs has less late-time star formation, and ends up with a higher spheroid fraction and a lower thin-disk mass fraction. In two instances, the AGN runs produce quenched lenticular galaxies with no cool gas at $z=0$. The main reason for these morphological differences is that AGN feedback becomes effective {\em just after} the onset of disk formation, at ``spin up," in every run. This time-differentiated impact suppresses the formation of disk stars, especially thin-disk stars, preferentially because thin-disk formation occurs late. The spheroidal components are assembled early in all runs, before AGN feedback is effective, and are therefore similar in mass and size across runs.
