高红移贫金属星系中由FUV辐射反馈诱发的剧烈星暴与宁静期
Violent starbursts and quiescence induced by FUV radiation feedback in metal-poor galaxies at high-redshift
AI总结：
本文通过高分辨率宇宙学辐射流体力学模拟发现，来自Pop II恒星的FUV辐射抑制冷却是触发高红移贫金属星系剧烈星暴的核心机制，导致星系异常明亮并随后进入长期熄灭状态。
摘要：
JWST对$z\gtrsim 8$星系的观测表明，它们比大多数模型的预测更亮且更团块化，这促使人们针对第一批星系的恒星形成与反馈物理提出了若干假说。本文通过在亚pc分辨率下对单个星系进行一系列采用不同辐射反馈模型的宇宙学辐射流体动力学模拟，重点研究紫外（UV）辐射在调节恒星形成中的作用。我们发现，来自Pop II恒星的远紫外（FUV）辐射（即$\mathrm{H_2}$解离辐射）对冷却的抑制，是触发致密大质量星团形成的主要物理过程，并导致了$z\gtrsim 10$贫金属星系中观测到的爆发性恒星形成。事实上，人为抑制FUV辐射会导致一种较不强烈的连续恒星形成模式，恒星分布在众多但低质量的疏散星团中。由于强烈的FUV场，低金属丰度云团保持温暖（$\sim 10^4\\,\mathrm{K}$），直到达到相对较高的密度（$\gtrsim 10^3\\,\mathrm{cm^{-3}}$），随后才变得自屏蔽并转变为较冷（$\sim 100\\,\mathrm{K}$）的部分分子相。因此，恒星形成被延迟，直到云团积累足够质量以变得引力不稳定。此时，云团经历快速恒星形成，以高效率将气体转化为恒星。因此，我们观测到异常明亮的星系（比连续恒星形成亮十倍），以及随后数千万年未形成恒星的熄灭“死亡”星系。
英文摘要：
JWST observations of galaxies at $z\gtrsim 8$ suggest that they are more luminous and clumpier than predicted by most models, prompting several proposals on the physics of star formation and feedback in the first galaxies. In this paper, we focus on the role of ultraviolet (UV) radiation in regulating star formation by performing a set of cosmological radiation hydrodynamics simulations of one galaxy at sub-pc resolution with different radiative feedback models. We find that the suppression of cooling by far UV (FUV) radiation (i.e., $\mathrm{H_2}$ dissociating radiation) from Pop II stars is the main physical process triggering the formation of compact and massive star clusters and is responsible for the bursty star formation observed in metal-poor galaxies at $z\gtrsim 10$. Indeed, artificially suppressing FUV radiation leads to a less intense continuous mode of star formation distributed into numerous, but low-mass open star clusters. Due to the intense FUV field, low-metallicity clouds remain warm ($\sim 10^4\,\mathrm{K}$) until they reach a relatively high density ($\gtrsim 10^3\,\mathrm{cm^{-3}}$), before becoming self-shielded and transitioning to a colder ($\sim 100\,\mathrm{K}$), partially molecular phase. As a result, star formation is delayed until the clouds accumulate enough mass to become gravitationally unstable. At this point, the clouds undergo rapid star formation converting gas into stars with high efficiency. We, therefore, observe exceptionally bright galaxies (ten times brighter than for continuous star formation) and subsequent quenched "dead" galaxies that did not form stars for tens of Myrs.
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