标题： 宇宙15亿年间作为熄火机制的喷出反馈：在一颗最近熄火的星系中探测到中性气体外流$z=4$ 显示英文标题

标题： Ejective feedback as a quenching mechanism in the 1.5 billion years of the universe: detection of neutral gas outflow in a $z=4$ recently quenched galaxy

摘要： 宇宙初期就存在大质量平静星系的确认引发了关于星系形成机制的有趣问题。 一定有非常高效的过程在起作用，以在宇宙黎明时关闭星系中的恒星形成。 我报告了在$z=4$处检测到一个大质量近期平静星系中的中性外流气体，显示排斥作为平静机制。 基于 JWST 光谱，这个星系的恒星形成率正在以快速 e 折叠时间尺度为$\sim50$百万年下降。 当前的具体恒星形成率是$5\times10^{-11}$每年每秒$^{-1}$，大约比同等红移下的恒星形成主序列低 40 倍。 [NeIII]/[OII] 和 [OIII]/H$\beta$的发射线比率与同等红移下的活动星系核 (AGN) 类似。 一系列 FeII 和 MgII 吸收线相对于恒星连续谱蓝移了$\sim250$~km~s$^{-1}$，表明中性气体外流。 估计的质量外流率大约是来自恒星连续谱的恒星形成率的 7 倍，这意味着恒星形成的抑制可能由于流出导致的气体耗尽。 如果发射线是由 AGN 驱动的，AGN 也可以提供足够的能量来启动观测到的外流。 这个星系代表了迄今为止已知最遥远的同类例子。 本研究为宇宙最初十亿年内存在大质量平静星系提供了令人信服的解释。 显示英文摘要

摘要： The confirmation of massive quiescent galaxies emerging within the first billion years of the universe poses intriguing questions about the mechanisms of galaxy formation. There must be highly efficient processes at work to shut down star formation in galaxies at cosmic dawn. I present the detection of neutral outflowing gas in a massive recently quenched galaxy at $z=4$, showing ejective back as a quenching mechanism. Based on JWST spectrum, the star formation rate of this has been declining with a rapid e-folding timescale of $\sim50$ Myrs. The current specific star formation rate is $5\times10^{-11}$ yr$^{-1}$, roughly 40 times lower than that of the star-forming main sequence at comparable redshifts. Emission line ratios of [NeIII]/[OII] and [OIII]/H$\beta$ are similar to AGN at comparable redshifts. A series of FeII and MgII absorption lines appear blueshifted by $\sim250$~km~s$^{-1}$ relative to the stellar continuum, suggesting an outflow of neutral gas. The estimated mass outflow rate is approximately 7 times greater than the star formation rate derived from the stellar continuum, implying that the suppression of star formation is likely due to gas being depleted by the outflow. If the emission lines are AGN-driven, the AGN can also provide sufficient energy to launch the outflow observed. This galaxy represents the most distant example of its kind known to date. This study offers a compelling explanation for the existence of massive quiescent galaxies in the first billion years of the universe.