无反馈效率极限边缘的大质量星系
A Massive Galaxy at the Edge of Feedback-Free Efficiency
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中文总结 AI 辅助
该研究通过观测z=9.31的星系UNCOVER 3686，首次检验宇宙黎明时期无反馈星暴（FFB）星系的重子转化效率，发现其效率达20%-60%，接近理论极限，是FFB星系的极佳候选。
中文摘要 AI 辅助
星系将可用重子库转化为恒星的效率，为早期宇宙恒星质量组装设定了基本上限，且编码了恒星反馈的累积效应。本文报告了对z=9-10的一个经测光和光谱验证的参考样本的恒星形成效率（SFE）的测量结果，其中31个得到光谱确认。我们重点关注其中一个光谱确认的星系——z=9.31的\texttt{UNCOVER 3686}，其恒星质量$M_\bigstar=10^{9.55}$M$_\bigodot$，物理性质与无反馈星暴（FFB）情景的预测相符。我们以该星系为基准，首次直接观测检验宇宙黎明时期具有FFB理论预测物理性质的星系是否达到无反馈星暴情景预测的最大重子转化效率。我们发现该星系的SFE介于约20%至60%之间，比经验模型预测值高2至6倍。该星系的致密形态（$R_e=0.45$kpc）、年轻恒星年龄（约160Myr）、低金属丰度（$Z_\bigstar/Z_\bigodot\thickapprox0.2$）以及推断的气体密度（$n_{\rm gas}\thicksim3\times10^3$cm$^{-3}$）均与无反馈（FFB）星系形成条件一致。我们得出结论，UNCOVER 3686是FFB星系的极佳候选体，其全局恒星形成效率因恒星反馈微弱而接近理论极限。
英文摘要
The efficiency with which galaxies convert their available baryonic reservoir into stars sets a fundamental ceiling on stellar mass assembly in the early Universe and encodes the cumulative effect of stellar feedback. in this paper, we report the measurement of star-formation efficiency (SFE) of a photometrically and spectroscopically vetted reference sample at $z=9-10$, out of which 31 are spectroscopically confirmed. Among them, we highlight a spectroscopically confirmed galaxy, \texttt{UNCOVER 3686} at $z = 9.31$, which has a stellar mass $M_\star = 10^{9.55}$ M$_\odot$ and physical properties comparable to the predictions of the feedback-free starburst (FFB) scenario. We use this galaxy as an anchor for the first direct observational test of whether galaxy at cosmic dawn with physical properties predicted in the FFB theory reach the maximum baryon conversion efficiencies predicted by the feedback-free starburst scenario. We find the SFE for this galaxy to lie between $\approx 20\%$ and $60\%$, a factor of 2 to 6 above empirical model predictions. The compact morphology ($R_e = 0.45$ kpc), young stellar age ($\sim 160$ Myr), low metallicity $(Z_\star/Z_\odot \approx 0.2)$, and inferred gas density $(n_{\rm gas} \sim 3\times 10^{3}$ cm$^{-3}$) of this galaxy are consistent with feedback-free (FFB) galaxy formation conditions. We conclude that UNCOVER 3686 is an excellent candidate for an FFB galaxy in which the global star formation efficiency approaches the theoretical limits due to weak stellar feedback.
