发表机构
University of Washington; University of Pittsburgh; University of Colorado, Boulder; University of California, Santa Cruz; Princeton University（华盛顿大学; 匹兹堡大学; 科罗拉多大学博尔德分校; 加州大学圣克鲁兹分校; 普林斯顿大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究基于JWST UNCOVER+MegaScience巡天数据，利用Prospector模型识别红移4-7处的小型淬灭“小憩”星系，证实仅测光可可靠识别该类星系，发现其在低质量星系中最普遍，为宇宙学模拟提供观测检验平台。
AI 中文摘要
我们在UNCOVER/MegaScience巡天的光谱和测光样本中，探究了小型淬灭（或称“小憩”）星系的普遍存在性。这类星系通过中等强度的巴耳末断裂、弱发射线（EW(Hα) < 100埃）以及相对偏蓝的紫外连续谱被经验性地识别。我们使用灵活的非参数模型Prospector推断样本的恒星形成历史（SFHs），优化以捕捉近期的爆发恒星形成和淬灭事件，发现这类星系在SFR₁₀/SFR₁₀₀参数空间中向（临时）宁静态移动，具有独特的可识别性。我们证实，尽管光谱最适合识别快速下降的恒星形成率（SFR），但密集采样的中波段测光可恢复这些关键光谱特征，从而仅通过成像就能可靠识别该暂态的纯样本。我们在阿贝尔2744引力透镜场中量化了红移z=4-7处“小憩”星系的数密度，发现8个经光谱确认的“小憩”星系和60个测光候选体，其恒星质量对数log₁₀(M*/M☉)范围为7.5-10。我们利用较小的高信噪比光谱样本验证，仅测光就能识别出纯的“小憩”星系样本。与此前研究一致，我们发现“小憩”星系在低恒星质量（log₁₀(M*/M☉) ~9）处最为常见。我们观测到数密度从z~6到z~4有增加的趋势，但小样本可能受宇宙方差影响。本研究表明，随机恒星形成作为再电离后数亿年低质量星系增长的调控因素，其重要性日益提升，为宇宙学模拟中恒星反馈的强度和占空比提供了直接的观测检验平台。
英文摘要
We explore the prevalence of mini-quenched or ``napping'' galaxies selected from spectroscopic and photometric samples in the UNCOVER/MegaScience survey. These galaxies are empirically identified by the presence of moderate Balmer breaks, weak emission lines ($EW(Hα) < 100$A) and relatively blue UV continua. We infer the star formation histories (SFHs) of our sample using flexible non-parametric models with Prospector optimized to capture recent episodes of bursty star formation and quenching, and find that they are uniquely identifiable in the SFR$_{10}$/SFR$_{100}$ parameter space moving towards (temporary) quiescence. We demonstrate that although spectroscopy is best able to identify rapidly declining SFRs, densely sampled medium-band photometry recover these key spectral features and thus robustly identify pure samples of this transient phase -- with imaging alone. We quantify the number density of napping galaxies at $z=4-7$ in the Abell 2744 lensing field, finding 8 spectroscopically confirmed nappers and 60 photometric candidates spanning log$_{10}$(M$_*$/M$_\odot$) $= 7.5-10$. We verify that the photometry alone can identify a pure sample of nappers, leveraging a smaller high signal-to-noise ratio spectroscopic sample. Consistent with previous studies, we find that nappers are most common at low stellar mass (log$_{10}$(M$_*$/M$_\odot$) $\sim9$). We see a hint that the number densities increase from $z\sim6$ to $z\sim4$, though our small sample is likely affected by cosmic variance. Our study demonstrates the increasing importance of stochastic star formation as a regulator of low-mass galaxy growth in the several hundred Myr after reionization, and offers a direct observational testbed for the strength and duty cycle of stellar feedback in cosmological simulations.
Comments30 pages, 12 figures, 3 tables; submitted to ApJ
