解析再电离时期强 [O III] 发射体所推断恒星形成历史中的歧义
Resolving Ambiguities in the Inferred Star Formation Histories of Intense [O III] Emitters in the Reionisation Era
AI总结：
本研究利用 JWST 中波段近红外测光分离 [O III] 发射与 Balmer 跃变，发现部分 z≈8.2–8.6 强发射体年龄达 150 Myr 以上，表明其早在 z∼10 前已开始恒星形成。
摘要：
早期 JWST 光谱观测活动已证实，在红移区间 7<z<9 内存在强 [O III] 谱线发射星系。尽管此前由 Spitzer 测光推断这种现象指示年轻恒星族群，但一些研究提出，归因于 [O III] 发射的相关测光超差可能有一部分来自较老恒星产生的 Balmer 跃变。我们利用哈勃超深场中的 JWST 中波段近红外测光证明，情况很可能正是如此。我们定位了一个包含 6 个红移位于 8.2<z<8.6 的星系样本，相关中波段滤光片使我们能够分离 [O III] 发射与 Balmer 跃变的贡献，从而打破早期解释中的简并。该技术尤其有价值，因为它提供的测光红移精度达到 Δz ≃ ±0.08，接近目前 JWST 正在开展的光谱观测精度。尽管部分源较为年轻，但我们样本中有三分之一呈现显著 Balmer 跃变，与 ≥150 Myr 的恒星年龄相符。我们的结果表明，即使是强 [O III] 发射体，也经历过可追溯至 z∼10 乃至更高红移的早期恒星形成阶段；如今，通过直接探测类似系统的前身天体，人们也在独立得出这一结论。
英文摘要：
Early JWST spectroscopic campaigns have confirmed the presence of strong [O III] line-emitting galaxies in the redshift interval $7<z<9$. Although deduced earlier from Spitzer photometry as indicative of young stellar populations, some studies suggested the relevant photometric excesses attributed to [O III] emission could, in part, be due to Balmer breaks arising from older stars. We demonstrate that this is likely the case by exploiting medium-band near-infrared JWST photometry in the Hubble Ultra Deep Field. We locate a sample of 6 galaxies with redshifts 8.2$<z<$8.6 for which the relevant medium-band filters enables us to separate the contributions of [O III] emission and a Balmer break, thereby breaking earlier degeneracies of interpretation. The technique is particularly valuable since it provides photometric redshifts whose precision, $Δ\,z\simeq\,\pm0.08$, approaches that of spectroscopic campaigns now underway with JWST. Although some sources are young, a third of our sample have prominent Balmer breaks consistent with stellar ages of $\geq$150 Myr. Our results indicate that even intense [O III] emitters experienced episodes of earlier star formation to $z\sim$10 and beyond, as is now being independently deduced from direct detection of the progenitors of similar systems.
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