We discuss the spectral energy distributions and physical properties of six galaxies whose photometric redshifts suggest they lie beyond a redshift z ≃ 9. Each was selected on account of a prominent excess seen in the Spitzer/IRAC 4.5 $\mu$m band which, for a redshift above z = 9.0, likely indicates the presence of a rest-frame Balmer break and a stellar component that formed earlier than a redshift z ≃ 10. In addition to constraining the earlier star formation activity on the basis of fits using stellar population models with BAGPIPES, we have undertaken the necessary, but challenging, follow-up spectroscopy for each candidate using various combinations of Keck/MOSFIRE, VLT/X-shooter, Gemini/FLAMINGOS2, and ALMA. Based on either Lyman-α or [O iii] 88 $\mu$m emission, we determine a convincing redshift of z = 8.78 for GN-z-10-3 and a likely redshift of z = 9.28 for the lensed galaxy MACS0416-JD. For GN-z9-1, we conclude the case remains promising for a source beyond z ≃ 9. Together with earlier spectroscopic data for MACS1149-JD1, our analysis of this enlarged sample provides further support for a cosmic star formation history extending beyond redshifts z ≃ 10. We use our best-fitting stellar population models to reconstruct the past rest-frame UV luminosities of our sources and discuss the implications for tracing earlier progenitors of such systems with the James Webb Space Telescope.

中文翻译：

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探索宇宙黎明：候选 z ≥ 9 星系的年龄和恒星形成历史

我们讨论了六个星系的光谱能量分布和物理特性，这些星系的光度学红移表明它们位于红移 z ≃ 9 之外。每个星系的选择都是因为在 Spitzer/IRAC 4.5 $\mu$m 波段中看到的显着过剩，对于高于 z = 9.0 的红移，可能表明存在静止框架 Balmer 断裂和早于红移 z ≃ 10 形成的恒星成分。除了基于使用恒星群模型的拟合来限制早期恒星形成活动之外通过 BAGPIPES，我们使用 Keck/MOSFIRE、VLT/X-shooter、Gemini/FLAMINGOS2 和 ALMA 的各种组合对每个候选者进行了必要但具有挑战性的后续光谱。基于 Lyman-α 或 [O iii] 88 $\mu$m 发射，我们确定了令人信服的 z = 8 红移。GN-z-10-3 为 78，透镜星系 MACS0416-JD 的红移可能为 z = 9.28。对于 GN-z9-1，我们得出结论认为，对于 z ≃ 9 以外的源，这种情况仍然很有希望。连同 MACS1149-JD1 的早期光谱数据，我们对这个放大样本的分析为超越红移 z 的宇宙恒星形成历史提供了进一步的支持≃ 10. 我们使用我们最适合的恒星种群模型来重建我们光源过去的静止框架紫外光度，并讨论使用詹姆斯韦伯太空望远镜追踪此类系统的早期祖先的意义。