近日，英国剑桥大学的Tobias J. Looser及其研究团队取得一项新进展。经过不懈努力，他们发现大爆炸后7亿年一个近期猝灭的星系。相关研究成果已于2024年3月6日在国际权威学术期刊《自然》上发表。

该研究团队披露了宇宙年龄仅7亿年时，在z=7.3位置发现的一个（迷你）淬灭星系。该星系的光谱由JWST/NIRSpec测得，显示为非常蓝的色调（UV = 0.16±0.03星等），尽管它表现出了巴尔默断裂，但并未观测到星云发射线。据分析，这个星系经历了一段短暂的星爆后迅速进入了淬灭阶段；其恒星质量约为4-6×10⁸ M_⊙，这个质量范围对各种反馈机制都极为敏感，这可能只导致了星系暂时的淬灭。

据悉，已知局部和低红移(z<3)星系大致遵循双峰分布：恒星形成速度相对稳定的活动恒星形成星系和被动系统。这两个星系族是由相对缓慢过渡的星系连接起来的。相反，理论预测，在早期宇宙时期和低质量系统中，恒星的形成是随机的：这些星系在星爆事件和受抑制的恒星形成阶段之间迅速过渡，甚至可能导致暂时的静止——所谓的迷你猝灭事件。然而，恒星形成爆发的机制在观测上是高度不受约束的。因此，直接观测原始宇宙中的微淬灭星系对于约束星系形成和转化模型至关重要。早期被淬灭的星系已被确认为红移z<5的范围内的天体，这些星系都是大质量星系（M_*> 10¹⁰ M_⊙），且相对较老。

附：英文原文

Title: A recently quenched galaxy 700 million years after the Big Bang

Author: Looser, Tobias J., DEugenio, Francesco, Maiolino, Roberto, Witstok, Joris, Sandles, Lester, Curtis-Lake, Emma, Chevallard, Jacopo, Tacchella, Sandro, Johnson, Benjamin D., Baker, William M., Suess, Katherine A., Carniani, Stefano, Ferruit, Pierre, Arribas, Santiago, Bonaventura, Nina, Bunker, Andrew J., Cameron, Alex J., Charlot, Stephane, Curti, Mirko, de Graaff, Anna, Maseda, Michael V., Rawle, Tim, Rix, Hans-Walter, Del Pino, Bruno Rodrguez, Smit, Renske, bler, Hannah, Willott, Chris, Alberts, Stacey, Egami, Eiichi, Eisenstein, Daniel J., Endsley, Ryan, Hausen, Ryan, Rieke, Marcia, Robertson, Brant, Shivaei, Irene, Williams, Christina C., Boyett, Kristan, Chen, Zuyi, Ji, Zhiyuan, Jones, Gareth C., Kumari, Nimisha, Nelson, Erica, Perna, Michele, Saxena, Aayush, Scholtz, Jan

Issue&Volume: 2024-03-06

Abstract: Local and low-redshift (z<3) galaxies are known to broadly follow a bimodal distribution: actively star forming galaxies with relatively stable star-formation rates, and passive systems. These two populations are connected by galaxies in relatively slow transition. In contrast, theory predicts that star formation was stochastic at early cosmic times and in low-mass systems: these galaxies transitioned rapidly between starburst episodes and phases of suppressed star formation, potentially even causing temporary quiescence –so-called mini-quenching events . However, the regime of star-formation burstiness is observationally highly unconstrained. Directly observing mini-quenched galaxies in the primordial Universe is therefore of utmost importance to constrain models of galaxy formation and transformation. Early quenched galaxies have been identified out to redshift z < 5, and these are all found to be massive (M_*> 10¹⁰ M_⊙) and relatively old. Here we report a (mini-)quenched galaxy at z=7.3, when the Universe was only 700 Myr old. The JWST/NIRSpec spectrum is very blue (UV =0.16 ± 0.03 mag), but exhibits a Balmer break and no nebular emission lines. The galaxy experienced a short starburst followed by rapid quenching; its stellar mass (4-6×10⁸ M_⊙) falls in a range that is sensitive to various feedback mechanisms, which can result in perhaps only temporary quenching.

DOI: 10.1038/s41586-024-07227-0

Source: https://www.nature.com/articles/s41586-024-07227-0