Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria, Australia.
IBEX Innovations, Stockton-on-Tees, UK.
Nature. 2024 Apr;628(8007):277-281. doi: 10.1038/s41586-024-07191-9. Epub 2024 Feb 14.
The formation of galaxies by gradual hierarchical co-assembly of baryons and cold dark matter halos is a fundamental paradigm underpinning modern astrophysics and predicts a strong decline in the number of massive galaxies at early cosmic times. Extremely massive quiescent galaxies (stellar masses of more than 10 M) have now been observed as early as 1-2 billion years after the Big Bang. These galaxies are extremely constraining on theoretical models, as they had formed 300-500 Myr earlier, and only some models can form massive galaxies this early. Here we report on the spectroscopic observations with the JWST of a massive quiescent galaxy ZF-UDS-7329 at redshift 3.205 ± 0.005. It has eluded deep ground-based spectroscopy, it is significantly redder than is typical and its spectrum reveals features typical of much older stellar populations. Detailed modelling shows that its stellar population formed around 1.5 billion years earlier in time (z ≈ 11) at an epoch when dark matter halos of sufficient hosting mass had not yet assembled in the standard scenario. This observation may indicate the presence of undetected populations of early galaxies and the possibility of significant gaps in our understanding of early stellar populations, galaxy formation and the nature of dark matter.
星系通过重子和冷暗物质晕逐级共装配形成，这是现代天体物理学的基础范例，它预测早期宇宙中大质量星系的数量会急剧减少。现在已经观测到极其巨大的静止星系（恒星质量超过 10M）早在大爆炸后 10 到 20 亿年就已经形成。这些星系对理论模型极具限制，因为它们在 300 到 500 百万年前就已经形成，只有一些模型能够在这么早的时期形成大质量星系。在这里，我们报告了对 ZF-UDS-7329 这一大质量静止星系在红移 3.205 ± 0.005 处的 JWST 光谱观测结果。该星系躲过了深度的地面光谱观测，它比典型星系红得多，其光谱显示出更古老恒星种群的特征。详细的模型表明，其恒星种群大约在 15 亿年前（z ≈ 11）形成，当时在标准情景下，还没有足够的宿主质量的暗物质晕来组装星系。这一观测结果可能表明存在尚未被探测到的早期星系种群，并且我们对早期恒星种群、星系形成和暗物质本质的理解可能存在重大空白。
