Wang Weichen, Cantalupo Sebastiano, Pensabene Antonio, Galbiati Marta, Travascio Andrea, Steidel Charles C, Maseda Michael V, Pezzulli Gabriele, de Beer Stephanie, Fossati Matteo, Fumagalli Michele, Gallego Sofia G, Lazeyras Titouan, Mackenzie Ruari, Matthee Jorryt, Nanayakkara Themiya, Quadri Giada
Department of Physics, Universita degli Studi di Milano-Bicocca, Milano, Italy.
Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA USA.
Nat Astron. 2025;9(5):710-719. doi: 10.1038/s41550-025-02500-2. Epub 2025 Mar 17.
Observational studies have shown that galaxy disks were already in place in the first few billion years of the Universe. The early disks detected so far, with typical half-light radii of 3 kpc at stellar masses around 10 for redshift ≈ 3, are significantly smaller than today's disks with similar masses, which is in agreement with expectations from current galaxy models. Here we report observations of a giant disk at = 3.25, when the Universe was only two billion years old, with a half-light radius of 9.6 kpc and stellar mass of . This galaxy is larger than any other kinematically confirmed disks at similar epochs and is surprisingly similar to today's largest disks with regard to size and mass. James Webb Space Telescope imaging and spectroscopy reveal its spiral morphology and a rotational velocity consistent with a local Tully-Fisher relationship. Multiwavelength observations show that it lies in an exceptionally dense environment, where the galaxy number density is more than ten times higher than the cosmic average and mergers are frequent. The discovery of such a giant disk suggests the presence of favourable physical conditions for large-disk formation in dense environments in the early Universe, which may include efficient accretion of gas carrying coherent angular momentum and non-destructive mergers between exceptionally gas-rich progenitor galaxies.
观测研究表明，星系盘在宇宙最初的几十亿年里就已形成。目前探测到的早期星系盘，在红移约为3时，典型的半光半径为3千秒差距，恒星质量约为10，其尺寸明显小于如今具有相似质量的星系盘，这与当前星系模型的预期相符。在此，我们报告了对一个红移为3.25时的巨大星系盘的观测，当时宇宙仅有20亿年历史，其半光半径为9.6千秒差距，恒星质量为 。这个星系比在相似时期任何其他通过运动学确认的星系盘都要大，并且在尺寸和质量方面与如今最大的星系盘惊人地相似。詹姆斯·韦布空间望远镜的成像和光谱分析揭示了它的螺旋形态以及与局部塔利-费舍尔关系相符的旋转速度。多波长观测表明，它处于一个异常密集的环境中，那里的星系数密度比宇宙平均水平高出十多倍，星系合并频繁。如此巨大星系盘的发现表明，在早期宇宙的密集环境中存在有利于大星系盘形成的物理条件，这可能包括携带相干角动量的气体的高效吸积以及富含气体的原星系之间的非破坏性合并。
