Cosmological models predict that galaxies forming in the early Universe experience a chaotic phase of gas accretion and star formation, followed by gas ejection due to feedback processes. Galaxy bulges may assemble later via mergers or internal evolution. Here we present submillimeter observations (with spatial resolution of 700 parsecs) of ALESS 073.1, a starburst galaxy at redshift z≃5 when the Universe was 1.2 billion years old. This galaxy’s cold gas forms a regularly rotating disk with negligible noncircular motions. The galaxy rotation curve requires the presence of a central bulge in addition to a star-forming disk. We conclude that massive bulges and regularly rotating disks can form more rapidly in the early Universe than predicted by models of galaxy formation.

宇宙学模型预测，在早期宇宙中形成的星系会经历气体积聚和恒星形成的混沌阶段，然后由于反馈过程而导致气体喷出。星系凸起可能会在以后通过合并或内部演变而组装。在这里，我们介绍ALESS 073.1（在红移时的星爆星系）的亚毫米观测（具有700帕秒的空间分辨率）ž≃5当宇宙有十二亿年历史的时候 这个银河系的冷气体形成一个规则的旋转圆盘，可忽略不计的非圆周运动。银河系旋转曲线除了需要形成恒星的圆盘外，还需要中央凸起。我们得出的结论是，在宇宙早期，巨大的凸起和规则旋转的圆盘比银河系形成模型所预测的更快。