The hierarchical structure formation of our Universe inherently involves disruptive and chaotic episodes of mass assembly such as galaxy mergers. The level of bulk rotation of the collisionless stellar systems of galaxies reflects to what extent the galaxies, on the other hand, have assembled their stars during tranquil and ordered formation history, which fosters the growth of cohesively rotating structures. Observationally, galaxy populations show a wide spectrum of morphology and shapes, with different levels of rotational support. Despite the obvious variety and complexity, in this work we find that, at a given stellar mass of galaxies, the distribution of the intrinsic spin parameter \({\lambda }_{{R}_{{{\rm{e}}}},{{\rm{intr}}}}\), that is, the normalized specific angular momentum of stars, appears to be universally bimodal among galaxies in all star-formation states and also in different environments. This ubiquitous bimodality in kinematic morphology evolves systematically with star formation and is particularly apparent for transitional galaxies of intermediate star-formation rates, which indicates that star-formation quenching is proceeding separately within two distinct kinematic populations dominated by cold disks and hot spheroids. We show that the two populations also have contrasting recent star-formation histories and metal-enrichment histories, which reveal their divergent pathways to formation and quenching.

我们宇宙的层次结构的形成本质上涉及质量组装的破坏性和混乱的事件，例如星系合并。另一方面，星系的无碰撞恒星系统的整体旋转水平反映了星系在平静和有序的形成历史中聚集恒星的程度，这促进了粘性旋转结构的生长。通过观察，星系群表现出广泛的形态和形状，并具有不同程度的旋转支持。尽管存在明显的多样性和复杂性，但在这项工作中我们发现，在给定的星系恒星质量下，固有自旋参数的分布\({\lambda }_{{R}_{{{\rm{e}} }},{{\rm{intr}}}}\) ，即恒星的归一化比角动量，在所有恒星形成状态以及不同环境下的星系中似乎普遍呈双峰。这种运动学形态中普遍存在的双峰性随着恒星形成而系统地演化，对于中等恒星形成率的过渡星系尤其明显，这表明恒星形成猝灭是在以冷盘和热球体为主的两个不同的运动群中分别进行的。我们表明，这两个族群还具有对比的近期恒星形成历史和金属富集历史，这揭示了它们形成和淬灭的不同途径。