We recently developed an automated method, auto-GMM to decompose simulated galaxies. It extracts kinematic structures in an accurate, efficient, and unsupervised way. We use auto-GMM to study the stellar kinematic structures of disk galaxies from the TNG100 run of IllustrisTNG. We identify four to five structures that are commonly present among the diverse galaxy population. Structures having strong to moderate rotation are defined as cold and warm disks, respectively. Spheroidal structures dominated by random motions are classified as bulges or stellar halos, depending on how tightly bound they are. Disky bulges are structures that have moderate rotation but compact morphology. Across all disky galaxies and accounting for the stellar mass within 3 half-mass radii, the kinematic spheroidal structures, obtained by summing up stars of bulges and halos, contribute ~45% of the total stellar mass, while the disky structures constitute 55%. This study also provides important insights about the relationship between kinematically and morphologically derived galactic structures. Comparing the morphology of kinematic structures with that of traditional bulge+disk decomposition, we conclude: (1) the morphologically decomposed bulges are composite structures comprised of a slowly rotating bulge, an inner halo, and a disky bulge; (2) kinematically disky bulges, akin to what are commonly called pseudo bulges in observations, are compact disk-like components that have rotation similar to warm disks; (3) halos contribute almost 30% of the surface density of the outer part of morphological disks when viewed face-on; and (4) both cold and warm disks are often truncated in central regions.

中文翻译：

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IllustrisTNG 盘状星系的运动学分解：形态学及其与形态结构的关系

我们最近开发了一种自动化方法 auto-GMM 来分解模拟星系。它以准确、高效和无监督的方式提取运动学结构。我们使用 auto-GMM 来研究来自 IllustrisTNG 的 TNG100 运行的盘状星系的恒星运动结构。我们确定了四到五个在不同星系群中普遍存在的结构。具有强到中度旋转的结构分别被定义为冷盘和暖盘。以随机运动为主的球体结构被归类为凸起或恒星晕，这取决于它们的结合程度。盘状凸起是具有适度旋转但形态紧凑的结构。在所有盘状星系中，考虑到 3 个半质量半径内的恒星质量，运动学球体结构，通过将凸起和光晕的恒星相加获得，占恒星总质量的约 45%，而盘状结构占 55%。这项研究还提供了关于运动学和形态学派生的星系结构之间关系的重要见解。将运动学结构的形态与传统的凸起+圆盘分解的形态进行比较，我们得出结论：（1）形态分解的凸起是由缓慢旋转的凸起、内晕和盘状凸起组成的复合结构；(2) 运动学上的圆盘状凸起，类似于观测中通常称为伪凸起的东西，是具有类似于暖盘旋转的致密盘状组件；(3) 当正面观察时，晕占形态盘外部表面密度的近 30%；