AI 中文总结
本研究基于SAMI星系巡天，用DYNAMITE代码构建Schwarzschild轨道叠加模型，发现星系轨道占比与λ_Re、恒星年龄相关，证实合并驱动加热是大质量星系角动量再分布的主导机制。
AI 中文摘要
星系的角动量演化由内部长期过程与合并等外部机制共同塑造。基于轨道叠加的动力学建模为关联星系的内禀轨道结构与其全局属性和合并历史提供了有力手段。我们使用DYNAMITE代码构建了大质量（log(M/M☉)>10）SAMI星系的Schwarzschild轨道叠加模型，利用深度KiDS测光精确复现每个星系的光度分布。我们发现热轨道、冷轨道、温轨道及反向旋转轨道的占比均与自旋参数代理量λ_Re存在显著相关性，其中热轨道加反向旋转轨道的组合占比相关性最强。在控制恒星质量与环境的情况下，我们发现热轨道和冷轨道的占比与恒星年龄存在显著相关性，而温轨道则无此关联。我们还发现，具有壳层合并特征的年轻星系的λ_Re值低于全样本，这由热轨道过剩和冷轨道不足导致，与温轨道无关。我们认为，该SAMI样本中的运动学转变是恒星直接从冷轨道过渡到热轨道的过程，由于温轨道预期源于长期加热过程，这些发现表明合并驱动的加热是大质量星系角动量再分布及旋转支撑减弱的主导机制。
英文摘要
The evolution of angular momentum in galaxies is shaped by a combination of internal secular processes and external mechanisms such as mergers. Orbit-superposition based dynamical modelling provides a powerful means of linking the intrinsic orbital structures of galaxies to their global properties and merger histories. We construct Schwarzschild orbit-superposition models of massive ($\log(M/M_{\odot})>10$) SAMI galaxies using the DYNAMITE code, utilising deep KiDS photometry to accurately reproduce each galaxy's luminosity distribution. We find that the fractions of hot, cold, warm, and counter-rotating orbits all show significant correlations with the spin parameter proxy $λ_{R_e}$, with the strongest correlation arising from the combined hot plus counter-rotating fraction. When controlling for stellar mass and environment, we find that the fraction of hot and cold orbits show significant correlations with stellar age, whereas warm orbits do not. We further find that the lower values of $λ_{R_e}$ for young galaxies with shell merger features as compared to the full sample is driven by an excess of hot orbits and a deficit of cold orbits, with no dependence on warm orbits. We suggest that the kinematic transformation in this SAMI sample proceeds through stars transitioning directly from cold to hot orbits. As warm orbits are expected to arise from secular heating processes, these findings indicate that merger-driven heating is the dominant mechanism governing the redistribution of angular momentum and the reduction of rotational support in massive galaxies.
Comments32 pages, 25 figures, accepted to Monthly Notices of the Royal Astronomical Society (MNRAS)
