IllustrisTNG模拟中并合如何塑造星系形态
How mergers shape galaxy morphology in the IllustrisTNG simulation
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中文总结 AI 辅助
本研究通过IllustrisTNG模拟，发现并合后星系形态由碰撞角、冷气体占比及并合前形态决定，揭示了并合塑造星系形态的复杂机制。
中文摘要 AI 辅助
星系并合如何驱动形态演化仍是一个开放问题。传统观点认为，主并合产生椭圆星系，而并合则形成如星系核球这类弥散主导的成分；但近期研究对这一简单图景提出挑战，表明演化场景更为复杂。本研究使用IllustrisTNG宇宙学模拟，在广泛的星系质量和并合质量比范围内，探究并合如何塑造星系形态。结果显示，并合后星系形态主要由三个因素决定：碰撞角$\boldsymbol{\theta}$、冷气体占比$f_{\text{cold gas}}$，以及并合前星系形态$\boldsymbol{(B/T)_{*,pre}}$。具体而言，具有大$\boldsymbol{\theta}$的螺旋式并合会增加系统的旋转支撑，使气体沉降为延展盘；当系统富含冷气体时，新形成气体盘内的恒星形成会进一步增强遗迹的盘主导结构。另一方面，具有小$\boldsymbol{\theta}$的对撞式并合通常会破坏有序星系运动，产生更多弥散支撑的遗迹。总体而言，我们在并合驱动星系形态转变的统一图景下解读这些结果。
英文摘要
How galaxy mergers drive morphological evolution remains an open question. Traditional views hold that major mergers produce elliptical galaxies, while minor mergers form dispersion-dominated components such as galactic bulges. However, more recent work has challenged this simple picture, suggesting a more complex evolutionary scenario. In this study, we use the IllustrisTNG cosmological simulation to investigate how mergers shape galaxy morphology, across a broad range of galaxy masses and merger mass ratios. Our results show that the post-merger galaxy morphology is primarily determined by three factors: collision angle $\overlineθ$, cold gas fraction $f_\mathrm{cold\,gas}$, and pre-merger galaxy morphology $\mathrm{(B/T)_{*,pre}}$. Specifically, spiral-in mergers with large $\overlineθ$ increase the rotational support of the system, allowing the gas to settle into an extended disk. When the system is rich in cold gas, star formation within the newly formed gas disk can further strengthen the disk-dominated structure of the remnant. On the other hand, head-on mergers with small $\overlineθ$ typically disrupt ordered galactic motion, producing more dispersion-supported remnants. Overall, we interpret our results within a unified picture of merger-driven morphological transformation in galaxies.
