作为盘状星系合并历史示踪剂的年龄-厚度关系
The Age-Thickness Relation as a Tracer of the Merger History of Disk Galaxies
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中文总结 AI 辅助
研究盘状星系合并历史重建难题，利用TNG50模拟中银河系类似物，通过年龄-厚度关系（由$\Delta_z$量化）来追溯，该关系编码恒星相关信息，此诊断稳健且提供新途径，可助力重建星系合并历史与探测动力学演化。
中文摘要 AI 辅助
在星系形成的层级框架中，盘状星系由一系列合并和相互作用塑造，但从观测中重建这段历史仍具有挑战性。我们表明星系的合并历史在其恒星盘的垂直结构中留下了可测量的印记。利用TNG50模拟中的银河系类似物，我们证明由垂直恒星位置的色散（$\Delta_z$）量化的年龄-厚度关系，既编码了现有恒星的动力学加热，也编码了在扰动阶段形成的恒星的诞生条件。主要合并在年龄-$\Delta_z$关系中产生明显的阶梯状特征，而飞越相互作用产生较弱的局部增强。我们表明这种诊断在盘内不同位置是稳健的，对低于20%的分数距离不确定性基本不敏感，不过其时间分辨率受恒星年龄不确定性限制。由于年龄-$\Delta_z$关系仅依赖于恒星位置和年龄，它为传统运动学诊断提供了一个可观测的替代方案。随着当前和即将进行的以前所未有的精度绘制银河系的调查，这个框架为重建我们星系的合并历史和探测宇宙时间内盘状星系的动力学演化提供了一条新途径。
英文摘要
In the hierarchical framework of galaxy formation, disk galaxies are shaped by a sequence of mergers and interactions, yet reconstructing this history from observations remains challenging. We show that the merger history of a galaxy leaves measurable imprints in the vertical structure of its stellar disk. Using Milky Way analogues from the TNG50 simulations, we demonstrate that the Age-thickness relation, quantified by the dispersion of vertical stellar positions ($Δ_z$), encodes both the dynamical heating of pre-existing stars and the birth conditions of stars formed during perturbed phases. Major mergers produce pronounced, step-like features in the Age$-Δ_z$ relation, reflecting strong disk heating and subsequent re-formation of a thin disk, while flyby interactions generate weaker, localized enhancements associated primarily with disturbed star formation. We show that this diagnostic is robust across different locations within the disk and largely insensitive to fractional distance uncertainties lower than 20\%, though its temporal resolution is limited by uncertainties in stellar ages. Because the Age$-Δ_z$ relation relies only on stellar positions and ages, it provides an observationally accessible alternative to traditional kinematic diagnostics. With current and upcoming surveys mapping the Milky Way with unprecedented precision, this framework offers a new avenue for reconstructing the merger history of our Galaxy and probing the dynamical evolution of disk galaxies across cosmic time.
