银河地震学：盘内冲击能否解释银河系盘的大尺度扰动？
Galactic seismology: can a disc-crossing impulse explain the large-scale perturbations in the Milky Way's disc?
AI总结：
研究通过模拟Sgr矮星系单次穿越冲击，探讨其是否能解释银河系盘的大尺度扰动，发现其能合理重现部分特征，但无法完全解释L_z-VR波，需考虑其他触发因素。
摘要：
在坠入之前，银心矮星系（Sgr）是一个质量约为10^11 M_sun的主流卫星。在过去的5-6十亿年里，它已被银河系（MW）严重剥离，穿越银河系盘多次时失去了大部分质量。最近对银河系盘扰动的模型，包括旋臂、恒星棒、Gaia相位旋臂、恒星和气体盘的波浪形起伏，已经将这些穿越视为可能的形成触发因素，但通常将每个扰动孤立处理。在这里，我们采用整体视角，询问一次盘内冲击是否能同时解释这些今天观测到的特征。我们专注于由类似Sgr的扰动体引起的单次盘内冲击的模拟，并对强大冲击在形成旋臂、盘波浪形起伏、相位旋臂以及由恒星角动量和径向速度确定的L_z-VR波的作用进行了细致分析。我们发现，一次盘内冲击可以合理地重现（例如结构、振幅、相位）观测到的局部盘波浪形起伏，以及外臂、本地臂和银心-船底座臂段，这意味着最后一次显著冲击由于穿越发生在约700-1200万年前。此外，L_z-VR波和相位旋臂在模拟中在同一时期出现，其总体结构可以合理地复制，但不细致。我们得出结论，Sgr最后一次显著穿越大约一亿年前可能是银河系盘大尺度扰动的主要原因，但无法完全解释L_z-VR波。因此，其他触发因素，可能是银河系棒或与其他卫星的相互作用，必须被考虑，以充分解释当前银河系盘的动力学状态。
英文摘要：
Prior to its infall, the Sagittarius (Sgr) dwarf galaxy was a major satellite with a mass of $M_{\rm sgr}\sim 10^{11}$ M$_\odot$. For the past $5-6~\mathrm{Gyr}$ , it has been heavily stripped by the Milky Way (MW), losing most of its mass while crossing the MW disc multiple times. Recent models of Milky Way disc perturbations $-$ including the spiral arms, the stellar bar, the Gaia phase spiral, and stellar and gaseous disc corrugations $-$ have identified these crossings as possible formation triggers, but have generally treated each perturbation in isolation. Here, we adopt a holistic perspective and ask whether a single disc-crossing impulse can simultaneously account for these features as observed today. We focus on simulations of single disc-crossing events by a Sgr-like perturber, and present a forensic analysis of the role of the powerful impulse in forming spiral arms, disc corrugations, the phase spiral and the `$L_{z}-\bar{V}_{R}$ wave', determined from a star's angular momentum and radial velocity, respectively. We find that a single disc crossing can reproduce reasonably well (e.g. structure, amplitude, phase) the observed local disc corrugation, and the Outer, Local and Sagittarius-Carina arm segments, implying that the last significant impulse due to a transit took place $700-1200~\mathrm{Myr}$ ago. Moreover, the $L_{z}-\bar{V}_{R}$ wave and phase spiral appear within the simulations over the same epoch and their general structure is reasonably well replicated, but not in detail. We conclude that Sgr's last significant crossing roughly a Gyr ago could be the primary cause of large-scale MW disc perturbations, but it cannot fully account for the $L_{z}-\bar{V}_{R}$ wave. Consequently, other triggers, possibly the Galactic bar or interactions with other satellites, must be considered in order to fully explain the current dynamical state of the MW's disc.
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