Title: Limitations and rotation of the two-armed phase spiral in the Milky Way stellar disc Show Chinese title

Title: 银河系恒星盘中双臂螺旋的局限性和旋转

Abstract: Context: The Milky Way's history of recent disturbances is vividly demonstrated by a structure in the vertical phase-space distribution known as the Gaia phase spiral. A one-armed phase spiral has been seen widely across the Milky Way disc, while a two-armed one has only been observed in the solar neighbourhood. Aims: This study aims to determine the properties of the two-armed phase spiral and to put it in a Galactic context, with the ultimate goal of understanding the structure and history of the Milky Way disc. Methods: The Gaia DR3 data is used to trace and characterise the two-armed phase spiral. Special focus is put on the phase spiral's spatial distribution, rotational behaviour, and chemical characteristics. To quantify the properties of the phase spiral we use a model that fits a spiral pattern to the phase space distribution of the stars. Results: We find that the two-armed phase spiral is detectable only within a narrow range of galactocentric distances and angular momenta in the solar neighbourhood, $R = 8 \pm 0.5 $ kpc, $L_Z = 1450 \pm 50$ kpc km s$^{-1}$. Outside this region, the phase spiral is one-armed. The two-armed phase spiral rotates with the phase angle, like the one-armed phase spiral, and changes axis ratio with phase angle. Additionally, stars within the phase-space overdensity caused by the two-armed phase spiral pattern have slightly higher mean metallicity than stars in the underdense regions of the pattern at equivalent galactocentric distances, angular momenta, and vertical orbit extents. Conclusions: The two-armed phase spiral rotates with phase angle and its effect can be seen in metallicity, like the one-armed phase spiral. However, the limited range over which it can be found, and its variation in shape are quite different from the one-armed version, suggesting it is a much more localised phenomenon in the Galactic disc. Show Chinese abstract

Abstract: 上下文：银河系近期扰动的历史通过垂直相空间分布中称为盖亚相位螺旋的结构得到了生动的展示。 一个单臂相位螺旋在银河系盘中广泛存在，而一个双臂相位螺旋仅在太阳邻域被观测到。 目标：本研究旨在确定双臂相位螺旋的特性，并将其置于银河系背景下，最终目标是理解银河系盘的结构和历史。 方法：使用盖亚DR3数据来追踪和表征双臂相位螺旋。特别关注相位螺旋的空间分布、旋转行为和化学特征。为了量化相位螺旋的特性，我们使用了一个将螺旋模式拟合到恒星相空间分布的模型。 结果：我们发现双臂相位螺旋仅在太阳邻域的狭窄范围内的银河中心距离和角动量范围内可被检测到，$R = 8 \pm 0.5 $kpc，$L_Z = 1450 \pm 50$kpc km s$^{-1}$。在此区域之外，相位螺旋是单臂的。双臂相位螺旋像单臂相位螺旋一样以相位角旋转，并且随着相位角改变轴比。此外，在由双臂相位螺旋模式引起的相空间高密度区内的恒星，在等效的银河中心距离、角动量和垂直轨道范围下，其平均金属含量略高于模式低密度区的恒星。 结论：双臂相位螺旋以相位角旋转，其影响在金属含量中可见，就像单臂相位螺旋一样。然而，它只能在有限的范围内找到，且形状变化较大，与单臂版本有很大不同，这表明它是银河系盘中一个更加局部的现象。