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arXiv 2407.04286astro-ph.GA
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银河系恒星盘中双臂相螺旋的局限性与旋转

Limitations and rotation of the two-armed phase spiral in the Milky Way stellar disc

Simon Alinder, Paul McMillan, Thomas Bensby

备注：
Submitted to A&A
发表信息：
A&A 690, A15 (2024)
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AI总结：

本文利用 Gaia DR3 数据研究银河系双臂相螺旋，发现其仅存在于太阳邻域狭窄的银心距和角动量范围内，随相位角旋转并影响恒星金属丰度，表明它是比单臂相螺旋更局域化的盘结构现象。

摘要：

背景：银河系近期扰动历史由一个被称为 Gaia 相螺旋的垂直相空间分布结构生动地展示出来。单臂相螺旋已在银河系盘中广泛观测到，而双臂相螺旋仅在太阳邻域被观测到。目的：本研究旨在确定双臂相螺旋的性质，并将其置于银河系大背景下，最终目标是理解银河系盘的结构和历史。方法：利用 Gaia DR3 数据追踪和刻画双臂相螺旋。特别关注相螺旋的空间分布、旋转行为和化学特征。为量化相螺旋的性质，我们使用一个将螺旋图样拟合到恒星相空间分布的模型。结果：我们发现双臂相螺旋仅在太阳邻域内一个狭窄的银心距和角动量范围内可探测到，即 $R = 8 \pm 0.5$ kpc，$L_Z = 1450 \pm 50$ kpc km s$^{-1}$。在该区域之外，相螺旋为单臂。双臂相螺旋随相位角旋转，与单臂相螺旋类似，并且其轴比随相位角变化。此外，在双臂相螺旋图样造成的相空间过密度区域内的恒星，在相同银心距、角动量和垂直轨道幅度下，其平均金属丰度略高于图样中低密度区域的恒星。结论：双臂相螺旋随相位角旋转，其效应可在金属丰度中看到，与单臂相螺旋类似。然而，其可被发现的有限范围以及形状的变化与单臂版本相当不同，表明它是银河系盘中一个更为局域化的现象。

英文摘要：

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.

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