An ever-present Gaia snail shell triggered by a dark matter wake
An ever-present Gaia snail shell triggered by a dark matter wake
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DOI：
10.1093/mnras/stad1969
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发表时间：
2022-11
影响因子：
4.8
通讯作者：
R. Grand;R. Pakmor;F. Fragkoudi;Facundo A. G'omez;Wilma H. Trick;C. Simpson;F. van de Voort;R. Bieri
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文献类型：
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作者：
R. Grand;R. Pakmor;F. Fragkoudi;Facundo A. G'omez;Wilma H. Trick;C. Simpson;F. van de Voort;R. Bieri
我们利用一种新颖的数值技术来模拟星系形成的宇宙学模拟中的恒星形成（称为超级恒星），以模拟具有 ≳108 个恒星粒子的类银河系，以研究在完整的宇宙学环境中不平衡恒星盘结构的形成和演化。在由垂直于中面[垂直相空间，(Z，VZ)]的坐标和速度定义的平面中，类太阳体积中的恒星在晚期表现出在形状和振幅上与盖亚“蜗牛壳”相螺旋性质相似的清晰螺旋。我们证明，在极轨道上的 ∼1010$\rm {\rm M}_{\odot }$ 卫星经过近心点期间，相位螺旋在 ∼6 Gyr 的回顾时间形成。这颗卫星刺激暗物质晕中共振尾流的形成，同时以每轨道环约 0.5-1 dex 的速度损失质量。太阳半径处尾流引起的引力扭矩的峰值约为卫星引力扭矩的 8 倍，并触发盘扭曲的形成，随着时间的推移，盘扭曲会卷绕成垂直相位螺旋。随着尾流的衰减，相位螺旋传播了数千兆年至今，一旦稳定的盘演化建立起来，就可以被描述为“永远存在”。这些结果提出了解释盖亚相位螺旋的另一种情况，该情况不依赖于杆屈曲的扰动或最近来自卫星的直接撞击。
We utilize a novel numerical technique to model star formation in cosmological simulations of galaxy formation – called superstars – to simulate a Milky Way-like galaxy with ≳108 star particles to study the formation and evolution of out-of-equilibrium stellar disc structures in a full cosmological setting. In the plane defined by the coordinate and velocity perpendicular to the mid-plane [vertical phase space, (Z, VZ)], stars in solar-like volumes at late times exhibit clear spirals qualitatively similar in shape and amplitude to the Gaia ‘snail shell’ phase spiral. We show that the phase spiral forms at a lookback time of ∼6 Gyr during the pericentric passage of an ∼1010$\rm {\rm M}_{\odot }$ satellite on a polar orbit. This satellite stimulates the formation of a resonant wake in the dark matter halo while losing mass at a rate of ∼0.5–1 dex per orbit loop. The peak magnitude of the wake-induced gravitational torque at the solar radius is ∼8 times that from the satellite, and triggers the formation of a disc warp that wraps up into a vertical phase spiral over time. As the wake decays, the phase spiral propagates several gigayears to present day and can be described as ‘ever-present’ once stable disc evolution is established. These results suggest an alternative scenario to explain the Gaia phase spiral, which does not rely on a perturbation from bar buckling or a recent direct hit from a satellite.