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arXiv 2602.06182astro-ph.GA
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银河盘中的径向速度波

On the radial velocity wave in the Galactic disk

Institute for Advanced Study(高等研究院);Department of Astrophysical Sciences, Princeton University(普林斯顿大学天体物理科学系)

Chris Hamilton, Andrew Mummery, Joss Bland-Hawthorn

AI总结:

本文通过线性扰动理论推导出解释银河盘中径向速度波的解析公式,并通过模拟验证其准确性,发现短寿命螺旋臂扰动能产生符合数据的信号。

摘要:

银河盘中的恒星具有随角动量J_φ变化的平均径向速度v_R的均值,这种J_φ-v_R波信号在按动态温度分组时也表现出系统性的相位偏移。然而,该波的起源尚不清楚。本文利用线性扰动理论推导出一个简单的解析公式,该公式依赖于银河系的平衡性质和近期扰动的历史。该公式自然解释了相位偏移,但也预测不同类别的扰动应驱动J_φ-v_R信号具有非常不同的形态。忽略盘波动的自引力,它表明远距离潮汐踢(例如,来自Sgr矮星系)或刚性旋转的银河系棒都无法产生符合要求的J_φ-v_R波信号。然而,短寿命的螺旋臂可以做到这一点,并通过MCMC拟合识别出一个驱动J_φ-v_R信号的螺旋扰动,该信号与数据合理一致。我们通过测试粒子模拟验证了解析公式,发现其在应用于动态冷恒星群体时非常准确。需要进一步工作以处理更热的轨道,并纳入波动的自引力和星际气体的作用。

英文摘要:

Stars in the Galactic disk have mean radial velocities $\overline{v}_R$ that oscillate as a function of angular momentum $J_φ$. This `$J_φ$-${\overline{v}}_R$ wave' signal also exhibits a systematic phase shift when stars are binned by their dynamical temperatures. However, the origin of the wave is unknown. Here we use linear perturbation theory to derive a simple analytic formula for the $J_φ$-$\overline{v}_R$ signal that depends on the equilibrium properties of the Galaxy and the history of recent perturbations to it. The formula naturally explains the phase shift, but also predicts that different classes of perturbation should drive $J_φ$-$\overline{v}_R$ signals with very different morphologies. Ignoring the self-gravity of disk fluctuations, it suggests that neither a distant tidal kick (e.g., from the Sgr dwarf) nor a rigidly-rotating Galactic bar can produce a qualitatively correct $J_φ$-$\overline{v}_R$ wave signal. However, short-lived spiral arms can, and by performing an MCMC fit we identify a spiral perturbation that drives a $J_φ$-${\overline{v}}_R$ signal in reasonable agreement with the data. We verify the analytic formula with test particle simulations, finding it to be highly accurate when applied to dynamically cold stellar populations. More work is needed to deal with hotter orbits, and to incorporate the fluctuations' self-gravity and the role of interstellar gas.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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