在相空间中编码的潮汐诱导的螺旋臂缠绕
Tidally induced spiral arm wraps encoded in phase space
摘要：
我们研究潮汐引起的螺旋臂在我们的银河系的背景下，它遇到人马座的动力学。我们建立了一个主机和卫星星系之间的相互作用的玩具模型，使用轨道积分后，潮汐遇到。我们推导出解析的形状的结构在相空间中作为时间的函数简单的幂律势模型。我们将这些模型与MW人马座相互作用的更现实的N体模拟和来自盖亚DR 3的数据进行了比较。如前所述，一个星系卫星的脉冲遥远潮汐方法导致了一个双臂螺旋结构，由它们的远心点和近心点之间的轨道组成，因此，具有平均负的银河系径向速度。双臂图案以取决于半径的角速度$ω-1/2κ$旋转，从而导致随时间的卷起。这在$R$ - $V_ϕ$投影中产生脊，在$L_Z$ - $ϕ$空间中交替出现$V_R$符号和$V_R$振荡，就像在盖亚数据中观察到的那样。这些运动学特征的频率随时间增加，提供了一个强大的手段来推断潜在的和扰动的开始时间和方位角相位。傅立叶分析使我们能够日期的影响时间的简单模型，甚至日期的扰动，从各种近心通道。对于MW，傅立叶分析表明两个不同频率的叠加，如在以前的研究。假设两者都是由于脉冲和遥远的近心点通道，我们发现扰动时间<0.6 Gyr，范围为0.8-2.1 Gyr。后者与人马座先前的近心点相一致，并与观测到的径向范围内的旋臂的四圈有关。有必要进一步研究星系盘的自引力响应和可能的酒吧与长期过程的简并。（澳大利亚广播公司）
英文摘要：
We study the dynamics of tidally induced spiral arms in our Galaxy in the context of its encounters with Sagittarius. We built toy models of the interaction between a host and a satellite galaxy using orbital integrations after a tidal encounter. We derived analytically the shape of the structures in phase space as a function of time for simple power-law potential models. We compared these models to a more realistic N-body simulation of the MW Sagittarius-like interaction and to data from Gaia DR3. As found before, an impulsive distant tidal approach of a galactic satellite leads to a two-armed spiral structure made of orbits in between their apocentres and pericentres, thus, with average negative galactocentric radial velocity. The two-arm pattern rotates at an angular speed of $ω-1/2κ$ which depends on radius, thus causing a wind-up with time. This produces ridges in the $R$-$V_ϕ$ projection with alternating signs of $V_R$ and oscillations of $V_R$ in the $L_Z$-$ϕ$ space, like those observed in the Gaia data. The frequency of these kinematic features increases with time, offering a powerful means to infer the potential and the perturbation's onset time and azimuthal phase. Fourier analysis allows us to date the impact times of simple models and even to date perturbations from various pericentric passages. For the MW, the Fourier analysis indicates a superposition of two different frequencies, as in previous studies. Assuming that both are due to impulsive and distant pericentre passages, we find perturbation times <0.6 Gyr and in the range of 0.8-2.1 Gyr. The latter is compatible with a previous pericentre of Sagittarius and would be related to four wraps of the spiral arms in the observed radial range. Further work on the self-gravitating response of galactic discs and possible degeneracies with secular processes by the bar is necessary. (ABR)
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