论文标题
轴对称stäckel电位中恒星流中差距的时间演变
Time evolution of gaps in stellar streams in axisymmetric Stäckel potentials
论文作者
论文摘要
当Subhalo与冷恒星流相互作用时，它会使其恒星的平滑分布散布，这导致了间隙的产生。这种间隙的属性取决于相互作用的参数。因此，它们的特征可能导致确定遗物的质谱，并可能揭示出绕着银河系的黑暗subhalos的存在。我们的目标是构建一个完全分析的模型，以嵌入在循环的银河系潜力的流中嵌入的差距的形成和演变。为此，我们将Helmi＆Koppelman（2016）的模型扩展到球形电位上，并预测轴对称性Stäckel电位中流中的间隙的特性。我们利用动作角度及其简单的行为来计算最初因与次荷兰的相互作用而略微扰动的附近轨道的差异。通过N体实验证实的我们的模型预测，间隙的大小随时间线性增长。我们获得了生长速率对流轨道的依赖性的分析表达式，subhalo的特性（质量，拉迪乌斯）和相遇的几何形状（相对速度，影响参数）。我们发现，间隙中心的密度随时间而降低，就像流的密度相同。这导致原始轨道上的原始流和扰动流之间的密度对比，从而仅取决于相遇参数，从而达到恒定值。我们发现，在固定的年龄，小间隙主要对subhalo的质量敏感，而subhalo flybys形成的间隙较低，相对速度较低，或者在平行流和亚豪元移动时，差异为遇到参数。
When a subhalo interacts with a cold stellar stream it perturbs its otherwise nearly smooth distribution of stars, and this leads to the creation of a gap. The properties of such gaps depend on the parameters of the interaction. Their characterisation could thus lead to the determination of the mass spectrum of the perturbers and possibly reveal the existence of dark subhalos orbiting the Milky Way. Our goal is to construct a fully analytical model of the formation and evolution of gaps embedded in streams orbiting in a realistic Milky Way potential. To this end, we extend the model of Helmi & Koppelman (2016) for spherical potentials, and predict the properties of gaps in streams evolving in axisymmetric Stäckel potentials. We make use of action-angles and their simple behaviour to calculate the divergence of initially nearby orbits slightly perturbed by the interaction with a subhalo. Our model, corroborated by N-body experiments, predicts that the size of a gap grows linearly with time. We obtain analytical expressions for the dependencies of the growth rate on the orbit of the stream, the properties of the subhalo (mass, scale-radius), and the geometry of the encounter (relative velocity, impact parameter). We find that the density at the centre of the gap decreases with time as a power-law in the same way as the density of a stream. This results in the density-contrast between a pristine and a perturbed stream on the same orbit asymptotically reaching a constant value dependent only on the encounter parameters. We find that at a fixed age, smallish gaps are sensitive mostly to the mass of the subhalo, while gaps formed by subhalo flybys with a low relative velocity, or when the stream and subhalo move parallel, are degenerate to the encounter parameters.
