论文标题
外场对磁盘星系中径向加速的效应的数值解
Numerical Solutions of the External Field Effect on the Radial Acceleration in Disk Galaxies
论文作者
论文摘要
在基于牛顿动力学的理论（修改后的牛顿动力学）中，强度对等原理通常以特殊的方式破坏，这体现在“外部田地效应（EFE）”的作用中。即使是恒定的外部字段，自我磨削系统中的内部动力也会受到影响。在磁盘星系中，EFE可以诱导翘曲并修改旋转速度。由于MOND的非线性，很难在磁盘中得出这种重要效果的分析表达。在这里，我们在两种非忠实的拉格朗日理论中以数字研究：“ aquadratic-lagrangian”理论（Aqual）和“ quasilinear mond”（Qumond）。对于Aqual，我们仅考虑沿磁盘轴的外部磁场的轴对称场配置，或带有倾向于外场的测试粒子轨道的球形星系。对于更易于管理的Qumond，我们还计算了三维字段配置，外部字段倾向于磁盘轴。我们特别研究外场在多大程度上修饰了旋转曲线的准灯平局部分。尽管我们的Qumond结果与Qumond已发表的数值结果非常吻合，但我们发现Aqual预测EFE弱于已发表的Aqual结果。但是，Aqual仍然预测比Qumond更强的EFE，这表明当前的理论不确定性。我们还说明了内部部分旋转曲线上升部分的MOND预测在很大程度上取决于磁盘厚度，但仅对固定星系模型的合理外部磁场进行了薄弱。最后，我们将外部部分的结果概括为改进的近似分析表达。
In MOND (modified Newtonian dynamics)-based theories the strong equivalence principle is generically broken in an idiosyncratic manner, manifested in the action of an "external field effect (EFE)". The internal dynamics in a self-gravitating system is affected even by a constant external field. In disk galaxies the EFE can induce warps and modify the rotational speeds. Due to the non-linearity of MOND, it is difficult to derive analytic expressions of this important effect in a disk. Here we study numerically the EFE in two non-relativistic Lagrangian theories of MOND: the `Aquadratic-Lagrangian' theory (AQUAL) and `Quasilinear MOND' (QUMOND). For AQUAL we consider only the axisymmetric field configurations with the external field along the disk axis, or a spherical galaxy with test-particle orbits inclined to the external field. For the more manageable QUMOND we calculate also the three-dimensional field configurations, with the external field inclined to the disk axis. We investigate particularly to what degree an external field modifies the quasi-flat part of rotation curves. While our QUMOND results agree well with published numerical results in QUMOND, we find that AQUAL predicts weaker EFE than published AQUAL results. However, AQUAL still predicts stronger EFE than QUMOND, which demonstrates current theoretical uncertainties. We also illustrate how the MOND prediction on the rising part of the rotation curve, in the inner parts, depends largely on disk thickness but only weakly on a plausible external field for a fixed galaxy model. Finally, we summarize our results for the outer parts as an improved, approximate analytic expression.
