发表机构
Ludong University; Bohai University; Qinghai Normal University; Academy of Plateau Science and Sustainability; Lanzhou University（鲁东大学; 渤海大学; 青海师范大学; 高原科学与可持续发展研究院; 兰州大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究在米尔格罗姆动力学框架下，通过三维流体动力学N体模拟探究超薄星系垂直结构演化，发现高MOND深度指数的星系模型更易维持超薄结构，验证了超薄盘可在该理论下长期保持垂直薄度。
AI 中文摘要
本研究在米尔格罗姆动力学（MOND）框架下探究超薄星系垂直结构的长期演化。通过构建受观测约束的UGC 7321模型，我们检验其星系盘能否在MOND引力场中维持极端扁平的结构；还构建了不同MOND深度指数$D_{\rm M}$的模型，探究全局MOND深度对星系盘演化的影响。我们使用Phantom of RAMSES代码开展三维流体动力学N体模拟，通过$(h_z/R_{\rm D})$、表征非轴对称结构与垂直屈曲的傅里叶振幅、垂直加热量及垂直回复力来量化星系盘的演化。在受观测约束的UGC 7321模型中，星系在模拟早期形成强棒并发生屈曲不稳定性，随后棒强度下降，最终呈现弱棒结构；恒星盘仅发生有限垂直增厚，50亿年后大部分仍处于超薄 regime，$h_z/R_{\rm D}<0.1$。对不同$D_{\rm M}$值模型的对比显示，本模型组中较低$D_{\rm M}$对应重子质量更高或星系盘更致密的模型，表现出更强的垂直加热和更显著的星系盘增厚；相反，较高$D_{\rm M}$对应质量更低或结构更弥散的模型，更倾向于维持超薄结构。总体而言，模拟结果表明，超薄星系盘在MOND下的长期孤立演化中可保持垂直薄度，且超薄结构的长期维持至少部分受星系处于低加速度 regime 的程度影响。
英文摘要
This work investigates the long-term evolution of the vertical structure of superthin galaxies within the framework of Milgromian dynamics (MOND). By constructing an observationally constrained model of UGC 7321, a typical superthin galaxy, we test whether its disc can maintain an extremely flattened structure in a MOND gravitational field. We also construct models with different values of the MOND depth index D_M to study how the global MOND depth affects disc evolution. We perform three-dimensional hydrodynamical N-body simulations using the publicly available code Phantom of RAMSES. In the observationally constrained model of UGC 7321, the galaxy develops a strong bar and undergoes a buckling instability during the early stages of the simulation. The bar strength then decreases gradually, and the system eventually exhibits a weak bar structure. The vertical evolution reflects the combined effects of heating induced by non-axisymmetric structures and vertical confinement in the Milgromian potential. The stellar disc undergoes only limited vertical thickening, and the disc remains largely within the superthin regime, h_z/R_D<0.1, after 5.0 Gyr. The comparison of models with different D_M values suggests that models with lower D_M values, associated in our model suite with higher baryonic masses or more compact discs, exhibit stronger vertical heating and more significant disc thickening. By contrast, models with higher D_M values, corresponding to lower masses or more diffuse structures, tend to maintain a superthin structure. Overall, the simulation results indicate that superthin discs can remain vertically thin during long-term isolated evolution in MOND, and that the long-term maintenance of superthin structures is influenced, at least partly, by the degree to which a galaxy lies in the low-acceleration regime.
Comments15 pages,14 figures,3 tables,accepted for publication in A&A
