Stability of Disk Galaxies in the Modified Dynamics
Stability of Disk Galaxies in the Modified Dynamics
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DOI：
10.1086/307402
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发表时间：
1998-11
期刊：
影响因子：
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通讯作者：
R. Brada;M. Milgrom
中科院分区：
文献类型：
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作者：
R. Brada;M. Milgrom
一般的分析论证使我们期望在修正的牛顿动力学（MOND）中，自引力盘比牛顿动力学中的同类更稳定。我们研究这个问题的数值，使用粒子网格代码的基础上的（非线性）MOND场方程的多重网格求解器。我们开始与平衡分布函数的MOND磁盘模型具有平滑截断，指数表面密度分布和一个常数Toomre Q参数。我们发现，事实上，磁盘的一个给定的“温度”是当地更稳定的MOND比牛顿动力学。至于全球不稳定酒吧的形成，我们发现，作为在磁盘的平均加速度降低磁盘的稳定性增加，因为我们从牛顿到MOND政权交叉。稳定性的程度在MOND体系中逐渐稳定，正如MOND中的标度律所预期的那样。对于我们使用的盘模型，这种最大程度的稳定性类似于在5个盘尺度长度下由3倍质量的晕赋予牛顿盘的稳定性。
General analytic arguments lead us to expect that in the modified Newtonian dynamics (MOND), self-gravitating disks are more stable than their like in Newtonian dynamics. We study this question numerically, using a particle-mesh code based on a multigrid solver for the (nonlinear) MOND field equation. We start with equilibrium distribution functions for MOND disk models having a smoothly truncated, exponential surface density profile and a constant Toomre Q-parameter. We find that, indeed, disks of a given "temperature" are locally more stable in MOND than in Newtonian dynamics. As regards global instability to bar formation, we find that as the mean acceleration in the disk is lowered the stability of the disk is increased as we cross from the Newtonian to the MOND regime. The degree of stability levels off deep in the MOND regime, as expected from scaling laws in MOND. For the disk model we use, this maximum degree of stability is similar to the one imparted to a Newtonian disk by a halo 3 times as massive at 5 disk scale lengths.