MOND中M33的全局稳定性
The global stability of M33 in MOND
摘要：
盘状星系的动力学稳定性对它们的异常自转曲线是由暗物质晕还是Milgromian动力学（MOND）引起的很敏感。我们通过建立M33的MOND模型来研究这一点。我们首先模拟它在隔离6陀螺仪，从一个初始的良好匹配的旋转曲线（RC）。当气体过热时，会形成过大的条和凸起，但这可以通过降低气体温度来避免。在1 Gyr中仍然形成一个强的棒，但迅速减弱，并与观察到的弱棒一致。以前的工作表明，这是具有挑战性的牛顿模型与活的暗物质晕，其中发展出强大的酒吧。条形图速度意味着实际的共转半径为3 kpc。然而，RC仍然上升得太陡，中心视线速度色散（LOSVD）太高。然后，我们添加一个恒定的外部加速度场的$8.4 \times 10^{-12}$ m/s $^2$在$30^\circ$的磁盘作为一个一阶估计的重力M31施加。这抑制了材料在中心的积聚，导致RC上升得更慢，并降低了中心LOSVD。总的来说，这个模拟与M33的几个全局性质有很好的相似之处，并强调了即使是弱外场对盘状星系稳定性和演化的重要性。需要进一步模拟时变外部场，模拟M33的完整轨道，以确认其与观测的相似性。
英文摘要：
The dynamical stability of disk galaxies is sensitive to whether their anomalous rotation curves are caused by dark matter halos or Milgromian Dynamics (MOND). We investigate this by setting up a MOND model of M33. We first simulate it in isolation for 6 Gyr, starting from an initial good match to the rotation curve (RC). Too large a bar and bulge form when the gas is too hot, but this is avoided by reducing the gas temperature. A strong bar still forms in 1 Gyr, but rapidly weakens and becomes consistent with the observed weak bar. Previous work showed this to be challenging in Newtonian models with a live dark matter halo, which developed strong bars. The bar pattern speed implies a realistic corotation radius of 3 kpc. However, the RC still rises too steeply, and the central line of sight velocity dispersion (LOSVD) is too high. We then add a constant external acceleration field of $8.4 \times 10^{-12}$ m/s$^2$ at $30^\circ$ to the disk as a first order estimate for the gravity exerted by M31. This suppresses buildup of material at the centre, causing the RC to rise more slowly and reducing the central LOSVD. Overall, this simulation bears good resemblance to several global properties of M33, and highlights the importance of including even a weak external field on the stability and evolution of disk galaxies. Further simulations with a time-varying external field, modeling the full orbit of M33, will be needed to confirm its resemblance to observations.
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