arXiv 0804.02172008-04-01astro-ph

不同薄盘引力模型对银河系自转的描述

Galactic Rotation Described with Various Thin-Disk Gravitational Models

James Q. Feng, C. F. Gallo

备注：: 13 Pages + 8 Figures

摘要：

对于成熟的旋涡星系，自转速度从星系中心开始迅速增加，从核心到外围达到恒定速度。这种动态行为所描述的模型平衡牛顿的重力和离心力旋转薄轴对称磁盘。弗里曼的圆盘假设质量密度随半径呈指数下降，这正确地产生了从银河系中心到外核附近的最大值增加的旋转速度，但随后与测量相反，向外围减小。梅斯泰尔的圆盘假设质量分布下降得更慢（与半径成反比），在整个圆盘上产生恒定的旋转速度，但有一个不切实际的中心质量奇点，并且没有正确描述核心旋转。因此，结合弗里曼和梅斯特磁盘，利用他们的长处，消除他们的不足。利用弗里曼公式的中央核心，和梅斯特尔公式超出核心的银河系边缘。这个组合模型产生的旋转曲线可以与成熟旋涡星系的测量结果相媲美。对于一个更一般的薄盘模型，我们开发了一种替代的计算方法来解决各种测量的旋转曲线的质量密度分布，我们计算径向质量密度，平衡牛顿引力和离心力在每一点上。计算的解决方案表明，质量密度下降近似指数在中央核心（类似弗里曼），并过渡到一个较慢的反向径向减少（类似梅斯特）的周边。因此，这些不同的方法产生类似的结果，并相互自洽与牛顿引力/动力学。

英文摘要：

For mature spiral galaxies, the rotation velocities quickly increase from the galactic center and achieve a constant velocity from the core to the periphery. This dynamic behavior is described by models balancing Newtonian gravitational and centrifugal forces in rotating thin axisymmetric disks. Freeman's disk assumes a mass density decreasing exponentially with radius which correctly produces rotational velocities which increase from the galactic center to a maximum near the outer core, but then decreases out to the periphery contrary to measurements. Mestel's disk assumes a mass distribution decreasing more slowly (inversely with radius) that yields a constant rotational velocity across the entire disk, but has an unrealistic central mass singularity and does not describe the core rotation properly. Thus combine the Freeman and Mestel disks to utilize their strengths and eliminate their deficiencies. Utilize the Freeman formula for the central core, and the Mestel formula beyond the core to the galactic rim. This combined model produces rotation curves comparable to the measurements of mature spiral galaxies. For a more general thin-disk model, we develop an alternative computational method to solve for the mass density distributions for various measured rotation curves We compute radial mass densities that balance the Newtonian gravitational and centrifugal forces at every point. The computational solutions show mass densities which decrease approximately exponentially in the central core (similar to Freeman), and transition to a slower inverse radial decrease (similar to Mestel) to the periphery. Thus these diverse approaches yield similar results and are mutaully self-consistent with Newtonian gravity/dynamics.

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