超薄星系UGC 7321中所有半径处的暗物质优势
Dark matter dominance at all radii in the superthin galaxy UGC 7321
摘要：
利用观测到的旋转曲线和HI标度高度数据同时作为约束条件，模拟了低表面亮度超薄星系UGC 7321的暗物质晕的形状和密度分布。我们把星系看作是一个由恒星和气体组成的引力耦合系统，对暗物质晕的引力势作出反应。一个球形的等温晕，其核心密度在0.039 ~ 0.057 M_sun/pc ^3之间，核心半径在2.5 ~ 2.9 kpc之间，在假设的实际气体参数范围内，与观测结果最吻合。我们发现，最佳拟合的核心半径仅略高于恒星盘尺度长度（2.1 kpc），不像高表面亮度星系的晕核心半径通常是恒星盘尺度长度的3-4倍。因此，我们的模型表明，暗物质晕主导着低表面亮度，超薄星系UGC 7321在所有半径的动态，包括星系的内部。
英文摘要：
We model the shape and density profile of the dark matter halo of the low surface brightness, superthin galaxy UGC 7321, using the observed rotation curve and the HI scale height data as simultaneous constraints. We treat the galaxy as a gravitationally coupled system of stars and gas, responding to the gravitational potential of the dark matter halo. An isothermal halo of spherical shape with a core density in the range of 0.039 - 0.057 M_sun/pc^3 and a core radius between 2.5 - 2.9 kpc, gives the best fit to the observations for a range of realistic gas parameters assumed. We find that the best-fit core radius is only slightly higher than the stellar disc scale length (2.1 kpc), unlike the case of the high surface brightness galaxies where the halo core radius is typically 3-4 times the disc scale length of the stars. Thus our model shows that the dark matter halo dominates the dynamics of the low surface brightness, superthin galaxy UGC 7321 at all radii, including the inner parts of the galaxy.
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