对NGC 5023和UGC 2082的HALOGAS观测：边缘星系中非圆柱对称气体分布的模拟
HALOGAS observations of NGC 5023 and UGC 2082: Modeling of non-cylindrically symmetric gas distributions in edge-on galaxies
摘要：
近年来，人们已经清楚地认识到，盘状星系的垂直结构是理解星系演化的一个关键因素。特别是，面外气体的存在和结构一直是研究的焦点。氢吸积在LOcal GALAXIES（HALOGAS）调查的目的是提供一个普查的速度冷中性气体吸积在附近的星系，以及一组统计上显着的星系，可以调查其额外的平面气体属性。为了更好地理解两个边对HALOGAS星系NGC 5023和UGC 2082中中性氢的垂直结构，我们构造了详细的倾斜环模型。添加类似弧形或旋臂的扭曲显着改善了模型对这些星系的拟合。在UGC 2082的情况下，无论是对称模式还是非对称模式，都不需要旋转速度的垂直梯度来匹配观测结果。最佳拟合模型的特点是两个弧大的垂直范围，可能是由于吸积。在NGC 5023的情况下，在对称模式中需要垂直梯度（dV/dz = $-14.9\pm3.8$ km s $^{-1}$ kpc $^{-1}$），当考虑非对称模式时，其幅度显著降低（dV/dz = $-9.4\pm3.8$ km s $^{-1}$ kpc $^{-1}$）。此外，它表明，NGC 5023的基础磁盘可以对称，在所有参数，除了翘曲，在非对称模型。与“经典”建模相比，这些模型在有限的自由参数的情况下更好地拟合数据。
英文摘要：
In recent years it has become clear that the vertical structure of disk galaxies is a key ingredient for understanding galaxy evolution. In particular, the presence and structure of extra-planar gas has been a focus of research. The Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey aims to provide a census on the rate of cold neutral gas accretion in nearby galaxies as well as a statistically significant set of galaxies that can be investigated for their extra-planar gas properties. In order to better understand the the vertical structure of the neutral hydrogen in the two edge-on HALOGAS galaxies NGC 5023 and UGC 2082 we construct detailed tilted ring models. The addition of distortions resembling arcs or spiral arms significantly improves the fit of the models to these galaxies. In the case of UGC 2082 no vertical gradient in rotational velocity is required in either symmetric models nor non-symmetric models to match the observations. The best fitting model features two arcs of large vertical extent that may be due to accretion. In the case of NGC 5023 a vertical gradient is required in symmetric models (dV/dz =$-14.9\pm3.8$ km s$^{-1}$ kpc$^{-1}$) and its magnitude is significantly lowered when non-symmetric models are considered (dV/dz =$-9.4\pm3.8$ km s$^{-1}$ kpc$^{-1}$). Additionally it is shown that the underlying disk of NGC 5023 can be made symmetric, in all parameters except the warp, in non-symmetric models. In comparison to the "classical" modeling these models fit the data significantly better with a limited addition of free parameters.
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