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arXiv 1108.0660astro-ph.GA
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用歧管模拟Milky Way的内部盘。我-第一步

Modelling the inner disc of the Milky Way with manifolds. I - A first step

M. Romero-Gomez, E. Athanassoula, T. Antoja, F. Figueras

备注：
18 pages, 11 figures, accepted in MNRAS
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摘要：

利用不变流形研究了银河系内部的棒驱动动力学。这个理论已经成功地应用于描述外部星系中的环和螺旋的形态和运动学，现在，我们第一次将其应用于银河系。我们计算位于杆端的不稳定周期轨道的不变流形所限定的轨道。我们讨论是否COBE/DIRBE酒吧和长酒吧组成一个单一的酒吧或两个独立的酒吧，并进行了一些比较，一起，强烈主张前者。更具体地说，我们倾向于这样的可能性，即所谓的COBE/DIRBE棒是一个棒的方形/花生状凸起，其外部薄的部分是所谓的长棒。这种可能性与外部星系的观测、轨道结构理论和模拟都很吻合。然后，我们详细分析了五个代表性的银河系潜力的形态和运动学。两个有一个费勒斯酒吧，两个有一个四极杆和最后一个复合酒吧。我们首先只考虑COBE/DIRBE条，然后将其扩展到包括长条的效果。我们发现，由流形给出的大尺度结构描述了一个内环，其大小类似于近和远3-kpc臂，和一个外环，其性质类似于银河系分子环。我们还分析了这两种结构的运动学，在不同的银河系势，并发现他们再现的主要超密度发现在银河系的速度CO图。最后，我们考虑在什么样的模型参数下，流形的全局形态可以再现两个外旋臂。我们的结论是，这将需要更大的质量和更迅速的旋转棒，或包括在潜在的额外的组件描述的螺旋臂。

英文摘要：

We study the bar-driven dynamics in the inner part of the Milky Way by using invariant manifolds. This theory has been successfully applied to describe the morphology and kinematics of rings and spirals in external galaxies, and now, for the first time, we apply it to the Milky Way. We compute the orbits confined by the invariant manifolds of the unstable periodic orbits located at the ends of the bar. We discuss whether the COBE/DIRBE bar and the Long bar compose a single bar or two independent bars and perform a number of comparisons which, taken together, argue strongly in favour of the former. More specifically, we favour the possibility that the so-called COBE/DIRBE bar is the boxy/peanut bulge of a bar whose outer thin parts are the so-called Long bar. This possibility is in good agreement both with observations of external galaxies, with orbital structure theory and with simulations. We then analyse in detail the morphology and kinematics given by five representative Galactic potentials. Two have a Ferrers bar, two have a quadrupole bar and the last one a composite bar. We first consider only the COBE/DIRBE bar and then extend it to include the effect of the Long bar. We find that the large-scale structure given by the manifolds describes an inner ring, whose size is similar to the near and far 3-kpc arm, and an outer ring, whose properties resemble those of the Galactic Molecular Ring. We also analyse the kinematics of these two structures, under the different galactic potentials, and find they reproduce the main over-densities found in the galactic longitude-velocity CO diagram. Finally, we consider for what model parameters, the global morphology of the manifolds may reproduce the two outer spiral arms. We conclude that this would necessitate either more massive and more rapidly rotating bars, or including in the potential an extra component describing the spiral arms.

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