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arXiv 1702.01646astro-ph.GA
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Milky Way型星系中棒的形成

Bar formation in the Milky Way type galaxies

E. V. Polyachenko, P. Berczik, A. Just

摘要:

许多棒星系,可能包括银河系,在中心有尖点。然而,有一种普遍的看法认为,在无凸起星系模型中发生的通常的棒不稳定性对于尖点模型是不可能的,因为任何模式速度都存在内部林德布拉德共振。同时也有数值证据表明,杆的失稳可以形成杆。我们分析这种差异,准确和多样的N体模拟和使用正常模式的计算。我们表明,酒吧的形成,在尖状星系可以解释考虑盘的厚度。指数增长的时间是温和的典型的电流盘群众(约2.5亿年),但大大增加(因子2或更多)后,取代的活晕和隆起与刚性晕/隆起的潜力,同时模式的速度几乎保持不变。正常模式分析与不同的光盘质量赞成一个年轻的酒吧假设,根据该酒吧不稳定饱和最近。

英文摘要:

Many barred galaxies, possibly including the Milky Way, have cusps in the centres. There is a widespread belief, however, that usual bar instability taking place in bulgeless galaxy models is impossible for the cuspy models, because of the presence of the inner Lindblad resonance for any pattern speed. At the same time there are numerical evidences that the bar instability can form a bar. We analyse this discrepancy, by accurate and diverse N-body simulations and using the calculation of normal modes. We show that bar formation in cuspy galaxies can be explained by taking into account the disc thickness. The exponential growth time is moderate for typical current disc masses (about 250 Myr), but considerably increases (factor 2 or more) upon substitution of the live halo and bulge with a rigid halo/bulge potential; meanwhile pattern speeds remain almost the same. Normal mode analysis with different disc mass favours a young bar hypothesis, according to which the bar instability saturated only recently.

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