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arXiv 1909.02570astro-ph.GA
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反向旋转暗物质晕中的星棒:晕轨道反转的作用

Stellar Bars in Counter-Rotating Dark Matter Halos: The Role of Halo Orbit Reversals

Angela Collier, Isaac Shlosman, Clayton Heller

摘要:

盘星系可以与其宿主暗物质(DM)晕交换角动量和重子。这些晕具有内部自旋,“旋”,这是微不足道的旋转,但影响重子和DM组件之间的相互作用。虽然目前还没有星系中逆时针和逆时针旋转晕的统计数据,但这种晕的存在对星系演化很重要。在以往的工作中,我们分析了在旋晕中恒星棒的动力学和长期演化以及DM对棒扰动的响应,发现棒和DM晕轨道之间的共振相互作用对它进行了修正。在目前的工作中,我们遵循恒星酒吧逆行晕的演变。我们发现,这种演变与文献中讨论的刚性无反应晕的演变有很大不同。首先,我们确认,酒吧不稳定性延迟逐步沿逆行的“λ”序列。第二,在逆行晕酒吧的演变也不同于在逆时针晕,在酒吧继续大幅增长超过10 Gyr的模拟时间。DM的反应也大大弱于这种反应的晕圈。第三,通过对DM轨道结构的轨道谱分析,我们发现了一种我们称之为轨道反转的现象-当逆行DM轨道与恒星棒相互作用时,它们的流动和岁差发生逆转,变成逆行DM轨道。这一过程控制了棒附近的内晕区域,并允许这些轨道被棒捕获,从而提高了由内林德布拉德共振传递角动量的效率。我们在一些例子中明确地证明了这种逆转过程。

英文摘要:

Disk galaxies can exchange angular momentum and baryons with their host dark matter (DM) halos. These halos possess internal spin, `lambda', which is insignificant rotationally but does affect interactions between the baryonic and DM components. While statistics of prograde and retrograde spinning halos in galaxies is not available at present, the existence of such halos is important for galaxy evolution. In the previous works, we analyzed dynamical and secular evolution of stellar bars in prograde spinning halos and the DM response to the bar perturbation, and found that it is modified by the resonant interactions between the bar and the DM halo orbits. In the present work, we follow the evolution of stellar bars in retrograde halos. We find, that this evolution differs substantially from evolution in rigid unresponsive halos, discussed in the literature. First, we confirm that the bar instability is delayed progressively along the retrograde `lambda' sequence. Second, the bar evolution in the retrograde halos differs also from that in the prograde halos, in that the bars continue to grow substantially over the simulation time of 10 Gyr. The DM response is also substantially weaker compared to this response in the prograde halos. Third, using orbital spectral analysis of the DM orbital structure, we find a phenomenon we call the orbit reversal --- when retrograde DM orbits interact with the stellar bar, reverse their streaming and precession, and become prograde. This process dominates the inner halo region adjacent to the bar and allows these orbits to be trapped by the bar, thus increasing efficiency of angular momentum transfer by the Inner Lindblad Resonance. We demonstrate this reversal process explicitly in a number of examples.

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