The geometry of the gas surrounding the Central Molecular Zone: on the origin of localized molecular clouds with extreme velocity dispersions
The geometry of the gas surrounding the Central Molecular Zone: on the origin of localized molecular clouds with extreme velocity dispersions
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DOI：
10.1093/mnras/stz2054
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发表时间：
2019-06
影响因子：
4.8
通讯作者：
M. Sormani;R. Tress;S. Glover;R. Klessen;A. Barnes;C. Battersby;P. Clark;H. P. Hatchfield;Rowan J. Smith
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文献类型：
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作者：
M. Sormani;R. Tress;S. Glover;R. Klessen;A. Barnes;C. Battersby;P. Clark;H. P. Hatchfield;Rowan J. Smith
银河系中心附近的分子气体观测（|L| < 10°，|B| < 1°）揭示了一个独特的人口神秘的致密云的存在，其特征是极端的速度分散（$\Delta v \gt 100\，{\rm km\，s^{-1}}$）。这些扩展的速度特征在数据立方体中非常突出，并主导了中央分子区（CMZ）外分子气体的运动学。这种云的典型例子是Bania Clump 2。我们表明，类似的功能自然产生的模拟气流在一个现实的禁止潜在的。我们分析了模拟中获得的特征结构，并以此来解释观测结果。我们发现，这些特征来自于物质之间的碰撞，这些物质沿着银河棒的尘埃带沿着快速下落，而这些物质属于以下两类之一：（i）在落在尘埃带的另一侧后“过冲”的物质;（ii）CMZ的一部分。这两种类型的碰撞都涉及到视线速度差异很大的气体，这就是产生观察到的极端速度分散的原因。这两类的例子可以在意见中找到。如果我们的解释是正确的，我们直接见证了（a）相对速度为$\sim 200\，{\rm km\，s^{-1}}$的云的碰撞和（B）新鲜气体在CMZ上的吸积过程。
Observations of molecular gas near the Galactic Centre (|l| < 10°, |b| < 1°) reveal the presence of a distinct population of enigmatic compact clouds that are characterized by extreme velocity dispersions ($\Delta v \gt 100\, {\rm km\, s^{-1}}$). These extended velocity features are very prominent in the data cubes and dominate the kinematics of molecular gas just outside the Central Molecular Zone (CMZ). The prototypical example of such a cloud is Bania Clump 2. We show that similar features are naturally produced in simulations of gas flow in a realistic barred potential. We analyse the structure of the features obtained in the simulations and use this to interpret the observations. We find that the features arise from collisions between material that has been infalling rapidly along the dust lanes of the Milky Way bar and material that belongs to one of the following two categories: (i) material that has ‘overshot’ after falling down the dust lanes on the opposite side; (ii) material which is part of the CMZ. Both types of collisions involve gas with large differences in the line-of-sight velocities, which is what produces the observed extreme velocity dispersions. Examples of both categories can be identified in the observations. If our interpretation is correct, we are directly witnessing (a) collisions of clouds with relative speeds of $\sim 200\, {\rm km\, s^{-1}}$ and (b) the process of accretion of fresh gas onto the CMZ.