The dynamical evolution of molecular clouds near the Galactic Centre – II. Spatial structure and kinematics of simulated clouds
The dynamical evolution of molecular clouds near the Galactic Centre – II. Spatial structure and kinematics of simulated clouds
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DOI：
10.1093/mnras/stz381
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发表时间：
2019-02
影响因子：
4.8
通讯作者：
J. Kruijssen;J. Dale;S. Longmore;D. Walker;J. Henshaw;S. Jeffreson;M. Petkova;A. Ginsburg;
中科院分区：
文献类型：
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作者：
J. Kruijssen;J. Dale;S. Longmore;D. Walker;J. Henshaw;S. Jeffreson;M. Petkova;A. Ginsburg;
星系中心分子云的演化被认为不同于星系盘，这是由于外部引力势的显著影响。我们提出了一套数值模拟的分子云轨道上的100 pc流的中央分子区（中央$\sim500$ pc的银河系）和描述其形态和运动学的演化响应的背景势和偏心轨道运动。我们发现，云的形状由强大的剪切和扭矩，潮汐和几何变形，并通过他们的通道通过轨道近心点。在我们的模拟中，这些机制控制云的大小，长宽比，位置角，对流结构，柱密度，速度色散，视线速度梯度，自旋角动量和运动学的复杂性。通过将这些预测与银河系中心“尘埃脊”上的云观测进行比较，我们发现我们的模拟自然地再现了广泛的关键观测形态和运动学特征，这些特征可以用很好理解的物理机制来解释。我们认为，吸积的气体云到星系的中心区域，旋转曲线翻转和潮汐场是完全压缩，伴随着变革的动力学变化的云，导致崩溃和星星的形成。这可以产生一个具有共同起点的云坍缩的演化过程，这标志着吸积到潮汐压缩区域或最近的近心点通道的时间。总之，这些过程可能自然地产生在许多（额外的）星系核中观察到的同步星爆。
The evolution of molecular clouds in galactic centres is thought to differ from that in galactic discs due to a significant influence of the external gravitational potential. We present a set of numerical simulations of molecular clouds orbiting on the 100-pc stream of the Central Molecular Zone (the central $\sim500$ pc of the Galaxy) and characterise their morphological and kinematic evolution in response to the background potential and eccentric orbital motion. We find that the clouds are shaped by strong shear and torques, by tidal and geometric deformation, and by their passage through the orbital pericentre. Within our simulations, these mechanisms control cloud sizes, aspect ratios, position angles, filamentary structure, column densities, velocity dispersions, line-of-sight velocity gradients, spin angular momenta, and kinematic complexity. By comparing these predictions to observations of clouds on the Galactic Centre 'dust ridge', we find that our simulations naturally reproduce a broad range of key observed morphological and kinematic features, which can be explained in terms of well-understood physical mechanisms. We argue that the accretion of gas clouds onto the central regions of galaxies, where the rotation curve turns over and the tidal field is fully compressive, is accompanied by transformative dynamical changes to the clouds, leading to collapse and star formation. This can generate an evolutionary progression of cloud collapse with a common starting point, which either marks the time of accretion onto the tidally-compressive region or of the most recent pericentre passage. Together, these processes may naturally produce the synchronised starbursts observed in numerous (extra)galactic nuclei.