论文标题
Silcc-Zoom：分子云子结构的动态平衡
SILCC-Zoom: the dynamic balance in molecular cloud substructures
论文作者
论文摘要
分子云如何碎片并创建形成恒星的密集结构是一个悬而未决的问题。我们研究了基于SILCC-Zoom模拟的分子云及其子结构的形成和演化，研究了不同能量项（动力学，热，磁性和重力）的相对重要性。这些模拟遵循从分层的银河盘中从弥漫性超新星驱动的星际介质中的冷分子云的自洽形成到0.1 pc的尺度。我们研究了1.5-2 MYR的七个分子云（五个带有磁场的五个）的时间演变。使用树状图，我们识别云中层次结构的3D子结构，目的是了解其动力学并区分gravel脉腐烂碎片的理论和全局层次层崩溃。病毒分析表明，致密气体确实由重力和湍流相互作用，而磁场和热压仅对蓬松的原子结构很重要。随着时间的流逝，重力结合的子结构从边缘结合的培养基（病毒比$ 1 \leqα_{\ rm vir}^{\ rm vol} <2 $）出现，这是大规模超级诺瓦 - 超级诺瓦驱动的流入的结果。详细的潮汐分析表明，潮汐张量高度各向异性。然而，潮汐力通常不足以破坏大规模或密集的子结构，但会导致其变形。通过比较潮汐和交叉时间尺度，我们发现潮汐力似乎不是分子云中湍流的主要驱动力。
How molecular clouds fragment and create the dense structures which go on to form stars is an open question. We investigate the relative importance of different energy terms (kinetic, thermal, magnetic, and gravity - both self-gravity and tidal forces) for the formation and evolution of molecular clouds and their sub-structures based on the SILCC-Zoom simulations. These simulations follow the self-consistent formation of cold molecular clouds down to scales of 0.1 pc from the diffuse supernova-driven interstellar medium in a stratified galactic disc. We study the time evolution of seven molecular clouds (five with magnetic fields and two without) for 1.5-2 Myr. Using a dendrogram, we identify hierarchical 3D sub-structures inside the clouds with the aim to understand their dynamics and distinguish between the theories of gravo-turbulent fragmentation and global hierarchical collapse. The virial analysis shows that the dense gas is indeed dominated by the interplay of gravity and turbulence, while magnetic fields and thermal pressure are only important for fluffy, atomic structures. Over time, gravitationally bound sub-structures emerge from a marginally bound medium (viral ratio $1 \leq α_{\rm vir}^{\rm vol} <2$) as a result of large-scale supernova-driven inflows rather than global collapse. A detailed tidal analysis shows that the tidal tensor is highly anisotropic. Yet the tidal forces are generally not strong enough to disrupt either large-scale or dense sub-structures but cause their deformation. By comparing tidal and crossing time scales, we find that tidal forces do not seem to be the main driver of turbulence within the molecular clouds.
