论文标题

分子云的重力碎片期间集线器系统的动能和磁能预算

The kinetic and magnetic energy budget of hub-filament systems during the gravitational fragmentation of molecular clouds

论文作者

Camacho, Vianey, Vázquez-Semadeni, Enrique, Zamora-Avilés, Manuel, Palau, Aina

论文摘要

我们介绍了对引力(例如),动力学(EK)和磁性(EM)能量之间在集线器丝系统内的结构的平衡的数值研究,这是对巨型分子云的形成和全局层次塌陷(GHC)的模拟。对于由各种密度阈值定义的结构,在不同的进化阶段,我们调查病毒式参数的缩放,$α$,带质量$ m $,$ m $,$ {\ cal {l}} \equivσ_v/rev/r^{1/2} $,$ n $ nes $ nes $ nes $ nes $,是一个有效的半径。我们还研究了相应的磁参数$α_m$和$ {\ cal {l}} _ m $的这些量表。最后,我们将数值结果与大量团块的观察样本进行了比较。我们发现:1)$α_m$和$ {\ cal {l}} _ m $遵循与它们的动力学相似的量表,尽管比率em/ek降低为| eg |增加。 2)最大的物体是由最低阈值定义的,倾向于在重力结合(磁性超临界),而其内部子结构往往显得未结束(和亚临界)。这表明后者是由其母体结构的插座压缩的,并支持了早期的建议:在理想MHD下,测得的质量与磁通量比$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $。 3)〜$α$ - $ m $和$ {\ cal {l}} $ - $σ$图中的散布在直接反对EG绘制时减少了$σ$图,这表明散点是由于质量和大小之间的模棱两可。 4)我们的GHC模拟中的团块遵循与$α$ - $ m $和$ {\ cal {l}} $ - $σ$图的观察样本相同的趋势。我们得出的结论是,结构中能量预算的主要控制参数是例如,动力和磁能是从中得出的。

We present a numerical study of the balance between the gravitational (Eg), kinetic (Ek), and magnetic (Em) energies of structures within a hub-filament system in a simulation of the formation and global hierarchical collapse (GHC) of a giant molecular cloud. For structures defined by various density thresholds, and at different evolutionary stages, we investigate the scaling of the virial parameter, $α$, with mass $M$, and of the Larson ratio, ${\cal{L}}\equivσ_v/R^{1/2}$, with column density $Σ$, where $σ_v$ is the 1D velocity dispersion, and $R$ is an effective radius. We also investigate these scalings for the corresponding magnetic parameters $α_m$ and ${\cal{L}}_m$. Finally, we compare our numerical results with an observational sample of massive clumps. We find that: 1) $α_m$ and ${\cal{L}}_m$ follow similar scalings as their kinetic counterparts, although the ratio Em/Ek decreases as |Eg| increases. 2) The largest objects, defined by the lowest thresholds, tend to appear gravitationally bound (and magnetically supercritical), while their internal substructures tend to appear unbound (and subcritical). This suggests that the latter are being compressed by the infall of their parent structures, and supports earlier suggestions that the measured mass-to-magnetic flux ratio $μ$ decreases inwards in a centrally-peaked cloud under ideal MHD. 3)~The scatter in the $α$-$M$ and ${\cal{L}}$-$Σ$ plots is reduced when Ek and Em are plotted directly against Eg, suggesting that the scatter is due to an ambiguity between mass and size. 4) The clumps in our GHC simulation follow the same trends as the observational sample of massive clumps in the $α$-$M$ and ${\cal{L}}$-$Σ$ diagrams. We conclude that the main controlling parameter of the energy budget in the structures is Eg, with the kinetic and magnetic energies being derived from it.

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