Gravity, Magnetic Field, and Turbulence: Relative Importance and Impact on Fragmentation in the Infrared Dark Cloud G34.43+00.24
Gravity, Magnetic Field, and Turbulence: Relative Importance and Impact on Fragmentation in the Infrared Dark Cloud G34.43+00.24
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DOI：
10.3847/1538-4357/ab1484
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发表时间：
2019-03
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影响因子：
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通讯作者：
Ya-wen Tang;P. Koch;N. Peretto;G. Novak;A. Duarte-Cabral;N. Chapman;P. Hsieh;Hsi-Wei Yen
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文献类型：
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作者：
Ya-wen Tang;P. Koch;N. Peretto;G. Novak;A. Duarte-Cabral;N. Chapman;P. Hsieh;Hsi-Wei Yen
本文研究了红外暗云G34.43 + 00.24核碎裂过程中磁场（B）、重力和湍流的相互作用。我们观察了G34.43上的磁场形态，用350 μ m的热尘埃极化追踪，角分辨率为10 ″（0.18 pc），并与N2H+穿过灯丝获得的运动学进行了比较。我们从N2 H+中导出局部速度梯度，跟踪天空平面中的运动，并与观测到的天空平面中的局部B场方向进行比较。发现B场取向垂直于细丝的长轴，朝向MM 1和MM 2脊，这表明B场可以将材料引导向细丝。朝向MM 3，B场取向看起来更平行于细丝并且与MM 3的细长芯对齐，指示B场的不同作用。除了一个大规模的东西向速度梯度，我们发现一个紧密的对齐之间的局部B场的方向和局部速度梯度朝着MM1/MM2脊。这种局部相关性表明气体运动受B场形态的影响，反之亦然。此外，随着N2H+的积分发射的增加，这种对准似乎变得更加接近，这可能表明越来越大的引力牵引使B场和气体运动越来越对准。我们分析和量化的B场，重力，湍流，和它们的相对重要性对MM1，MM2和MM3地区的各种技术在两个尺度上，一个较大的团块面积在2 pc的规模和较小的核心面积在0.6 pc的规模。虽然引力能、B场和湍流压力都从大尺度到小尺度有系统地增长，但这三种成分之间的比例在尺度上明显不同。我们建议，这种不同的相对重要性之间的B场，重力和湍流的规模驱动器，并解释了不同的碎片类型在subparsec尺度（没有碎片在MM1;对齐的碎片在MM2;聚集的碎片在MM3）。我们讨论了不确定性，微妙之处，我们的结论的鲁棒性，我们强调，需要多尺度联合分析，以了解这些系统中的动态。
We investigate the interplay between magnetic (B) field, gravity, and turbulence in the fragmentation process of cores within the filamentary infrared dark cloud G34.43+00.24. We observe the magnetic field morphology across G34.43, traced with thermal dust polarization at 350 μm with an angular resolution of 10″ (0.18 pc), and compare with the kinematics obtained from N2H+ across the filament. We derive local velocity gradients from N2H+, tracing motion in the plane of sky, and compare with the observed local B field orientations in the plane of sky. The B field orientations are found to be perpendicular to the long axis of the filament toward the MM1 and MM2 ridge, suggesting that the B field can guide material toward the filament. Toward MM3, the B field orientations appear more parallel to the filament and aligned with the elongated core of MM3, indicating a different role of the B field. In addition to a large-scale east–west velocity gradient, we find a close alignment between local B field orientations and local velocity gradients toward the MM1/MM2 ridge. This local correlation in alignment suggests that gas motions are influenced by the B field morphology or vice versa. Additionally, this alignment seems to become even closer with increasing integrated emission in N2H+, possibly indicating that a growing gravitational pull alignes the B field and gas motion more and more. We analyze and quantify B field, gravity, turbulence, and their relative importance toward the MM1, MM2, and MM3 regions with various techniques over two scales, a larger clump area at 2 pc scale and the smaller core area at 0.6 pc scale. While gravitational energy, B field, and turbulent pressure all grow systematically from large to small scale, the ratios among the three constituents clearly develop differently over scale. We propose that this varying relative importance between B field, gravity, and turbulence over scale drives and explains the different fragmentation types seen at subparsec scale (no fragmentation in MM1; aligned fragmentation in MM2; clustered fragmentation in MM3). We discuss uncertainties, subtleties, and the robustness of our conclusion, and we stress that a multiscale joint analysis is required to understand the dynamics in these systems.