Dense Gas Kinematics and a Narrow Filament in the Orion A OMC1 Region Using NH3
Dense Gas Kinematics and a Narrow Filament in the Orion A OMC1 Region Using NH3
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DOI：
10.3847/1538-4357/aac8da
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发表时间：
2018-06
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通讯作者：
Kristina Monsch;J. Pineda;H. Liu;C. Zucker;H. Chen;K. Pattle;S. Offner;J. di Francesco;A. Ginsburg;B. Ercolano;H. Arce;R. Friesen;H. Kirk;P. Caselli;A. Goodman
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作者：
Kristina Monsch;J. Pineda;H. Liu;C. Zucker;H. Chen;K. Pattle;S. Offner;J. di Francesco;A. Ginsburg;B. Ercolano;H. Arce;R. Friesen;H. Kirk;P. Caselli;A. Goodman
我们提出了由 Karl G. Jansky 甚大阵列和 100 m Robert C. Byrd Green Bank 望远镜获得的猎户座 A 中向 OMC1 的 (J, K) = (1, 1) 和 (2, 2) 反演跃迁的综合观测结果。这些观测结果的角分辨率为 6 英寸（0.01 pc），以前所未有的细节揭示了复杂的丝状结构，该结构延伸到活动猎户座 BN/KL 区域以北的覆盖范围约为 6′ × 7′ 的区域。我们在 OMC1 内发现了 0.012 pc 宽的细丝，长宽比为 ∼37:1，这在之前的研究中被遗漏了。它的方向直接与猎户座 A 中詹姆斯·克拉克·麦克斯韦望远镜 BISTRO 巡天的磁场相对方向进行比较。我们发现细丝的平均方向和磁场之间有约 11° 的小偏差，表明它们几乎彼此平行。据估计，这种细丝的柱密度比赫歇尔研究的细丝大 2-3 个数量级，并且考虑到发现的湍流值较低，它可能具有自引力。我们通过对 (J, K) = (1, 1) 和 (2, 2) 线的超精细结构进行正向建模，进一步生成气体运动学图。由此产生的速度弥散分布在 ~0.5 km s−1 处达到峰值，接近气体的亚音速状态。该值比之前在同一区域的单碟观测中测得的值小约 0.2 km s−1 ，这表明更高的角度和光谱分辨率观测将识别出甚至更低的速度色散，可能达到致密气体细丝中的亚音速湍流状态。
We present combined observations of the (J, K) = (1, 1) and (2, 2) inversion transitions toward OMC1 in Orion A obtained by the Karl G. Jansky Very Large Array and the 100 m Robert C. Byrd Green Bank Telescope. With an angular resolution of 6″ (0.01 pc), these observations reveal with unprecedented detail the complex filamentary structure extending north of the active Orion BN/KL region in a field covering ∼6′ × 7′. We find a 0.012 pc wide filament within OMC1, with an aspect ratio of ∼37:1, that was missed in previous studies. Its orientation is directly compared to the relative orientation of the magnetic field from the James Clerk Maxwell Telescope BISTRO survey in Orion A. We find a small deviation of ∼11° between the mean orientation of the filament and the magnetic field, suggesting that they are almost parallel to one another. The filament’s column density is estimated to be 2–3 orders of magnitude larger than the filaments studied with Herschel and is possibly self-gravitating, given the low values of turbulence found. We further produce maps of the gas kinematics by forward modeling the hyperfine structure of the (J, K) = (1, 1) and (2, 2) lines. The resulting distribution of velocity dispersions peaks at ∼0.5 km s−1, close to the subsonic regime of the gas. This value is about 0.2 km s−1 smaller than previously measured in single-dish observations of the same region, suggesting that higher angular and spectral resolution observations will identify even lower velocity dispersions that might reach the subsonic turbulence regime in dense gas filaments.