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arXiv 1212.2018astro-ph.GA
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NGC 2068稠密气体的结构和运动学

The structure and kinematics of dense gas in NGC 2068

S. L. Walker-Smith, J. S. Richer, J. V. Buckle, R. J. Smith, J. S. Greaves, I. A. Bonnell

摘要:

我们用JCMT上的HARP,在~(13)CO和C ~(18)O(J = 3-2)及H ~(13)CO ~+(J = 4-3)谱线上,对猎户座B分子云中的NGC 2068区进行了观测。我们使用13 CO来绘制该地区的外流,并将其与先前定义的SCUBA核心相匹配。我们将C_(18)O和H_(13)CO ~+分解成高斯簇,分别找到26个和8个簇。C18 O和H13 CO+的平均去卷积半径分别为6200 +/- 2000 AU和3600 +/- 900 AU。我们还计算了这些团簇的维里和气体质量,从而确定了它们的结合程度。我们发现,C18 O团块比H13 CO+团块更受约束(平均气体质量维里质量比为4.9比1.4)。我们测量的C18 O和H13 CO+的团块内部速度色散分别为0.28 +/- 0.02 kms-1和0.27 +/- 0.04 kms-1,尽管H13 CO+的值被原恒星的大多数团块严重加权,因此具有固有的更大的线宽。我们认为,无星团块对应于当地的湍流最小值,我们发现,我们的团块是一致的重力湍流碎片形成。我们还计算了C18 O和H13 CO+的团间速度分散度分别为0.39 +/- 0.05 kms-1和0.28 +/- 0.08 kms-1。我们的团块的速度分散(内部和外部)与分子云中衰减湍流的数值模拟结果相匹配。然而,由于我们的样本规模较小,仍然没有足够的证据来最终确定湍流的类型和恒星形成的时间尺度。

英文摘要:

We have carried out a survey of the NGC 2068 region in the Orion B molecular cloud using HARP on the JCMT, in the 13CO and C18O (J = 3-2) and H13CO+ (J = 4-3) lines. We used 13CO to map the outflows in the region, and matched them with previously defined SCUBA cores. We decomposed the C18O and H13CO+ into Gaussian clumps, finding 26 and 8 clumps respectively. The average deconvolved radii of these clumps is 6200 +/- 2000 AU and 3600 +/- 900 AU for C18O and H13CO+ respectively. We have also calculated virial and gas masses for these clumps, and hence determined how bound they are. We find that the C18O clumps are more bound than the H13CO+ clumps (average gas mass to virial mass ratio of 4.9 compared to 1.4). We measure clump internal velocity dispersions of 0.28 +/- 0.02 kms-1 and 0.27 +/- 0.04 kms-1 for C18O and H13CO+ respectively, although the H13CO+ values are heavily weighted by a majority of the clumps being protostellar, and hence having intrinsically greater linewidths. We suggest that the starless clumps correspond to local turbulence minima, and we find that our clumps are consistent with formation by gravoturbulent fragmentation. We also calculate inter-clump velocity dispersions of 0.39 +/- 0.05 kms-1 and 0.28 +/- 0.08 kms-1 for C18O and H13CO+ respectively. The velocity dispersions (both internal and external) for our clumps match results from numerical simulations of decaying turbulence in a molecular cloud. However, there is still insufficient evidence to conclusively determine the type of turbulence and timescale of star formation, due to the small size of our sample.

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