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arXiv 1404.6038astro-ph.SR
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对双受阻星云的详细分子观测

Detailed molecular observations toward the Double Helix Nebula

K. Torii, R. Enokiya, M. R. Morris, K. Hasegawa, N. Kudo, Y. Fukui

备注：
36 pages, 17 figures, 1 table, accepted to ApJS
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摘要：

位于银河系中心（GC）的Sgr A* 上方100 pc的双受阻星云（DHN）是一个独特的结构，其形态表明它是一个磁性特征（Morris，Uchida & Do 2006）。Enokiya等人（2014）最近对DHN的分子观测揭示了DHN在径向速度为-35 km/s和0 km/s时的两个候选分子对应物，并讨论了DHN起源于GC中的环核盘的模型。本文介绍了利用CSO和Mopra望远镜对DHN进行的新的CO观测。1 pc尺度的高分辨率观测揭示了两个CO对应物（0 km/s和-35 km/s特征）的详细分布和运动学特征，并提供了有关其物理条件的新信息。结果，我们发现0 km/s质量为3.3x10^4 Msun的特征与DHN的红外发射相吻合，表明与DHN有明显的关联。与0 km/s特征相比，-35 km/s特征（质量为0.8x10^4 Msun）的关联不太清楚，但分子气体和DHN之间的互补分布以及沿DHN的速度变化支持其与DHN的关联。这两种分子特征是高度激发的，如由相对高的CO J=2-1/J=1-0强度比~1.0所示，并且具有~30 K的动力学温度，与GC中的典型分子云一致。

英文摘要：

The Double Helix Nebula (DHN), located 100 pc above Sgr A* in the Galactic center (GC), is a unique structure whose morphology suggests it is a magnetic feature (Morris, Uchida & Do 2006). Recent molecular observations toward the DHN by Enokiya et al. (2014) revealed two candidate molecular counterparts of the DHN at radial velocities of -35 km/s and 0 km/s and discussed the model in which the DHN has its origin at the circumnuclear disk in the GC. In this paper, new CO observations toward the DHN using the CSO and Mopra telescopes are presented. The higher-resolution observations of ~1 pc scale reveal the detailed distributions and kinematics of the two CO counterparts (the 0 km/s and -35 km/s features) and provide new information on their physical conditions. As a result, we find that the 0 km/s feature with a mass of 3.3x10^4 Msun coincides with the infrared emission of the DHN, indicating clear association with the DHN. The association of the -35 km/s feature, with a mass of 0.8x10^4 Msun, is less clear compared with the 0 km/s feature, but the complementary distribution between the molecular gas and the DHN and velocity variation along the DHN support its association with the DHN. The two molecular features are highly excited, as shown by the relatively high CO J=2-1/J=1-0 intensity ratios of ~1.0, and have kinetic temperatures of ~30 K, consistent with the typical molecular clouds in the GC.

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