Extended warm gas in Orion KL as probed by methyl cyanide
Extended warm gas in Orion KL as probed by methyl cyanide
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DOI：
10.1051/0004-6361/201321872
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发表时间：
2014-02
影响因子：
6.5
通讯作者：
T. Bell;J. Cernicharo;S. Viti;N. Marcelino;A. Palau;G. Esplugues;B. Tercero
中科院分区：
文献类型：
--
作者：
T. Bell;J. Cernicharo;S. Viti;N. Marcelino;A. Palau;G. Esplugues;B. Tercero
为了研究猎户座Kleinmann-Low星云内扩展气体的温度分布，我们在平均角分辨率为10角秒的条件下，绘制了乙腈（CH_3CN）在J = 6 K ~ 5 K，J = 12 K ~ 11 K，J = 13 K ~ 12 K和J = 14 K ~ 13 K跃迁的辐射图（6 K 5 K线为22角秒），作为使用IRAM 30米望远镜对该地区进行新的二维线测量的一部分。这些完全采样的地图显示了IRc 2东北部温暖气体的延伸排放以及热核和致密脊源组件的独特运动学特征。我们已经构建了人口图的四套K-阶梯发射线在每个位置的地图，并已推导出旋转激发温度和总梁平均柱密度从拟合的斜率。此外，我们还将LVG模型光谱与观测结果进行了拟合，以确定每个地图位置的最佳物理参数，从而得出整个区域的动力学温度分布。由此产生的温度图揭示了一个区域的热（T > 350 K）的材料周围的东北边缘的热核，而柱密度分布更均匀，并在IRc 2的位置附近的峰值。我们将这一区域的热气归因于该区域活跃星星形成过程中流出物质的冲击加热，如宽CH 3CN线所示。这种情况是一致的预测，从C-冲击化学模型表明，气相乙腈生存在冲击后的气体，可以在一定程度上增强由于溅射的谷物地幔在通过冲击前。
In order to study the temperature distribution of the extended gas within the Orion Kleinmann-Low nebula, we have mapped the emission by methyl cyanide (CH3CN) in its J = 6K 5K, J = 12K 11K, J = 13K 12K, and J = 14K 13K transitions at an average angular resolution of 10 arcsec (22 arcsec for the 6K 5K lines), as part of a new 2D line survey of this region using the IRAM 30 m telescope. These fully sampled maps show extended emission from warm gas to the northeast of IRc2 and the distinct kinematic signatures of the hot core and compact ridge source components. We have constructed population diagrams for the four sets of K-ladder emission lines at each position in the maps and have derived rotational excitation temperatures and total beam-averaged column densities from the fitted slopes. In addition, we have fitted LVG model spectra to the observations to determine best-fit physical parameters at each map position, yielding the distribution of kinetic temperatures across the region. The resulting temperature maps reveal a region of hot (T > 350 K) material surrounding the north-eastern edge of the hot core, whereas the column density distribution is more uniform and peaks near the position of IRc2. We attribute this region of hot gas to shock heating caused by the impact of outflowing material from active star formation in the region, as indicated by the presence of broad CH3CN lines. This scenario is consistent with predictions from C-shock chemical models that suggest that gas-phase methyl cyanide survives in the post-shock gas and can be somewhat enhanced due to sputtering of grain mantles in the passing shock front.