Tracing the Shock Precursors in the L1448-mm/IRS 3 Outflows
Tracing the Shock Precursors in the L1448-mm/IRS 3 Outflows
复制标题
追踪 L1448-mm/IRS 3 流出中的冲击前兆
DOI：
10.1086/382784
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
N. Marcelino
中科院分区：
文献类型：
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作者：
I. Jímenez;J. Martín;A. Rodríguez;N. Marcelino
本文介绍了在L1448-mm和L1448 IRS 3中，在环境速度下，对SiO ν = 0，J = 2-1和J = 3-2谱线以及HCO 101-000，J = 3 - 2-1/2，F = 2-1谱线的探测。这是第一次在暗云中探测到HCO。我们还测量了H_（13）CO ~+、H_（13）CN、HN_（13）C、CH_3OH和N_2 H ~+的谱线。虽然HCO和SiO线具有线宽为~0.5 km s-1的偏西轮廓，但其他线的宽度为~1 km s-1。朝向L1448-mm，除了SiO和HCO的那些线之外，所有的线都显示出以4.7和5.2 km s-1为中心的两个不同的速度分量。HCO只在4.7 km s-1的云中观测到，SiO只在5.2 km s-1的云中观测到。在5.2 km s-1的云中，SiO的丰度约为10-11，比4.7 km s-1的云和其它暗云中的SiO丰度大1个数量级。HCO的丰度约为10-11，类似于暗云中静止气体的离子-分子反应模型所预测的丰度。SiO/HCO丰度比从4.7到5.2 km s-1的变化很大（>150），SiO向L1448-mm方向发射的分布和运动学表明，环境SiO与分子外流有关。我们认为，窄线宽和环境气体中的SiO的丰度产生的相互作用的磁和/或辐射的冲击与cluerically presparked环境气体的前兆。
We present the detection of the SiO ν = 0, J = 2-1, and J = 3-2 lines and of the HCO 101-000, J = 3/2-1/2, F = 2-1 line at ambient velocities toward the molecular outflows in L1448-mm and L1448 IRS 3. This is the first detection of HCO in a dark cloud. We have also measured lines of H13CO+, H13CN, HN13C, CH3OH, and N2H+. While the HCO and the SiO lines have the narrowest profiles with line widths of ~0.5 km s-1, the other lines have widths of ~1 km s-1. Toward L1448-mm, all lines except those of SiO and HCO show two distinct velocity components centered at 4.7 and 5.2 km s-1. HCO is only observed in the 4.7 km s-1 cloud and SiO in the 5.2 km s-1 component. The SiO abundance is ~10-11 in the 5.2 km s-1 clouds, 1 order of magnitude larger than in the 4.7 km s-1 component and in other dark clouds. The HCO abundance is ~10-11, similar to that predicted by the ion-molecule reactions models for the quiescent gas in dark clouds. The large change in the SiO/HCO abundance ratio (>150) from the 4.7 to the 5.2 km s-1 component, and the distribution and kinematics of the SiO emission toward L1448-mm suggest that the ambient SiO is associated with the molecular outflows. We propose that the narrow line widths and the abundances of SiO in the ambient gas are produced by the interaction of the magnetic and/or radiative precursors of the shocks with the clumpy preshocked ambient gas.