Spitzer spectral line mapping of the HH211 outflow
Spitzer spectral line mapping of the HH211 outflow
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HH211 外流的斯皮策谱线图
DOI：
10.1051/0004-6361/200913650
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
G. Forêts
中科院分区：
文献类型：
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作者：
O. Dionatos;O. Dionatos;B. Nisini;S. Cabrit;L. Kristensen;G. Forêts;G. Forêts
上下文。通过CO和SiO的谱线发射，来自最年轻的原恒星的喷流通常只在毫米波长被探测到。然而，目前尚不清楚这些喷流主要是分子还是原子，也不清楚它们是追踪喷出的气体还是嵌入的原子喷流周围的夹带层。目标。我们研究了HH_211原恒星流出的热气体含量，以评估以H_2形式存在的喷流质量通量，并调查嵌入的原子喷流的存在。方法：研究方法。我们使用档案斯皮策狭缝扫描观测了HH_211在5.2-37μm范围内的流出，这是用低分辨率红外光谱模块获得的。通过发射线诊断和现有的分子激波模型网格来解释检测到的分子和原子线。热气体的物理性质与其他分子喷流示踪剂以及L1448-C外流的类似研究结果进行了比较。结果。我们探测并绘制了v=0−0 S(0)-S(7)H2谱线以及S、Fe+、Si+的精细结构谱线。从源头探测到5��的H2，其特征是T∼为30 0K，T∼为10 0 0±30 0K，消光AV∼为8MAG。喷流中的冷氢气量与CO估计的完全分子气体的量一致。热分量与低束填充因子∼为0.0 1~0.0 4的C型激波有很好的拟合，其质量通量与冷的H2相似。精细结构线发射来自电离分数为∼0.5−5×10−3的致密气体，代表解离激波。与硫的线性比率表明，铁和硅相对于太阳丰度的贫化是∼的10-50倍。结论。斯皮策光谱映射观测首次显示出朝着HH_211的CO喷流的冷的H2成分，这与CO物质在�300K是完全分子的和热的一致。这些谱图还首次探测到嵌入在HH_211流出中的原子喷流，可以追踪到靠近中心源位置。它大量的铁和硅的消耗排除了原恒星周围尘埃升华带内的起源。尽管目前喷流速度和激波条件的不确定性太大，无法得出明确的结论，但动量通量似乎不足以卷绕CO喷流。
Context. Jets from the youngest protostars are often detected only at mm wavelengths, by means of line emission of CO and SiO. However, it is not yet clear whether these jets are mostly molecular or atomic, nor whether they trace ejected gas or an entrained layer around an embedded atomic jet. Aims. We investigate the warm gas content of the HH211 protostellar outflow to assess the jet mass-flux in the form of H2 and investigate the existence of an embedded atomic jet. Methods. We employ archival Spitzer slit-scan observations of the HH211 outflow over 5.2–37 μm obtained with the low resolution IRS modules. Detected molecular and atomic lines are interpreted by means of emission line diagnostics and an existing grid of molecular shock models. The physical properties of the warm gas are compared with those of other molecular jet tracers and to the results of a similar study towards the L1448-C outflow. Results. We detected and mapped the v = 0−0 S(0)–S(7) H2 lines as well as fine-structure lines of S, Fe + ,a nd Si + .T he H 2 is detected to 5 �� from the source and is characterized by a “cool” T ∼ 300 K and a “warm” T ∼ 1000 ± 300 K component, with an extinction AV ∼ 8 mag. The amount of cool H2 towards the jet agrees with that estimated from CO assuming fully molecular gas. The warm component is well fitted by C-type shocks with a low beam filling factor ∼0.01–0.04 and a mass-flux similar to the cool H2 .T he fine-structure line emission arises from dense gas with ionization fraction ∼0.5−5 × 10 −3 , and is indicative of dissociative shocks. Line ratios with respect to sulfur indicate that iron and silicon are depleted relative to solar abundances by a factor ∼10–50. Conclusions. Spitzer spectral mapping observations reveal for the first time a cool H2 component towards the CO jet of HH211 consistent with the CO material being fully molecular and warm at � 300 K. These maps detect also for the first time an embedded atomic jet in the HH211 outflow that can be traced close to the central source position. Its significant iron and silicon depletion excludes an origin from within the dust sublimation zone around the protostar. The momentum-flux seems insufficient to entrain the CO jet, although current uncertainties in jet speed and shock conditions are too large to reach a definite conclusion.