On the Nature of Orion Source I
On the Nature of Orion Source I
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DOI：
10.3847/1538-4357/aaa24b
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发表时间：
2018-01
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通讯作者：
A. Baez--Rubio-A.-Baez--Rubio-1388382687;I. Jiménez-Serra;Jesús Martín-Pintado;Qizhou Zhang;S. Curiel
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作者：
A. Baez--Rubio-A.-Baez--Rubio-1388382687;I. Jiménez-Serra;Jesús Martín-Pintado;Qizhou Zhang;S. Curiel
猎户座中的克莱曼低星云是距离大质量星星形成最近的区域，它是源I的所在地，源I的性质还在争论之中。这个来源的知识可能对我们理解猎户座KL热核的能量学有深远的影响，因为它可能是该地区的主要热源。这个源在射电中的光谱能量分布的特征是接近2的正光谱指数，这与（i）由中心大质量原恒星产生的电离氢气的热韧致辐射，或（ii）由电子在与中性和分子氢的相互作用下偏转时产生的光球韧致辐射相一致。如果电离的氢气是观测到的连续发射的原因，那么它的模型将预测氢无线电复合线（RRL）的可检测发射。然而，我们的SMA观测是以足够高的灵敏度获得的，可以排除射电连续辐射来自致密超致密H ii区，因为与我们的观测相反，H26α线已经被检测到。为了解释观测限制，我们进一步研究了源I的射电连续辐射的性质。我们已经比较了现有的无线电连续数据与我们升级的非LTE 3D辐射传输模型的预测，MODEL的REcombination线，表明无线电连续通量和大小只能通过假设尘埃和韧致辐射从中性气体的排放再现。在ν ≥ 43 GHz处，尘埃辐射贡献显著。此外，我们的RRL峰值强度的电离金属的情况下的预测是一致的Na和K RRL在毫米和亚毫米波长的非检测。
The Kleinmann–Low nebula in Orion, the closest region of massive star formation, harbors Source I, whose nature is under debate. Knowledge of this source may have profound implications for our understanding of the energetics of the hot core in Orion KL since it might be the main heating source in the region. The spectral energy distribution of this source in the radio is characterized by a positive spectral index close to 2, which is consistent with (i) thermal bremsstrahlung emission of ionized hydrogen gas produced by a central massive protostar, or (ii) photospheric bremsstrahlung emission produced by electrons when deflected by the interaction with neutral and molecular hydrogen like Mira-like variable stars. If ionized hydrogen gas were responsible for the observed continuum emission, its modeling would predict detectable emission from hydrogen radio recombination lines (RRLs). However, our SMA observations were obtained with a high enough sensitivity to rule out that the radio continuum emission arises from a dense hypercompact H ii region because the H26α line would have been detected, in contrast with our observations. To explain the observational constraints, we investigate further the nature of the radio continuum emission from source I. We have compared available radio continuum data with the predictions from our upgraded non-LTE 3D radiative transfer model, MOdel for REcombination LInes, to show that radio continuum fluxes and sizes can only be reproduced by assuming both dust and bremsstrahlung emission from neutral gas. The dust emission contribution is significant at ν ≥ 43 GHz. In addition, our RRL peak intensity predictions for the ionized metals case are consistent with the nondetection of Na and K RRLs at millimeter and submillimeter wavelengths.