Infall Signatures in Spectral Line Profiles of Protostellar Envelopes
Infall Signatures in Spectral Line Profiles of Protostellar Envelopes
复制标题
原恒星包层谱线剖面的坠落特征
DOI：
10.1086/308901
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
S. Inutsuka
中科院分区：
文献类型：
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作者：
H. Masunaga;S. Inutsuka
分子线谱中具有更强蓝色峰的双峰轮廓被认为是原恒星周围气体包层中坠落运动的有力证据。过去的一些研究使用简化的动力学模型（例如等温相似解）进行模型计算，以重现观察到的光谱轮廓。然而，谱线合成的相似解的有效性应该与更现实的动力学模型进行比较来检验。在本文中，我们采用来自作者最近工作的原恒星形成的球对称辐射流体动力学模型，对分子线谱进行了理论建模。这项研究的重点是坠落运动如何解释观察到的原恒星源的不对称线剖面。我们没有明确考虑旋转和流出对线轮廓生成的影响。在我们的非 LTE 线路传输的数字代码中，能级总体与球对称的任意物理结构下的辐射场完全一致，因此，可以实现可靠的谱合成，并与 LTE、大速度梯度（或 Sobolev）和微湍流近似进行比较。与周的言论相反，我们没有发现线宽的高估，尽管动力学演化类似于拉尔森-彭斯顿解而不是膨胀波解。此外，坠落运动产生线谱中延伸至 v = ±2 km s-1 的翅膀，这与以前的作品形成鲜明对比，之前的作品无法通过坠落模型产生翅膀。这些结果意味着简化的瀑布模型，例如先前作者采用的等温相似解，并不总是适合线谱的详细建模。
A double-peaked profile with a stronger blue peak in a molecular line spectrum is considered strong evidence for the infall motion in the gas envelope surrounding a protostar. Some past studies performed model calculations for reproducing observed spectral profiles using simplified dynamical models such as isothermal similarity solutions. However, validity of the similarity solutions for spectral line synthesis should be examined in comparison with more realistic dynamical models. In this paper we carry out theoretical modeling of molecular line spectra, adopting a spherically symmetric radiation hydrodynamical model for protostar formation taken from a recent work by the authors. This study concentrates on how infall motions could account for the asymmetric line profiles observed toward protostellar sources. We do not explicitly consider the effects of rotation and outflows on the generation of line profiles. In our numerical code for the non-LTE line transfer, the level populations are fully consistent with the radiation field under an arbitrary physical structure in spherical symmetry, and hence, reliable spectral synthesis has been enabled and compared to the LTE, large velocity gradient (or Sobolev), and microturbulence approximations. Contrary to the remarks by Zhou, we do not find an overestimation of line widths, although the dynamical evolution resembles the Larson-Penston solution rather than the expansion-wave solution. Furthermore, the infall motion produces wings extending to v = ±2 km s-1 in line spectra, in contrast to previous works where wings could not be produced by infall models. These results imply that simplified infall models, such as the isothermal similarity solutions adopted by previous authors, are not always suitable to the detailed modeling of line spectra.