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arXiv 0804.2883astro-ph
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Orion KL的物理参数来自模拟其ISO高分辨率远红外CO线光谱

Physical parameters for Orion KL from modelling its ISO high resolution far-IR CO line spectrum

M. R. Lerate, J. Yates, S. Viti, M. J. Barlow, B. M. Swinyard, G. J. White, J. Cernicharo, J. R. Goicoechea

摘要:

作为猎户座KL地区第一次高分辨率远红外光谱调查的一部分(Leerate等人,2006年),我们观察到20条CO发射线,Jup=16至Jup=39(高于基态约752 K至4294 K的上能级)。观测是使用红外空间观测台(ISO)上的长波光谱仪以其高分辨率法布里-珀罗(FP)模式(约33公里/秒$^{-1}$)进行的。我们在这里提出了一个分析的最终校准CO数据,执行一个更复杂的建模技术比迄今为止,包括化学的详细分析,并讨论与以前的结果的相似性和差异。包括化学建模意味着原子和分子丰度的时间预测的化学。这提供了一个主要的区别与以往的研究中,化学丰度需要假设为初始条件。通过模拟KL区域不同已知组成部分的条件来研究该区域的化学:热核、高原和脊的化学模型与加速的λ迭代(ALI)辐射转移模型相结合,以预测线通量和剖面。我们的结论是,CO的18<Jup<25的跃迁主要来自一个直径为0.02 pc,密度为10 $^{7}$ cm $^{-3}$的热核,而不是像以前的研究所指出的那样来自平台。

英文摘要:

As part of the first high resolution far-IR spectral survey of the Orion KL region (Lerate et al. 2006), we observed 20 CO emission lines with Jup=16 to Jup=39 (upper levels from approx 752 K to 4294 K above the ground state). Observations were taken using the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO), in its high resolution Fabry-Perot (FP) mode (approx 33 km s$^{-1}$). We present here an analysis of the final calibrated CO data, performed with a more sophisticated modelling technique than hitherto, including a detailed analysis of the chemistry, and discuss similarities and differences with previous results. The inclusion of chemical modelling implies that atomic and molecular abundances are time-predicted by the chemistry. This provides one of the main differences with previous studies in which chemical abundances needed to be assumed as initial condition. The chemistry of the region is studied by simulating the conditions of the different known components of the KL region: chemical models for a hot core, a plateau and a ridge are coupled with an accelerated Lambda-iteration (ALI)radiative transfer model to predict line fluxes and profiles. We conclude that the CO transitions with 18<Jup<25 mainly arise from a hot core of diameter 0.02 pc and a density of 10$^{7}$ cm$^{-3}$ rather from the plateau as previous studies had indicated.

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