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.
The 12C/13C Isotopic Ratio in Photodissociated Gas in M42
我们在猎户座光解离区θ 1C附近同时观测到12 C II的158微米2 P3/2- 2 P12精细结构线和13 C II中该跃迁的F=2-1和F=1-0超精细分量。线轮廓完全解决了使用外差光谱仪与0.5公里/秒的分辨率。这些谱线的相对强度给出了12 C/13 C同位素比R=58(+6,-5),最可能的12 C II峰光学深度τ =1.3。tau(12 C II)在1.0和1.4之间的约束范围对应于12 C/13 C在52和61之间的范围。58的最可能值与从CO测量得到的同位素比和银河中心距离之间的关系非常一致,但低于从CO数据得到的猎户座的具体值67(± 3)。一个低至43的同位素比,如前所述,根据当地星际介质的光吸收测量,被排除在约2西格玛水平的C II数据。
Extended Far-Infrared CO Emission in the Orion OMC-1 Core
我们报告敏感的远红外观测$^{12}$ CO纯转动过渡OMC-1核心的猎户座。这些谱线是用红外空间天文台(ISO)上的长波长分光仪(LWS)以光栅模式观测的,覆盖43-197 $μ$ m波长范围。已经在整个OMC-1核心中鉴定了从$J_{up}=14$直至$J_{up}=19$的转变,并且已经检测到朝向中心区域KL/IRc 2的直至$J_{up}= 43$的线。此外,我们已经采取了高质量的光谱中的法布里-珀罗模式的一些CO线。在KL/IRc 2中,用三温度模型描述平台和脊发射,令人满意地解释了这些线。在高$J$跃迁($J_{up} > 34$)中检测到的通量揭示了一种非常热和稠密的气体成分($T=1500-2500$ K; $\rm N(CO)$ =2 \times 10^{17} \cmmd $), probably originating from some of the embedded sources previously observed in the $ \rm H_2 $ near-infrared lines. At all other positions in the OMC-1 core, we estimate kinetic temperatures $ \geq 80$ K和高达150 K)的存在,这是由一个简单的大速度梯度模型得出的。