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arXiv 1503.01225astro-ph.GA
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沿紫外加热流出腔壁的暖CO气体:嵌入YSO的Herschel/PACS CO谱的可能解释

The warm CO gas along the UV-heated outflow cavity walls: a possible interpretation for the Herschel/PACS CO spectra of embedded YSOs

Seokho Lee, Jeong-Eun Lee, Edwin A. Bergin

摘要:

由\textit{Herschel} /PACS对嵌入的年轻恒星天体(YSO)的观测所探测到的$J$中期($J$ = 14 - 13至$J$ = 24- 23)CO辐射的一小部分被归因于紫外加热的流出腔壁。我们应用我们新发展的光子主导区(PDR)和非局域热平衡线辐射传输一般网格(RIG)的自洽模型,对27个低质量YSO和一个中等质量YSO(NGC 7129-FIRS 2)的\textit{Herschel} FIR观测进行了计算。当去除热分量的贡献(由$J> 24$的跃迁追踪)时,暖分量的转动温度几乎与$\sim250$ K恒定。这可以通过流出空腔壁($n \geq 10^6\, \mathrm{cm}^{-3}$、$\log G_{0}/n \geq-4.5$、$\mathrm{log} G_0\ge 3$、$T_{\rm gas} \ge 300 $ K和X(CO)$ \ge 10^{-5}$)来再现,所述流出空腔壁由黑体温度为15,000 K或10,000 K的UV辐射场加热。然而,需要一个与内部PDR相结合的冲击模型来确定PDR相对于冲击对中间$J$ CO排放的定量贡献。

英文摘要:

A fraction of the mid-$J$ ($J$= 14--13 to $J$= 24--23) CO emission detected by the \textit{Herschel}/PACS observations of embedded young stellar objects (YSOs) has been attributed to the UV-heated outflow cavity walls. We have applied our newly developed self-consistent models of Photon-Dominated Region (PDR) and non-local thermal equilibrium line Radiative transfer In general Grid (RIG) to the \textit{Herschel} FIR observations of 27 low mass YSOs and one intermediate mass YSO, NGC7129-FIRS2. When the contribution of the hot component (traced by transitions of $J> 24$) is removed, the rotational temperature of the warm component is nearly constant with $\sim250$ K. This can be reproduced by the outflow cavity wall ($n \geq 10^6\, \mathrm{cm}^{-3}$, $\log G_{0}/n \geq-4.5$, $\mathrm{log} G_0\ge 3$, $T_{\rm gas} \ge 300 $K, and X(CO)$ \ge 10^{-5}$) heated by a UV radiation field with a black body temperature of 15,000 K or 10,000 K. However, a shock model combined with an internal PDR will be required to determine the quantitative contribution of a PDR relative to a shock to the mid-$J$ CO emission.

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