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arXiv 1801.01643astro-ph.GA
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船底座星云中Trumpler 14的PDR的约束物理条件

Constraining physical conditions for the PDR of Trumpler 14 in the Carina Nebula

Ronin Wu, Emeric Bron, Takashi Onaka, Franck Le Petit, Frederic Galliano, David Languignon, Tomohiko Nakamura, Yoko Okada

备注：
Accepted for publication by A&A, comments are welcome
发表信息：
A&A 618, A53 (2018)
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摘要：

我们研究了船底座星云Trumpler 14年轻星团附近CO气体的物理条件。本工作中的观测是用赫歇尔空间天文台上的光谱和光度成像接收器（SPIRE）的傅里叶变换光谱仪（FTS）进行的。我们的视野覆盖了大约$1\,\mathrm{Myr}$前由Trumpler 14雕刻的腔的边缘，并标记了从HII区域到光解离区域的过渡。利用最先进的Meudon PDR程序，我们成功地从观测到的CO谱线能量分布~（SLEDs）中导出了包括热压力（$P$）和辐射场标度因子（$G_{\mathrm{UV}}$）在内的物理条件。推导出的$G_{\mathrm{UV}}$值一般表现出良好的协议与附近的OB-星所产生的紫外辐射场，从而确认所观察到的CO排放的主要激发源是由大质量恒星提供的紫外光子。推导出的热压力介于$0.5-3\,\times\,10^{8}\,\mathrm{K\,cm^{-3}}$和Trumpler 14对面的Car I-E区域电离锋的最高值之间，暗示云结构与猎户座酒吧最近的观测结果相似。比较推导的热压力与辐射场，我们报告的第一个观测推导和空间分辨的$P \sim 2\times10^4\,G_{\mathrm{UV}}$关系。由于建模结果与观测到的$^{13}\mathrm{CO}$、[OI] $63\,\mathrm{μm}$和[CII] $158\,\mathrm{μm}$强度的直接比较并不简单，因此我们敦促读者在使用$^{12}\mathrm{CO}$、$^{13}\mathrm{CO}$、[CI]、[OI] $63\,\mathrm{μm}$和[CII] $158\,\mathrm{μm}$观测结果的组合来约束PDR的物理条件时要谨慎。

英文摘要：

We investigate the physical conditions of the CO gas near the young star cluster, Trumpler 14 of the Carina Nebula. The observations presented in this work are taken with the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) onboard the Herschel Space Observatory. Our field of view covers the edge of a cavity carved by Trumpler 14 about $1\,\mathrm{Myr}$ ago and marks the transition from HII regions to photo-dissociation regions. With the state-of-the-art Meudon PDR code, we successfully derive the physical conditions, which include the thermal pressure ($P$) and the scaling factor of radiation fields ($G_{\mathrm{UV}}$), from the observed CO spectral line energy distributions~(SLEDs) in the observed region. The derived $G_{\mathrm{UV}}$ values generally show an excellent agreement with the UV radiation fields created by nearby OB-stars and thus confirm that the main excitation source of the observed CO emission are the UV-photons provided by the massive stars. The derived thermal pressure is between $0.5-3\,\times\,10^{8}\,\mathrm{K\,cm^{-3}}$ with the highest values found along the ionization front in Car I-E region facing Trumpler 14, hinting that the cloud structure is similar to the recent observations of the Orion Bar. Comparing the derived thermal pressure with the radiation fields, we report the first observationally-derived and spatially-resolved $P \sim 2\times10^4\,G_{\mathrm{UV}}$ relationship. As direct comparisons of the modeling results to the observed $^{13}\mathrm{CO}$, [OI] $63\,\mathrm{μm}$, and [CII] $158\,\mathrm{μm}$ intensities are not straightforward, we urge the readers to be cautious when constraining the physical conditions of PDRs with combinations of $^{12}\mathrm{CO}$, $^{13}\mathrm{CO}$, [CI], [OI] $63\,\mathrm{μm}$, and [CII] $158\,\mathrm{μm}$ observations.

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