论文标题
OH中红外排放作为h $ _2 $ o uv potodissociation的诊断。 ii。应用于星际PDR
OH mid-infrared emission as a diagnostic of H$_2$O UV photodissociation. II. Application to interstellar PDRs
论文作者
论文摘要
在114-144 nm UV范围内的水光解离量激发了OH，该旋转线在中红外波长下排放。这些线仅在几个原始星际磁盘和冲击中用spitzer检测到。先前的研究表明，它们是水光解离的独特诊断。由于其高灵敏度和角度分辨率，James Webb太空望远镜（JWST）能够在其他环境中检测到它们，例如星际照相隔离区域（PDRS）。为了预测OH的新兴频谱，我们使用Meudon PDR代码来计算PDR的热和化学结构。热压（$ p _ {\ rm th}/k $ = $ = $ n _ {\ rm h} t _ {\ rm k} $）和紫外线强度对集成强度以及与JWST的可检测性有关。 OH MID-IR排放预计将非常接近H $^0 $/H $ _2 $过渡，并且与该层中的水的柱密度成正比。由于水的中性气相形成需要相对较高的温度（$ t _ {\ rm k} \ gtrsim 300〜 $ k），因此所得的OH MID-IR线主要与该位置处的温度相关，因此在高压区域中更明亮。这意味着预计这些线只能在强烈辐照的PDR（$ G_0^{\ rm事件} $ $> $> $ 10 $^3 $）中具有高热压力（$ P _ {\ rm th}/k $ $ $ $ \ $ \ $ \ gtrsim $ 5 $ 5 $ \ times $ 5 $ \ times $ 10 $^7 $ k cm $ k cm $ cm $^} $ 3}。在后一种情况下，OH MID-IR线不太依赖于事件紫外线的强度。还研究了应有的PDR中的检测，例如猎户座棒。总而言之，JWST可观察到的OH MID-IR线是致密和强烈辐照的PDR的有前途的诊断。
Water photodissociation in the 114 - 144 nm UV range forms excited OH which emits at mid-infrared wavelengths via highly excited rotational lines. These lines have only been detected with Spitzer in several proto-planetary disks and shocks. Previous studies have shown they are a unique diagnostic for water photodissociation. Thanks to its high sensitivity and angular resolution, the James Webb Space Telescope (JWST) could be able to detect them in other environments such as interstellar Photo-Dissociation Regions (PDRs). In order to predict the emerging spectrum of OH, we use the Meudon PDR Code to compute the thermal and chemical structure of PDRs. The influence of thermal pressure ($P_{\rm th}/k$ = $n_{\rm H} T_{\rm K}$) and UV field strength on the integrated intensities, as well as their detectability with the JWST are studied in details. OH mid-IR emission is predicted to originate very close to the H$^0$/H$_2$ transition and is directly proportional to the column density of water photodissociated in that layer. Because neutral gas-phase formation of water requires relatively high temperatures ($T_{\rm K} \gtrsim 300~$K), the resulting OH mid-IR lines are primarily correlated with the temperature at this position, and are therefore brighter in regions with high pressure. This implies that these lines are predicted to be only detectable in strongly irradiated PDRs ($G_0^{\rm incident}$ $>$ 10$^3$) with high thermal pressure ($P_{\rm th}/k$ $\gtrsim$ 5$\times$10$^7$ K cm$^{-3}$). In the latter case, OH mid-IR lines are less dependent on the strength of the incident UV field. The detection in PDRs like the Orion bar, which should be possible, is also investigated. To conclude, OH mid-IR lines observable by JWST are a promising diagnostics for dense and strongly irradiated PDRs.
