标题： 反射星云NGC7023中冷却线的空间变化 显示英文标题

标题： The Spatial Variation of the Cooling Lines in the Reflection Nebula NGC7023

摘要： 上下文：反射星云NGC 7023中的西北光致离解区（PDR）表现出复杂的结构。在云团边缘的丝状凝聚可以通过主要冷却线的发射进行追踪，这为研究这些区域的形态和能量学之间的联系提供了绝佳的机会。 目标：我们研究[ C II ]（158微米）和[ O I ]（63和145微米）远红外精细结构线的空间变化。这些线追踪PDR中的局部气体条件。 方法：我们使用赫歇尔/PACS仪器的观测数据来绘制这些精细结构线的空间分布。观测区域覆盖一个约110" x 110"的正方形区域，角分辨率从4"到11"不等。我们将这种发射与地面观测和斯皮策观测的H2线、赫歇尔/SPIRE观测的CO线以及斯皮策/IRAC 3.6微米图像进行了比较，这些图像追踪多环芳烃的发射。 结果：[ C II ]（158微米）和[ O I ]（63和145微米）线来源于PDR所在的温暖云表面，气体温暖，使该区域冷却。我们发现尽管在观测区域内[ O I ]63微米对冷却预算的相对贡献占主导地位（>30%），但在PDR中H2的贡献显著（35%），并且在PDR外部[ C II ]158微米的贡献也达到30%。其他物种对冷却的贡献很少（[ O I ]145微米为9%，CO为4%）。[ O I ]图将这些凝聚体解析为两个结构，并显示[ O I ]的峰值略微偏离分子H2的发射。这些结构的尺寸约为8"（0.015 pc），在表面覆盖约9%的PDR发射。最后，我们没有检测到[ N II ]122微米的发射，这表明该空腔主要由非电离气体填充。 显示英文摘要

摘要： Context: The north-west photo-dissociation region (PDR) in the reflection nebula NGC 7023 displays a complex structure. Filament-like condensations at the edge of the cloud can be traced via the emission of the main cooling lines, offering a great opportunity to study the link between the morphology and energetics of these regions. Aims: We study the spatial variation of the far-infrared fine-structure lines of [C II] (158 um) and [O I] (63 and 145 um). These lines trace the local gas conditions across the PDR. Methods: We used observations from the Herschel/PACS instrument to map the spatial distribution of these fine-structure lines. The observed region covers a square area of about 110" x 110" with an angular resolution that varies from 4" to 11". We compared this emission with ground-based and Spitzer observations of H2 lines, Herschel/SPIRE observations of CO lines, and Spitzer/IRAC 3.6 um images that trace the emission of polycyclic aromatic hydrocarbons. Results: The [C II] (158 um) and [O I] (63 and 145 um) lines arise from the warm cloud surface where the PDR is located and the gas is warm, cooling the region. We find that although the relative contribution to the cooling budget over the observed region is dominated by [O I]63 um (>30%), H2 contributes significantly in the PDR (35%), as does [C II]158 um outside the PDR (30%). Other species contribute little to the cooling ([O I]145 um 9%, and CO 4%). The [O I] maps resolve these condensations into two structures and show that the peak of [O I] is slightly displaced from the molecular H2 emission. The size of these structures is about 8" (0.015 pc) and in surface cover about 9% of the PDR emission. Finally, we did not detect emission from [N II]122 um, suggesting that the cavity is mostly filled with non-ionised gas.