蛇夫座ρ中S1周围的C ^+分布
C^+ distribution around S1 in rho Ophiuchi
摘要：
我们分析了[C II] 158微米的地图获得的L2大接收器SOFIA的发射/反射星云照亮的早期B星S1在rho-OphA云核心。这一数据集得到了CO（3 - 2）、13CO（3 - 2）和C18O（3 - 2）地图的补充，这些地图是作为JCMT古尔德带巡天的一部分观测到的，还有存档的HCO ^+（4 - 3）JCMT数据，以及Herschel/PACS的[O I] 63和145微米成像。[C II]发射完全由S1周围星云的强PDR发射控制，该星云扩展到S1以西和以南的致密Oph A分子云。的[C II]发射显着蓝移相对于CO光谱，也相对于系统的速度，特别是在西北部的星云。[C II]线在S1星云中心较宽，在PDR壳层较窄。[C II]线在S1 PDR中的扩展区域上具有强烈的自吸收。根据[13 C II] F = 2 - 1超精细分量的强度，[C II]在星云的大部分区域都有相当厚的光学厚度。CO和~（13）CO（3 - 2）光谱具有较强的自吸收，而C_（18）O（3 - 2）光谱为单峰，中心位于自吸收的中间。我们已经使用了一个简单的两层LTE模型来表征背景和前景云贡献的[C II]排放。从这个分析中，我们估计由于前景云的消光约为9.9等，这略低于对S1的估计。由于PDR中的一些热气体没有被低J CO排放追踪，因此该结果似乎是相当合理的。使用平面平行PDR模型，根据观测到的[OI（145）]/[C II]亮度比和3100 - 5000 G0的FUV强度估计值，可以得出[C II]发射气体的密度约为3 - 4x10^3 cm ^-3。
英文摘要：
We analyze a [C II] 158 micron map obtained with the L2 GREAT receiver on SOFIA of the emission/reflection nebula illuminated by the early B star S1 in the rho-OphA cloud core. This data set has been complemented with maps of CO(3-2), 13CO(3-2) and C18O(3-2), observed as a part of the JCMT Gould Belt Survey, with archival HCO^+(4-3) JCMT data, as well as with [O I] 63 and 145 micron imaging with Herschel/PACS. The [C II] emission is completely dominated by the strong PDR emission from the nebula surrounding S1 expanding into the dense Oph A molecular cloud west and south of S1. The [C II] emission is significantly blue shifted relative to the CO spectra and also relative to the systemic velocity, particularly in the northwestern part of the nebula. The [C II] lines are broader towards the center of the S1 nebula and narrower towards the PDR shell. The [C II] lines are strongly self-absorbed over an extended region in the S1 PDR. Based on the strength of the [13C II] F = 2-1 hyperfine component, [C II] is significantly optically thick over most of the nebula. CO and 13CO(3-2) spectra are strongly self-absorbed, while C18O(3-2) is single peaked and centered in the middle of the self-absorption. We have used a simple two-layer LTE model to characterize the background and foreground cloud contributing to the [C II] emission. From this analysis we estimate the extinction due to the foreground cloud to be ~9.9 mag, which is slightly less than the reddening estimated towards S1. Since some of the hot gas in the PDR is not traced by low J CO emission, this result appears quite plausible. Using a plane parallel PDR model with the observed [OI(145)]/[C II] brightness ratio and an estimated FUV intensity of 3100-5000 G0 suggests that the density of the [C II] emitting gas is ~3-4x10^3 cm^-3.
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