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首页> 外文期刊>The Astrophysical journal >INFRARED SPACE OBSERVATORY LONG WAVELENGTH SPECTROMETER OBSERVATIONS OF C+ AND O~0 LINES IN ABSORPTION TOWARD SAGITTARIUS B2
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INFRARED SPACE OBSERVATORY LONG WAVELENGTH SPECTROMETER OBSERVATIONS OF C+ AND O~0 LINES IN ABSORPTION TOWARD SAGITTARIUS B2

机译：C +和O〜0线对射孢菌B2的红外空间观察长波谱仪观察。

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摘要

High spectral resolution Fabry-Perot observations of the [O Ⅰ] 63.2 and 145.5 μm and [C Ⅱ] 157.7 μm fine-structure lines are presented for the center of the Sagittarius B2 complex (Sgr B2). The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). Both the [O Ⅰ] 63.2 μm and the [C Ⅱ] 157.7μm lines are detected in absorption. The upper state level of atomic oxygen at 145.5 μm is in emission. Whereas the [O Ⅰ] 63.2 μm line is seen in absorption over the entire wavelength range -200 to 100 km s~(-1), the [C Ⅱ] 157.7μm line displays a more complex profile: absorption occurs at velocities less than 20 km s~(-1), and emission comes from the Sgr B2 complex at velocities greater than 20 km s~(-1). Using observations of the CO isotopes and of the H Ⅰ lines, absorption components can be associated with many clouds along the Sgr B2 line of sight. From these data, we were able to disentangle three different layers that contain atomic oxygen. These layers, as predicted by photodissociation region models, are characterized by different forms of carbon in the gas phase, i.e., the C~+ external layer, the C~+ to C~0 transition, and the CO internal layer. We derive lower limits for the column densities of atomic carbon and oxygen of the order of ～10~(18) cm~(-2) and 3 x 10~(19) cm~(-2), respectively. An O~0/CO ratio of around 2.5 is computed in the internal cores of the clouds lying along the line of sight, which means that ～70% of gaseous oxygen is in the atomic form and not locked into CO. The fact that the [C Ⅱ] 157.7μm line is detected in absorption implies that the main cooling line of the interstellar medium can be optically thick, especially in the direction of large star-forming complexes or in the nuclei of galaxies. This could partially account for the deficiency in the [C Ⅱ] 157.7 μm line that recently has been found toward infrared-bright galaxies in ISO data.
机译：在人马座B2配合物（Sgr B2）的中心，高光谱分辨率的[OⅠ] 63.2和145.5μm和[CⅡ] 157.7μm精细结构线观察到了。数据是通过红外空间天文台（ISO）上的长波光谱仪获得的。吸收中同时检测到[OⅠ] 63.2μm和[CⅡ]157.7μm谱线。原子氧的最高态水平为145.5μm。 [OⅠ] 63.2μm谱线在-200至100 km s〜（-1）的整个波长范围内吸收，而[CⅡ]157.7μm谱线表现出更复杂的分布：吸收发生在速度小于20 km s〜（-1），并且来自Sgr B2络合物的排放速度大于20 km s〜（-1）。利用对CO同位素和HⅠ线的观察，吸收成分可以与沿Sgr B2视线的许多云有关。从这些数据中，我们能够解开包含原子氧的三个不同层。如通过光解离区域模型所预测的，这些层的特征在于气相中碳的不同形式，即，C〜+外层，C〜+至C〜0的转变以及CO内层。我们得出原子碳和氧的柱密度的下限分别为〜10〜（18）cm〜（-2）和3 x 10〜（19）cm〜（-2）。沿视线位于云的内部核心中的O〜0 / CO比约为2.5，这意味着约70％的气态氧是原子形式的而不是被锁定在CO中。 [CⅡ]157.7μm的吸收线表明，星际介质的主要冷却线可以是光学上较粗的，尤其是在大的恒星形成复合物的方向或星系的核中。这可以部分地解释最近在ISO数据中发现的[CⅡ] 157.7μm谱线中的缺陷，该缺陷指向红外明亮的星系。

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