Abundant gas-phase H2O in absorption toward massive protostars ?
Abundant gas-phase H2O in absorption toward massive protostars ?
复制标题
大量的气相 H2O 被大质量原恒星吸收？
DOI：
10.1051/0004-6361:20030364
复制
发表时间：
2003
影响因子：
6.5
通讯作者：
E. V. van Dishoeck
中科院分区：
文献类型：
--
作者：
A. Boonman;E. V. van Dishoeck
利用红外空间天文台（ISO）上的短波光谱仪获得了12颗深埋大质量原恒星的6 μ m附近气相H2O的红外光谱。在7个源的方向上检测到了转振带，激发温度表明起源于T_{{\rm ex}}\ga 250$ K的暖气体。典型的推导气相H 2 O丰度为~$5\times10^{-6}{-}6\times10^{-5}$，丰度随暖气体温度的升高而增加。推断的气/固比显示出类似的趋势与温度，并建议，颗粒地幔蒸发是很重要的。增加的气/固比与增加的温度的其他指标相关。如果较高的温度是由于一个较大的比率源光度包封质量，这使得气相水一个很好的演化示踪剂。与化学模型的比较表明，三种不同的化学过程，冰蒸发，高温化学，冲击，可以重现高推断气相H2O丰度。在即将发表的论文中，这些过程中的每一个都进行了更详细的研究，并与ISO和亚毫米波天文卫星（SWAS）上的长波光谱仪的数据进行了比较。与现有的SWAS数据的比较表明，在H2 O丰度的跳跃是存在的，所观察到的振转带痕迹主要是温暖的内部信封。
We present infrared spectra of gas-phase H 2 O around 6 μ m toward 12 deeply embedded massive protostars obtained with the Short Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The $\nu_2$ ro-vibrational band has been detected toward 7 of the sources and the excitation temperatures indicate an origin in the warm gas at $T_{{\rm ex}}\ga 250$ K. Typical derived gas-phase H 2 O abundances are ~$5\times10^{-6}{-}6\times10^{-5}$, with the abundances increasing with the temperature of the warm gas. The inferred gas/solid ratios show a similar trend with temperature and suggest that grain-mantle evaporation is important. The increasing gas/solid ratio correlates with other indicators of increased temperatures. If the higher temperatures are due to a larger ratio of source luminosity to envelope mass, this makes gas-phase H 2 O a good evolutionary tracer. Comparison with chemical models shows that three different chemical processes, ice evaporation, high- T chemistry, and shocks, can reproduce the high inferred gas-phase H 2 O abundances. In a forthcoming paper each of these processes are investigated in more detail in comparison with data from the Long Wavelength Spectrometer on board ISO and the Submillimeter Wave Astronomy Satellite (SWAS). Comparison with existing SWAS data indicates that a jump in the H 2 O abundance is present and that the observed $\nu_2$ ro-vibrational band traces primarily the warm inner envelope.