The origin of H2O+ in dense clouds

We try to resolve the chemical evolution of oxygen hydrides in <br>radiatively heated dense clouds. This involves in particular H2O+ <br>and chemically related species, which are formed by gasphase <br>reactions initiated by cosmic ray ionization in diffuse clouds, but <br>may be predominantly produced by the evaporation of icy grain <br>mantles and the subsequent ionization of water by UV radiation <br>in heated dense clouds. We will investigate the full chain of species <br>OH+, H2O+, H3O+, OH, and H2O, connected by gas phase <br>reactions, to quantify the contribution of ice evaporation in dense <br>clouds.<br><br>We propose to observe these species in the dense layers known to<br>exist in two massive starforming regions, DR21(C), where <br>indications of H2O+ from hot gas were already found and where <br>the hot layer is affected both by UV radiation and a strong shock <br>from a bipolar outflow, and Mon R2, a PDR with similar parameters <br>but no indications of shock processing of the hot layer.<br><br>Differences between the results from the two sources will provide <br>an estimate for the impact of shocks on the H2O+ production. By <br>comparing the observed abundances of OH+, H2O+, H3O+, OH, <br>and H2O with steadystate PDR models, we will be able to <br>quantify the amount of water that is fed into the gas phase by the <br>evaporation or photodesorption of ice mantles from dust grains. [truncated!, Please see actual data for full text] [truncated!, Please see actual data for full text]

本研究旨在解析辐射加热致密云中氧氢化合物的化学演化过程。特别是涉及水合氢离子（H2O+）及其化学相关物种，这些物种由扩散云中的宇宙射线电离引发的气相反应形成，但可能主要来源于冰质颗粒外壳的蒸发以及随后在加热致密云中由紫外辐射引起的水的电离。我们将研究由气相反应连接的物种全链，包括OH+、H2O+、H3O+、OH和H2O，以量化致密云中冰蒸发对水含量的贡献。我们计划在两个已知存在致密层的巨型恒星形成区域DR21(C)和Mon R2进行观测，其中DR21(C)区域已发现H2O+的热气体迹象，且该区域的热层同时受到紫外辐射和来自双极流的强烈冲击的影响，而Mon R2则是一个具有相似参数的PDR区域，但其热层未发现冲击处理迹象。两种来源结果之间的差异将为冲击对H2O+生成的影响提供估算。通过将观测到的OH+、H2O+、H3O+、OH和H2O的丰度与稳态PDR模型进行比较，我们将能够量化由尘埃颗粒冰外壳的蒸发或光解所输送到气相中的水量。[文本截断，请参阅实际数据以获取全文][文本截断，请参阅实际数据以获取全文]