Resetting chemical clocks of hot cores based on S-bearing molecules
Resetting chemical clocks of hot cores based on S-bearing molecules
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DOI：
10.1051/0004-6361:20047186
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发表时间：
2004-04
影响因子：
6.5
通讯作者：
V. Wakelam;P. Caselli;C. Ceccarelli;E. Herbst;A. Castets
中科院分区：
文献类型：
--
作者：
V. Wakelam;P. Caselli;C. Ceccarelli;E. Herbst;A. Castets
我们报告的硫化学的理论研究，适用于热的核心，其中S-轴承的分子比已被提出，并用作化学钟。在以前的模型中，我们遵循的S-轴承的分子组成后，注入到气相中的颗粒地幔成分。在这项研究中，我们开发了一个时间依赖的化学模型与最新的反应速率系数。我们运行了几个案例，使用不同的现实化学成分的粮食地幔和气体前地幔蒸发。建模表明，S-轴承的分子比非常关键地取决于气体的温度和密度，原子氧的丰度，最重要的是，在气相中注入的硫的形式，这是非常鲜为人知的。因此，含硫分子的比率不能容易地用作化学钟。然而，对物理和化学结构的详细观测和仔细建模可以提供源年龄的提示，并限制地幔成分（即冷分子云中硫的形式），从而有助于解决硫耗尽之谜。我们详细分析了Orion和IRAS 16293-2422的情况。将现有的观测结果与我们的模型进行比较表明，从地幔释放的大部分硫主要以原子形式存在，或很快转化为原子形式。
We report a theoretical study of sulphur chemistry, as applied to hot cores, where S-bearing molecular ratios have been previously proposed and used as chemical clocks. As in previous models, we follow the S-bearing molecular composition after the injection of grain mantle components into the gas phase. For this study, we developed a time-dependent chemical model with up-to-date reaction rate coefficients. We ran several cases, using different realistic chemical compositions for the grain mantles and for the gas prior to mantle evaporation. The modeling shows that S-bearing molecular ratios depend very critically on the gas temperature and density, the abundance of atomic oxygen, and, most importantly, on the form of sulphur injected in the gas phase, which is very poorly known. Consequently, ratios of S-bearing molecules cannot be easily used as chemical clocks. However, detailed observations and careful modeling of both physical and chemical structure can give hints on the source age and constrain the mantle composition (i.e. the form of sulphur in cold molecular clouds) and, thus, help to solve the mystery of the sulphur depletion. We analyse in detail the cases of Orion and IRAS 16293-2422. The comparison of the available observations with our model suggests that the majority of sulphur released from the mantles is mainly in, or soon converted into, atomic form.