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arXiv 1811.03488astro-ph.GAastro-ph.EP
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星际冰上物种扩散率不确定性的统计研究及其对化学模式预测的影响

Statistical study of uncertainties in the diffusion rate of species on interstellar ice and its impact on chemical model predictions

Wasim Iqbal, Valentine Wakelam, Pierre Gratier

备注：
accepted for publication in A&A,
发表信息：
A&A 620, A109 (2018)
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摘要：

背景：尘埃表面物质的扩散是确定星际冰化学成分的关键过程。在尘埃表面，吸附的物种从一个势阱扩散到另一个势阱，并与其他吸附的反应物反应，形成简单和复杂的分子。目的：通过考虑吸附态扩散能的不确定性，我们研究了化学程序对模拟物种丰度的影响。我们的目标是通过识别表面物种，因为它们的扩散能的不确定性，导致一个更大的误差，以限制化学代码计算的丰度的不确定性。方法：我们运行各种情况下，在每种情况下，2000至10000模拟和不同的扩散能量的一些或所有表面物种随机。我们计算了皮尔逊相关系数之间的丰度和吸附物种的结合能的扩散比。我们确定了在冰和气相丰度中引入最大不确定性的物种。对于这些物种，我们运行了三组，每组2000次模拟，以量化它们引入的不确定性。结果如下：我们目前的各种分子在气相中的丰度，也在模拟过程中的不同时间间隔的灰尘表面。我们表明，哪些物种产生了很大的不确定性的丰度。我们根据物种在化学网络中传播不确定性的重要性将其分为不同的组。结论：我们发现，CO，H $_2$，O，N和CH $_3$是关键物种的丰度的不确定性，而CH $_2$，HCO，S和O $_2$来其次，其次是NO，HS和CH。我们还表明，通过限制这些物种的结合能的扩散比的不确定性，我们可以消除几乎所有的物种的气相丰度的不确定性。

英文摘要：

Context: Diffusion of species on the dust surface is a key process for determining the chemical composition of interstellar ices. On the dust surface, adsorbed species diffuse from one potential well to another and react with other adsorbed reactants, resulting in the formation of simple and complex molecules. Aims: We study the impact on the abundances of the species simulated by the chemical codes by considering the uncertainties in the diffusion energy of adsorbed species. We aim to limit the uncertainties in the abundances as calculated by chemical codes by identifying the surface species that result in a larger error because of the uncertainties in their diffusion energy. Methods: We ran various cases with 2000 to 10000 simulations in each case and varied the diffusion energies of some or all surface species randomly. We calculated Pearson correlation coefficients between the abundances and the ratio of diffusion to binding energy of adsorbed species. We identified the species that introduce maximum uncertainty in the ice and gas-phase abundances. With these species we ran three sets, with 2000 simulations in each, to quantify the uncertainties they introduce. Results: We present the abundances of various molecules in the gas phase and also on the dust surface at different time intervals during the simulation. We show which species produce a large uncertainty in the abundances. We sorted species into different groups in accordance with their importance in propagating uncertainty in the chemical network. Conclusions: We show that CO, H$_2$, O, N, and CH$_3$ are the key species for uncertainties in the abundances, while CH$_2$, HCO, S and O$_2$ come next, followed by NO, HS, and CH. We also show that by limiting the uncertainties in the ratio of diffusion to binding energy of these species, we can eliminate the uncertainties in the gas-phase abundances of almost all the species.

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