C冲击的参数化。颗粒溅射的演变
Parametrization of C-shocks. Evolution of the Sputtering of Grains
摘要：
内容：对L1448-mm流出的年轻冲击的窄SiO线的检测已被解释为C-冲击的磁性前兆的签名。与环境气体中的低SiO丰度（<10 E-12）相比，在几乎环境速度下的窄SiO排放显示出10 E-11的SiO丰度增强。这种增强被认为是由C-冲击第一阶段的颗粒地幔溅射产生的。然而，溅射颗粒的建模通常平均的SiO丰度的耗散区的C-冲击，这不能解释最近的观察。目的：模拟冲击波在环境气体中传播时颗粒溅射产生的SiO、CH 3OH和H2O气相丰度的演化。方法：我们提出了一个参数模型来描述作为时间的函数的物理结构的C-冲击。使用已知的溅射产率的水地幔（与次要成分，如硅和CH 3OH）和橄榄石的核心与H2，He，C，O，Si，Fe和CO的碰撞，我们遵循的演变的硅，CH 3OH和H2O的丰度喷出的晶粒。结果：这些丰度的演变表明，CO似乎是最有效的溅射剂在低速冲击。与其他模型相比，CO使硅从晶粒地幔溅射的速度阈值降低了5-10 km s-1。在低速激波的早期阶段，CO的溅射可以产生10 E-11的SiO丰度，这与在L1448-mm的磁性前兆中观察到的一致.我们的模型还满意地再现了在同一区域内两个Vs=30和60 kms-1的激波共存时，在该外流中观察到的SiO、CH_3OH和H_2O的逐渐增强.
英文摘要：
Context: The detection of narrow SiO lines toward the young shocks of the L1448-mm outflow has been interpreted as a signature of the magnetic precursor of C-shocks. In contrast with the low SiO abundances (<10E-12) in the ambient gas, the narrow SiO emission at almost ambient velocities reveals enhanced SiO abundances of 10E-11. This enhancement has been proposed to be produced by the sputtering of the grain mantles at the first stages of C-shocks. However, modelling of the sputtering of grains has usually averaged the SiO abundances over the dissipation region of C-shocks, which cannot explain the recent observations. Aims: To model the evolution of the gas phase abundances of SiO, CH3OH and H2O, produced by the sputtering of grains as the shock propagates through the ambient gas. Methods: We propose a parametric model to describe the physical structure of C-shocks as a function of time. Using the known sputtering yields for water mantles (with minor constituents like silicon and CH3OH) and olivine cores by collisions with H2, He, C, O, Si, Fe and CO, we follow the evolution of the abundances of silicon, CH3OH and H2O ejected from grains. Results: The evolution of these abundances shows that CO seems to be the most efficient sputtering agent in low velocity shocks. The velocity threshold for the sputtering of silicon from the grain mantles is reduced by 5-10 km s-1 by CO compared to other models. The sputtering by CO can generate SiO abundances of 10E-11 at the early stages of low velocity shocks, consistent with those observed in the magnetic precursor of L1448-mm. Our model also satisfactorily reproduce the progressive enhancement of SiO, CH3OH and H2O observed in this outflow by the coexistence of two shocks with vs=30 and 60kms-1 within the same region.
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