AI 中文总结
本文通过热化学模型研究原行星盘阶段铵盐的形成，发现其在盘内中平面高效形成，宇宙射线驱动效应会增强r≈30 au内的铵盐形成，且改变CO与N₂雪线位置。
AI 中文摘要
铵盐可能是太阳系原始天体中挥发性物质的重要储库，但恒星形成过程中这些盐类如何以及何时形成的问题仍未明确。本文采用热化学模型研究原行星盘阶段铵盐的形成，结果显示铵盐在盘内中平面（即r≲50 au）的彗星形成区域内高效形成；模型预测，演化10 Myr后，该区域尘埃表面几乎所有可用氮都以盐的形式存在（主要是氰酸铵），硫则几乎全部以硫氢化铵的形式存在于盘内中平面。研究还发现，在r≈30 au以内，宇宙射线驱动的汇效应会增强铵盐的形成，该效应在≳1 Myr的时间尺度上逐步将气相CO转化为二氧化碳、气相N₂转化为盐并沉积在尘埃表面，这会影响CO和N₂径向雪线的位置，两者都会随时间向恒星方向移动。
英文摘要
Ammonium salts may represent an important reservoir of volatile species in Solar system primitive bodies, but the question of how and when these salts can form during the star formation process remains unknown. In this paper, we use thermo-chemical models to study the formation of ammonium salts during the protoplanetary disk stage. We show that ammonium salts form efficiently in the inner disk midplane (i.e. $r \lesssim 50 $ au), inside the comet forming region. In this region, our model predicts that almost all the available nitrogen is in the form of salts (i.e. mainly in ammonium cyanate) at the surface of grains after evolving for 10 Myrs. For sulfur, we show that almost all the available S is in the form of ammonium hydrosulfide in the inner disk midplane. We show that inside $r\sim 30$ au, ammonium salt formation is enhanced by a cosmic-ray-driven sink effect that progressively converts gas-phase CO and N$_2$ into carbon dioxide and salts, respectively, at the surface of grains on a timescale $\gtrsim 1$ Myr. This impacts the location of the CO and N$_2$ radial snowlines which both shift closer to the star as a function of time.
Comments12 pages
