水雪线外阴影原太阳盘中面的分子组成
The Molecular Composition of Shadowed Protosolar Disk Midplanes beyond the Water Snowline
摘要：
磁盘中板温度可能会受到灰尘陷阱/环的影响。在水雪线之外的灰尘耗尽将投下阴影。在这项研究中，我们采用了一个详细的气体颗粒化学反应网络，并调查径向气体和冰的丰度分布的主要碳，氧，氮轴承分子在磁盘的阴影结构超出水雪线周围的原太阳系恒星。在阴影盘中，预计$3-8$ au附近的尘埃颗粒具有大约$5-10$倍的有机分子冰，如H $_{2}$ CO，CH $_{3}$ OH和NH $_{2}$ CHO，饱和烃冰如CH $_{4}$和C $_{2}$ H $_{6}$，除了H $_{2}$ O，CO，CO $_{2}$，NH $_{3}$，N $_{2}$和HCN冰，与非阴影磁盘中的那些相比。在阴影区，我们发现氢化（特别是CO冰）是复杂有机分子的主要形成机制。气相N/O比的空间变化比气相C/O比大得多，因此，N/O比是一个有用的示踪剂的阴影区。N $_{2}$ H $^{+}$谱线发射是阴影区的潜在示踪剂。我们的结论是，阴影区允许的关键挥发物到尘埃颗粒的再冷凝，提供了一个区域的化学富集的冰，这是更接近恒星比在一个非阴影磁盘，并可能在一定程度上解释O $_{2}$冰的尘埃颗粒，形成彗星67 P/丘留莫夫-格拉西缅科的陷阱。我们讨论的是，如果形成在一个阴影盘，木星不需要有迁移的距离很远。
英文摘要：
The disk midplane temperature is potentially affected by the dust traps/rings. The dust depletion beyond the water snowline will cast a shadow. In this study, we adopt a detailed gas-grain chemical reaction network, and investigate the radial gas and ice abundance distributions of dominant carbon-, oxygen-, and nitrogen-bearing molecules in disks with shadow structures beyond the water snowline around a protosolar-like star. In shadowed disks, the dust grains at around $3-8$ au are predicted to have more than around $5-10$ times amounts of ices of organic molecules such as H$_{2}$CO, CH$_{3}$OH, and NH$_{2}$CHO, saturated hydrocarbon ices such as CH$_{4}$ and C$_{2}$H$_{6}$, in addition to H$_{2}$O, CO, CO$_{2}$, NH$_{3}$, N$_{2}$, and HCN ices, compared with those in non-shadowed disks. In the shadowed regions, we find that hydrogenation (especially of CO ice) is the dominant formation mechanism of complex organic molecules. The gas-phase N/O ratios show much larger spatial variations than the gas-phase C/O ratios, thus the N/O ratio is predicted to be a useful tracer of the shadowed region. N$_{2}$H$^{+}$ line emission is a potential tracer of the shadowed region. We conclude that a shadowed region allows the recondensation of key volatiles onto dust grains, provides a region of chemical enrichment of ices that is much closer to the star than within a non-shadowed disk, and may explain to some degree the trapping of O$_{2}$ ice in dust grains that formed comet 67P/Churyumov-Gerasimenko. We discuss that, if formed in a shadowed disk, Jupiter does not need to have migrated vast distances.
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