arXiv 2107.033502021-07-07astro-ph.EP

动力盘模式中冰的继承

Ice inheritance in dynamical disk models

Jennifer Bergner, Fred Ciesla

备注：: Accepted to ApJ

摘要：

行星形成盘的组成是由从星际介质继承的物质和在盘形成和演化过程中再加工的物质的组合决定的。事实上，彗星和原始陨石表现出类似星际的同位素比例和/或挥发性成分，支持一些原始物质完整地融入太阳星云的冰冷微行星。到目前为止，挥发性星际物质在盘阶段的生存还没有使用现实的盘物理学建模。在这里，我们提出了一个建模框架，以跟踪在磁盘内进行运输过程的尘埃颗粒星际冰的破坏，特别侧重于解释的原始材料纳入冰冷的星子。我们发现很难通过彗星的局部聚集来解释遗传，因为冰的破坏对于内部几十个Au的小颗粒（<10 μ m）是迅速的。相反，一个合理的遗传途径是在更大的圆盘半径形成鹅卵石，然后向内漂移到彗星形成区，其中的冰大部分被保存下来。超过~100金的小颗粒可以经历百分之几十水平的冰光解，然而实际上很少有冰从颗粒中损失，这可能使其成为原位冰化学的一个强大的网站。我们的模型还表明，许多复杂的有机物种应生存通过磁盘完好无损。这就提出了一种可能性，即在星际介质中合成的有机物可以通过冰体撞击传递到类地行星，从而有可能参与生命化学的起源。

英文摘要：

The compositions of planet-forming disks are set by a combination of material inherited from the interstellar medium and material reprocessed during disk formation and evolution. Indeed, comets and primitive meteorites exhibit interstellar-like isotopic ratios and/or volatile compositions, supporting that some pristine material was incorporated intact into icy planetesimals in the Solar Nebula. To date, the survival of volatile interstellar material in the disk stage has not been modeled using realistic disk physics. Here, we present a modeling framework to track the destruction of interstellar ices on dust grains undergoing transport processes within a disk, with a particular focus on explaining the incorporation of pristine material into icy planetesimals. We find it is difficult to explain inheritance through the local assembly of comets, as ice destruction is rapid for small (<10um) grains in the inner few tens of au. Instead, a plausible pathway to inheritance is to form pebbles at larger disk radii, which then drift inwards to the comet-forming zone with their ices mostly preserved. Small grains beyond ~100 au can experience ice photodissociation at the tens of percent level, however little of the ice is actually lost from the grain, likely making this a robust site for in situ ice chemistry. Our models also indicate that many complex organic species should survive passage through the disk intact. This raises the possibility that organics synthesized in the interstellar medium can be delivered to terrestrial planets by icy body impact and thus potentially participate in origins of life chemistry.

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