Gas giant formation with small cores triggered by envelope pollution by icy planetesimals
Gas giant formation with small cores triggered by envelope pollution by icy planetesimals
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DOI：
10.1111/j.1365-2966.2011.19140.x
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发表时间：
2011-09-01
影响因子：
4.8
通讯作者：
Ikoma, M.
中科院分区：
文献类型：
--
作者：
Hori, Y.;Ikoma, M.
我们研究了冰冷的星子污染包膜如何影响气体巨星形成的临界核心质量和气体吸积的时间尺度。在核心吸积模型中，当核心达到临界核心质量时，会触发失控的气体吸积。以往关于核心吸积模型的所有研究都假定包层具有均匀的太阳成分。事实上，包层很可能被冰态星子的蒸发物质所污染，因为穿过包层的冰态星子会因强烈的烧蚀而经历质量损失，它们的大部分质量都沉积在深包层中。在本文中，我们已经证明，由于分子质量的增加和绝热温度梯度的降低，包络污染通常会降低临界核心质量并加速气体向原行星的吸积。广泛和高度污染的外壳允许较小的内核在磁盘耗散之前形成巨大的外壳。我们的研究结果表明，行星吸积过程中的包层污染有可能引发具有小核的气体巨星的形成。我们建议在讨论基于核心吸积模型的气体巨星形成时，有必要考虑冰冷的星子对包络层的污染。
We have investigated how envelope pollution by icy planetesimals affects the critical core mass for gas giant formation and the gas accretion time-scales. In the core-accretion model, runaway gas accretion is triggered after a core reaches a critical core mass. All the previous studies on the core-accretion model assumed that the envelope has the solar composition uniformly. In fact, the envelope is likely polluted by evaporated materials of icy planetesimals because icy planetesimals going through the envelope experience mass-loss via strong ablation and most of their masses are deposited in the deep envelope. In this paper, we have demonstrated that envelope pollution in general lowers the critical core masses and hastens gas accretion on to the protoplanet because of the increase in the molecular weight and reduction in the adiabatic temperature gradient. Widely and highly polluted envelopes allow smaller cores to form massive envelopes before disc dissipation. Our results suggest that envelope pollution in the course of planetary accretion has the potential to trigger gas giant formation with small cores. We propose that it is necessary to take into account envelope pollution by icy planetesimals when we discuss gas giant formation based on the core accretion model.