Constraining the initial planetary population in the gravitational instability model
Constraining the initial planetary population in the gravitational instability model
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DOI：
10.1093/mnras/stz2006
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发表时间：
2019-10-01
影响因子：
4.8
通讯作者：
Nayakshin, S.
中科院分区：
文献类型：
--
作者：
Humphries, J.;Vazan, A.;Nayakshin, S.
直接成像（DI）调查表明，超过20 Au的气体巨星是罕见的FGK恒星周围。然而，由于间隙开放和迁移效率的不确定性，尚不清楚这对引力不稳定性（GI）原行星的形成频率意味着什么。在这里，我们结合联合收割机国家的最先进的计算均匀的行星收缩与人口合成代码。我们发现DI约束是满足的，如果原行星形成GI发生在百分之几十的系统，如果原行星supermigrate的小分离。相比之下，如果原行星仍然滞留在宽轨道上，因为它们的迁移被有效的间隙打开所抑制，那么GI可能只发生在百分之几的系统中。然后，我们使用5 Au内径向速度测量中大质量巨星的频率来打破这种简并-最近的观测表明，这种人口与宿主星星金属丰度无关，因此怀疑是通过GI然后向内迁移形成的。我们发现，只有超迁移的情况下，可以充分解释这个人口，同时满足DI约束，并产生正确的质量谱内的行星5 Au。如果5 Au内的巨大气体巨星通过GI形成，那么我们的模型意味着迁移必须是有效的，并且GI原行星的形成至少发生在百分之几十的系统中。
Direct imaging (DI) surveys suggest that gas giants beyond 20 au are rare around FGK stars. However, it is not clear what this means for the formation frequency of gravitational instability (GI) protoplanets due to uncertainties in gap opening and migration efficiency. Here we combine state-of-the-art calculations of homogeneous planet contraction with a population synthesis code. We find DI constraints to be satisfied if protoplanet formation by GI occurs in tens ofpercent of systems if protoplanets supermigrate' to small separations. In contrast, GI may occur in only a fewpercent of systems if protoplanets remain stranded at wide orbits because their migration is quenched' by efficient gap opening. We then use the frequency of massive giants in radial velocity surveys inside 5 au to break this degeneracy - observations recently showed that this population does not correlate with the host star metallicity and is therefore suspected to have formed via GI followed by inward migration. We find that only the supermigration scenario can sufficiently explain this population while simultaneously satisfying the DI constraints and producing the right mass spectrum of planets inside 5 au. If massive gas giants inside 5 au formed via GI, then our models imply that migration must be efficient and that the formation of GI protoplanets occurs in at least tens ofpercent of systems.