Toward a deterministic model of planetary formation. II. The formation and retention of gas giant planets around stars with a range of metallicities
Toward a deterministic model of planetary formation. II. The formation and retention of gas giant planets around stars with a range of metallicities
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DOI：
10.1086/424830
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发表时间：
2004-11-20
影响因子：
4.9
通讯作者：
Lin, DNC
中科院分区：
文献类型：
--
作者：
Ida, S;Lin, DNC
采用确定性的核-吸积行星形成模型，用蒙特卡罗模拟研究了太阳系外行星的探测频率与其主星的金属丰度的明显依赖关系。根据这个模型，气体巨星通过行星小凝聚形成并获得它们的质量M-p，随后出现了吸积气体的核心。这些原行星通过潮汐与其新生圆盘的相互作用，迁移并达到其渐近的半长轴a。根据观测到的原恒星盘的性质，我们得到了M-P-a分布。我们的结果重现了观测到的中等质量M-p=10-100M圆正数且小于或类似于3AU且大质量M-p大于或接近10(3)M圆正数且小于或类似于0.2AU的行星。基于模拟的M-p-a分布，我们还评估了目前的径向速度测量可以探测到的行星所在恒星的金属丰度相关性。如果原恒星盘含有与其宿主恒星相同的重元素，那么在富金属恒星周围的探测概率将大大提高，因为在这些恒星中形成的原行星核可以在耗尽之前增长到几个地球质量。这些巨大的质量是核心启动快速气体吸积并转变为巨型行星所必需的。理论外推的金属丰度依赖关系与观测结果一致。这种关联并不是在引力不稳定的情况下自然产生的。我们还提出了行星分布的其他金属丰度依赖关系，可以通过正在进行的观测进行测试。
The apparent dependence of detection frequency of extrasolar planets on the metallicity of their host stars is investigated with Monte Carlo simulations using a deterministic core-accretion planet formation model. According to this model, gas giants formed and acquired their mass M-p through planetesimal coagulation followed by the emergence of cores onto which gas is accreted. These protoplanets migrate and attain their asymptotic semimajor axis a through tidal interaction with their nascent disk. Based on the observed properties of protostellar disks, we generate an M-p-a distribution. Our results reproduce the observed lack of planets with intermediate mass M-p = 10-100 M-circle plus and a less than or similar to 3 AU and with large mass M-p greater than or similar to 10(3) M-circle plus and a less than or similar to 0.2 AU. Based on the simulated M-p-a distributions, we also evaluate the metallicity dependence of the fraction of stars harboring planets that are detectable with current radial velocity surveys. If protostellar disks attain the same fraction of heavy elements as contained in their host stars, the detection probability around metal-rich stars would be greatly enhanced because protoplanetary cores formed in them can grow to several Earth masses prior to their depletion. These large masses are required for the cores to initiate rapid gas accretion and to transform into giant planets. The theoretically extrapolated metallicity dependence is consistent with the observations. This correlation does not arise naturally in the gravitational-instability scenario. We also suggest other metallicity dependences of the planet distributions that can be tested by ongoing observations.