轨道偏心率作为厚盘形成情景的探测
Orbital Eccentricity as a probe of Thick Disk Formation Scenarios
摘要：
我们研究了四个（已发表）模拟厚盘形成的恒星的轨道特性：i）吸积从破坏的卫星，ii）加热预先存在的薄盘由一个小合并，iii）径向迁移和iv）气体丰富的合并。我们发现，轨道偏心率的分布预测是不同的每个模型：在低偏心率的一个突出的峰值预计加热，迁移和富含气体的合并方案，而偏心率分布更广泛，并向更高的值转移的吸积模型。这些差异可以追溯到在每种情况下，大部分恒星是“原位”形成的还是“吸积”的，并且对每个模型的特殊性都是鲁棒的。基于附近厚盘星偏心率分布的一个简单的测试可能有助于阐明银河系厚盘的主要形成机制。
英文摘要：
We study the orbital properties of stars in four (published) simulations of thick disks formed by: i) accretion from disrupted satellites, ii) heating of a pre-existing thin disk by a minor merger, iii) radial migration and iv) gas rich mergers. We find that the distribution of orbital eccentricities are predicted to be different for each model: a prominent peak at low eccentricity is expected for the heating, migration and gas-rich merging scenarios, while the eccentricity distribution is broader and shifted towards higher values for the accretion model. These differences can be traced back to whether the bulk of the stars in each case is formed 'in-situ' or is 'accreted', and are robust to the peculiarities of each model. A simple test based on the eccentricity distribution of nearby thick disk stars may thus help elucidate the dominant formation mechanism of the Galactic thick disk.
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