We use the second Gaia data release (Gaia DR2), combined with RAVE spectroscopic surveys, to identify the substructures in the nearby stellar halo. We select 3,845 halo stars kinematically and chemically, and determine their density distribution in energy and angular momentum space. To select the substructures from overdensities, we reshuffle the velocities and estimate their significance. Two statistically significant substructures, GR-1 and GR-2, are identified. GR-1 has a high binding energy and small $z$-angular momentum. GR-2 is metal-rich but retrograde. They are both new substructure, and may be accretion debris of dwarf galaxies.

中文翻译：

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在 Gaia 和 RAVE 中发现的附近恒星光环中的两个子结构

我们使用第二个盖亚数据发布（盖亚 DR2），结合 RAVE 光谱调查，来识别附近恒星晕中的子结构。我们从运动学和化学上选择了 3,845 颗晕星，并确定了它们在能量和角动量空间中的密度分布。为了从超密度中选择子结构，我们重新调整速度并估计它们的重要性。确定了两个统计显着的子结构，GR-1 和 GR-2。GR-1 具有较高的结合能和较小的 $z$-角动量。GR-2 富含金属但会逆行。它们都是新的亚结构，可能是矮星系的吸积碎片。