Can we really pick and choose? Benchmarking various selections of Gaia Enceladus/Sausage stars in observations with simulations
Can we really pick and choose? Benchmarking various selections of Gaia Enceladus/Sausage stars in observations with simulations
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我们真的可以挑选吗？
DOI：
10.1093/mnras/stad3274
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发表时间：
2024
影响因子：
4.8
通讯作者：
Carrillo A
中科院分区：
文献类型：
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作者：
Carrillo A
大型光谱测量和GAIA天体测量表明，银河系内部的恒星晕主要是GAIAEnceladus/香肠(GES)的碎片。随着手头数据的丰富，有无数种方法来选择这些吸积的恒星。我们使用远地点和Gaia构造的数据研究了这些GES选择及其对推断的祖先属性的影响。我们在观测中探索了偏心率、能量角动量(E-LZ)、径向作用角动量(JR-LZ)、作用钻石和[Mg/Mn]-[Al/Fe]的选择，选择了144到1279颗受到不同污染的GES恒星和其他吸积星。我们还利用Auriga宇宙流体动力学模拟对不同的GES动力学选择进行了基准测试。对九个具有GES的御夫座星系应用相同的观测GES切割，我们发现JR-LZ方法对于样品纯度是最好的，而偏心法对于完整性是最好的。给定GeS(−1.28<；[Fe/H]<；−1.18)的平均金属丰度，我们利用z=0质量-金属丰度关系求出∼4×108M⊙的平均值。我们采用了类似的方法，并对Auriga中的类GES系统进行了推导，发现偏心法高估了∼2.6X，而E-LZ低估了∼0.7X。最后，我们利用金属丰度梯度与GES与原位能比之间的关系估算了GES的总质量。归根结底，我们不能仅仅‘挑选’我们选择GES恒星的方式，而是应该受到科学问题的激励。
Large spectroscopic surveys plusGaiaastrometry have shown us that the inner stellar halo of the Galaxy is dominated by the debris ofGaiaEnceladus/Sausage (GES). With the richness of data at hand, there are a myriad of ways these accreted stars have been selected. We investigate these GES selections and their effects on the inferred progenitor properties using data constructed from APOGEE andGaia. We explore selections made in eccentricity, energy-angular momentum (E-Lz), radial action-angular momentum (Jr-Lz), action diamond, and [Mg/Mn]-[Al/Fe] in the observations, selecting between 144 and 1279 GES stars with varying contamination fromin-situand other accreted stars. We also use the Auriga cosmological hydrodynamic simulations to benchmark the different GES dynamical selections. Applying the same observational GES cuts to nine Auriga galaxies with a GES, we find that the Jr-Lz method is best for sample purity and the eccentricity method for completeness. Given the average metallicity of GES (−1.28 < [Fe/H] < −1.18), we use thez= 0 mass–metallicity relationship to find an averageof ∼4 × 108M⊙. We adopt a similar procedure and derivefor the GES-like systems in Auriga and find that the eccentricity method overestimates the trueby ∼2.6 × while E-Lz underestimates by ∼0.7 ×. Lastly, we estimate the total mass of GES to beusing the relationship between the metallicity gradient and the GES-to-in-situenergy ratio. In the end, we cannot just ‘pick and choose’ how we select GES stars, and instead should be motivated by the science question.