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Can we really pick and choose? Benchmarking various selections of accreted halo stars in observations with simulations

Presentation #201.05 in the session Cosmological Footprints in Local Group dynamics.

Published onApr 25, 2022
Can we really pick and choose? Benchmarking various selections of accreted halo stars in observations with simulations

Through large spectroscopic surveys providing chemistry for >106 stars, and Gaia mapping >109 stars in the Galaxy, we have learned that the inner stellar halo is dominated by the accretion of Gaia Enceladus ~10 Gyr ago. With the richness of data at hand, there are a myriad of ways these accreted stars have been selected: from kinematics, to dynamics, to even chemistry. In this work, we explore these different selections and their effects on the inferred progenitor properties (i.e., stellar and total masses) using APOGEE DR17 and Gaia data. Specifically, we investigate the selections made in eccentricity, E-Lz, Vphi-Vr, Jr-Lz, and [Mg/Mn] vs [Al/Fe] and quantify the overlap between and contamination in each selection method. To ultimately understand their efficacy, we apply similar selections in a Milky Way like galaxy with a known Gaia Enceladus progenitor in the AURIGA hydrodynamical simulations and similarly infer progenitor properties. Through this, we aim to understand which selection is best to recover true Gaia Enceladus stars, and how much contamination from other accretion events and from in-situ population is present depending on the selection.


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