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Low-alpha stars in the Gaia-ESO survey: exotic travellers in our galaxy
Xiaoting FU (KAVLI - Peking University)
Tuesday 01/10/2019 @ 14:30, Sala IV piano Battiferro
We exploit the large high-resolution spectroscopic survey Gaia-ESO and the Gaia astrometry to study the properties of the population of low-alpha stars, which are thought to be formed in dwarf galaxies and later accreted into the Milky Way. In total, we select 43 low-alpha stars belonging both to the Galactic bulge, disc, and the halo. They show significantly lower [Mg/Fe] abundance compared to other Galactic field stars with similar [Fe/H] but are similar to stars belonging to dwarf galaxies. By considering their kinematic and dynamical parameters, we conclude that half of them are likely to be associated with Gaia-Enceladus, which has recently been proposed as a major accreted component of the local halo. Seven of the selected low-alpha stars belong to, at least are locate in, the Galactic bulge. The origin of the rest low-alpha stars are still unknown.