Fernandez-Alvar, EmmaTissera, Patricia B.Carigi, LeticiaSchuster, William J.Beers, Timothy C.Belokurov, Vasily A.2023-06-192023-06-192019-02-15Monthly Notices of the Royal Astronomical Society Volume 485, Issue 2, Pages 1745 - 1756 15 February 20190035-8711https://repositorio.unab.cl/xmlui/handle/ria/50804Indexación ScopusWe explore the origin of the observed decline in [O/Fe] (and [Mg/Fe]) with Galactocentric distance for high-metallicity stars ([Fe/H] > −1.1), based on a sample of halo stars selected within the Apache Point Observatory Galactic Evolution Experiment (APOGEE) fourteenth data release (DR14). We also analyse the characteristics of the [α/Fe] distributions in the inner-halo regions inferred from two zoom-in Milky Way mass-sized galaxies that are taken as case studies. One of them qualitatively reproduces the observed trend to have higher fraction of α-rich star for decreasing galactocentric distance; the other exhibits the opposite trend. We find that stars with [Fe/H] > −1.1 located in the range [15–30] kpc are consistent with formation in two starbursts, with maxima separated by about ∼1 Gyr. We explore the contributions of stellar populations with different origin to the [α/Fe] gradients detected in stars with [Fe/H] > −1.1. Our analysis reveals that the simulated halo that best matches the observed chemical trends is characterized by an accretion history involving low-to intermediate-mass satellite galaxies with a short and intense burst of star formation, and contributions from a more massive satellite with dynamical masses about ∼1010 M, distributing low [α/Fe] stars at intermediate radius.enGalaxy: abundancesGalaxy: formationGalaxy: haloMethods: numericalTechniques: spectroscopicArtículoAttribution 4.0 International (CC BY 4.0)10.1093/mnras/stz443