Non-local thermodynamic equilibrium stellar spectroscopy with 1D and 3D models - II. Chemical properties of the Galactic metal-poor disk and the halo

Publication: Research - peer-reviewJournal article

  • Maria Bergemann
    Maria Bergemann
  • Remo Collet
  • Ralph Schönrich
    Ralph Schönrich
  • Rene Andrae
    Rene Andrae
  • Mikhail Kovalev
    Mikhail Kovalev
  • Gregory Ruchti
    Gregory Ruchti
  • Camilla J. Hansen
    Camilla J. Hansen
  • Zazralt Magic
    Zazralt Magic
We have analysed high-resolution spectra of 328 stars and derived Mg abundances using non-local thermodynamic equilibrium (NLTE) spectral line formation calculations and plane-parallel model stellar atmospheres derived from the mean stratification of 3D hydrodynamical surface convection simulations of late-type stars. The distribution of Mg abundances in the Galactic disk is analysed from the perspective of Galactic chemical evolution. We find that the trend of [Mg/Fe] shows a mild decline with decreasing metallicity below [Fe/H]~-1.2 and that a significant fraction of low-metallicity stars have [Mg/Fe] ratios close to solar even at [Fe/H] ~ -2. This is at variance with results of classical abundance analyses based on local thermodynamic equilibrium (LTE) and 1D model stellar atmospheres, which argue for a constant elevated [Mg/Fe] in metal-poor stars of the Galactic thick disk and halo.
Original languageEnglish
JournalarXiv
StatePublished - 1 Dec 2016

    Keywords

  • Astrophysics - Solar and Stellar Astrophysics

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