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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2018

Chemical characterization of the inner Galactic bulge:North–South symmetry

Résumé

While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly, the inner Galactic bulge (|b| < 2°) remains poorly studied, due to heavy interstellar absorption and photometric crowding. We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength range of 2.0818-2.1444 μ m with the resolution of R ˜ 50 000 and have signal-to-noise ratio of 50:100. Our stars are located along the bulge minor axis at l = 0°, b= ±0°, ±1°, ±2°, and +3°. Our sample was analysed in a homogeneous way using the most current K-band line list. We clearly detect a bimodal metallicity distribution function with a metal-rich peak at ˜ +0.3 dex and a metal-poor peak at ˜ -0.5 dex and no stars with [Fe/H] > +0.6 dex. The Galactic Centre field reveals in contrast a mainly metal-rich population with a mean metallicity of +0.3 dex. We derived [Mg/Fe] and [Si/Fe] abundances that are consistent with trends from the outer bulge. We confirm for the supersolar metallicity stars the decreasing trend in [Mg/Fe] and [Si/Fe] as expected from chemical evolution models. With the caveat of a relatively small sample, we do not find significant differences in the chemical abundances between the Northern and the Southern fields; hence, the evidence is consistent with symmetry in chemistry between North and South.
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Dates et versions

hal-02280918 , version 1 (04-05-2023)

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G. Nandakumar, N. Ryde, M. Schultheis, B. Thorsbro, H. Jonsson, et al.. Chemical characterization of the inner Galactic bulge:North–South symmetry. Monthly Notices of the Royal Astronomical Society, 2018, 478 (4), pp.4374-4389. ⟨10.1093/mnras/sty1255⟩. ⟨hal-02280918⟩
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