Oxygen in the Early Galaxy: OH Lines as Tracers of Oxygen Abundance in Extremely Metal-Poor Giant Stars
Abstract
Oxygen is a powerful tracer element of Galactic chemical evolution. Unfortunately, only a few oxygen lines are available in the ultraviolet-infrared stellar spectra for the reliable determination of its abundance. Moreover, oxygen abundances obtained using different spectral lines often disagree significantly. In this contribution we therefore investigate whether the inadequate treatment of convection in 1D hydrostatic model atmospheres used in the abundance determinations may be responsible for this disagreement. For this purpose, we used VLT CRIRES spectra of three EMP giants, as well as 3D hydrodynamical COBOLD and 1D hydrostatic LHD model atmospheres, to investigate the role of convection in the formation of infrared (IR) OH lines. Our results show that the presence of convection leads to significantly stronger IR OH lines. As a result, the difference in the oxygen abundance determined from IR OH lines with 3D hydrodynamical and classical 1D hydrostatic model atmospheres may reach -0.2 dots -0.3 dex. In case of the three EMP giants studied here, we obtain a good agrement between the 3D LTE oxygen abundances determined by us using vibrational-rotational IR OH lines in the spectral range of 1514-1626 nm, and oxygen abundances determined from forbidden [O I] 630 nm line in previous studies.
- Publication:
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18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun
- Pub Date:
- January 2015
- DOI:
- 10.48550/arXiv.1409.3153
- arXiv:
- arXiv:1409.3153
- Bibcode:
- 2015csss...18..327K
- Keywords:
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- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 7 pages, 2 figures, Proceedings of Cool Stars, Stellar Systems and the Sun 18