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Probing 3D and NLTE models using APOGEE observations of globular cluster stars
- Source :
- Astronomy & Astrophysics. 647:A24
- Publication Year :
- 2021
- Publisher :
- EDP Sciences, 2021.
-
Abstract
- Hydrodynamical (or 3D) and non-local thermodynamic equilibrium (NLTE) effects are known to affect abundance analyses. However, there are very few observational abundance testsof 3D and NLTE models. We developed a new way of testing the abundance predictions of 3D and NLTE models, taking advantage of large spectroscopic survey data. We use a line-by-line analysis of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra (H band) with the Brussels Automatic Code for Characterizing High accUracy Spectra (BACCHUS). We compute line-by-line abundances of Mg, Si, Ca, and Fe for a large number of globular cluster K giants in the APOGEE survey. We compare this line-by-line analysis against NLTE and 3D predictions. While the 1D-NLTE models provide corrections in the right direction, there are quantitative discrepancies between different models. We observe a better agreement with the data for the models including reliable collisional cross-sections. The agreement between data and models is not always satisfactory when the 3D spectra are computed in LTE. However, we note that for a fair comparison, 3D corrections should be computed with self-consistently derived stellar parameters, and not on 1D models with identical stellar parameters. Finally, we focus on 3D and NLTE effects on Fe lines in the H band, where we observe a systematic difference in abundance relative to the value from the optical. Our results suggest that the metallicities obtained from the H band are more accurate in metal-poor giants. More atomic data and extended self-consistent 3D-NLTE computations need to be made. The method we have developed for testing 3D and NLTE models could be extended to other lines and elements, and is particularly suited for large spectroscopic surveys.<br />Comment: 13 pages, 9 figures, accepted in A&A
- Subjects :
- Physics
010308 nuclear & particles physics
Thermodynamic equilibrium
FOS: Physical sciences
Astronomy and Astrophysics
Context (language use)
Astrophysics
Astrophysics - Astrophysics of Galaxies
01 natural sciences
Spectral line
Stars
Astrophysics - Solar and Stellar Astrophysics
Space and Planetary Science
Abundance (ecology)
Observatory
Astrophysics of Galaxies (astro-ph.GA)
Globular cluster
0103 physical sciences
Radiative transfer
Astrophysics::Solar and Stellar Astrophysics
010303 astronomy & astrophysics
Astrophysics::Galaxy Astrophysics
Solar and Stellar Astrophysics (astro-ph.SR)
Subjects
Details
- ISSN :
- 14320746 and 00046361
- Volume :
- 647
- Database :
- OpenAIRE
- Journal :
- Astronomy & Astrophysics
- Accession number :
- edsair.doi.dedup.....84d3f52a7469280eb8e9e1bbc5c5b895