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arXiv · 1410.6415

The Gaia-ESO Survey: α-abundances of metal-poor stars

R. Jackson-Jones·P. Jofré·K. Hawkins·A. Hourihane·G. Gilmore·G. Kordopatis·C. Worley·S. Randich·A. Vallenari·T. Bensby·A. Bragaglia·E. Flaccomio·A. J. Korn·A. Recio-Blanco·R. Smiljanic·M. T. Costado·U. Heiter·V. Hill·C. Lardo·P. de Laverny·G. Guiglion·S. Mikolaitis·S. Zaggia·G. Tautvaišiene
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Abstract

We performed a detailed study of the ratio of low-α to high-α stars in the Galactic halo as observed by the Gaia-ESO Survey. Using a sample of 381 metal-poor stars from the second internal data release, we found that the value of this ratio did not show evidence of systematic trends as a function of metallicity, surface gravity, Galactic latitude, Galactic longitude, height above the Galactic plane, and Galactocentric radius. We conclude that the α-poor/α-rich value of 0.28 $\pm$ 0.08 suggests that in the inner halo, the larger portion of stars were formed in a high star formation rate environment, and about 15% of the metal-poor stars originated from much lower star formation rate environments.

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R. Jackson-Jones, P. Jofré, K. Hawkins, A. Hourihane, G. Gilmore, G. Kordopatis, C. Worley, S. Randich, A. Vallenari, T. Bensby, A. Bragaglia, E. Flaccomio, A. J. Korn, A. Recio-Blanco, R. Smiljanic, M. T. Costado, U. Heiter, V. Hill, C. Lardo, P. de Laverny, G. Guiglion, S. Mikolaitis, S. Zaggia, G. Tautvaišiene. 2014-10-23. The Gaia-ESO Survey: α-abundances of metal-poor stars. https://doi.org/10.1051/0004-6361%2F201425099

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