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

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 ± 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.

Available online at: https://www.aanda.org/articles/aa/abs/2014/11/aa25099-14/aa25099-14.html

Bibliographic Code: 2014A&A...571L...5J