The Gaia-ESO Survey: {\alpha}-abundances of metal-poor stars
  We performed a detailed study of the ratio of low-{\alpha} to high-{\alpha} 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 {\alpha}-poor/{\alpha}-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. 
R. Jackson-Jones, P. Jofr\'e, K. Hawkins, A. Hourihane, G. Gilmore, G.   Kordopatis, C. Worley, S. Randich, A. Vallenari, T....
astro-ph.GA