The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge

Howes, L. M.; Asplund, M.; Casey, A. R.; Keller, S. C.; Yong, D.; Gilmore, G.; Lind, K.; Worley, C.; Bessell, M. S.; Casagrande, L.; Marino, A. F.; Nataf, D. M.; Owen, C. I.; Da Costa, G. S.; Schmidt, B. P.; Tisserand, P.; Randich, S.; Feltzing, S.; Vallenari, A.; Allende Prieto, C.; Bensby, T.; Flaccomio, E.; Korn, A. J.; Pancino, E.; Recio-Blanco, A.; Smiljanic, R.; Bergemann, M.; Costado, M. T.; Damiani, F.; Heiter, U.; Hill, V.; Hourihane, A.; Jofré, P.; Lardo, C.; de Laverny, P.; Magrini, L.; Maiorca, E.; Masseron, T.; Morbidelli, L.; Sacco, G. G.; Minniti, D.; Zoccali, M.
Monthly Notices of the Royal Astronomical Society, Volume 445, Issue 4, p.4241-4246 (2014).


We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilizes SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with -2.72 ≤ [Fe/H] ≤ -2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [α/Fe] ratios.