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

Howes, L.; Asplund, Martin; Casey, A. R.; Keller, S. C.; Yong, D.; Gilmore, G.; Lind, K.; Worley, C.; Bessell, M. S.; Casagrande, Luca; Marino, A. F.; Nataf, D. M.; Owen, C. I.; Da Costa, Gary; Schmidt, Brian; Tisserand, Patrick; Randich, S.; Feltzing, S.; Vallenari, A.; Prieto, C. Allende; 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.

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

Date

2014-09-29

Authors

Howes, L.

Asplund, Martin

Casey, A. R.

Keller, S. C.

Yong, D.

Gilmore, G.

Lind, K.

Worley, C.

Bessell, M. S.

Casagrande, Luca

Publisher

Oxford University Press

Abstract

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.