Program: GS-2006A-C-9

The Galactic bulge is the least studied stellar population in our Galaxy. Very little data is available in terms of its detailed abundance pattern which could give important information on the formation and chemical enrichment of the bulge. It is predicted that, if dissipational collapse occurred in the early Galaxy, the metal-poor bulge stars and globular clusters were among the very first objects which formed. We intend to observe 20 red giants in the metal-poor bulge globular clusters HP-1 and NGC 6558 using the Phoenix IR spectrograph. We have V and I colours obtained for these clusters with the ESO NTT and WFI@2.2m telescopes. The present proposal is a resubmission of previously granted time, but only 2 hours of the approved 2 nights in classical time, were useful. In these 2 hours in June 2005 we were able to observe 2 HP-1 stars using Phoenix at Gemini, and the spectra are excellent. The IR is ideal for the purpose given the low impact of reddening and the small amount of line-crowding in the stellar spectra, which allow the measurement of very accurate element abundances. The very scarce abundance information available for metal-poor bulge stars to date suggest significant differences with the halo population of similar metallicity for unknown reasons, which we intend to investigate. The proposed observations will enable the determination of the abundances of oxygen using the OH lines, that is the main purpose of this proposal, besides C, N, Fe and the alpha-element Ti, which will provide important insight to the nucleosynthetic enrichment during the earliest phases of our Galaxy.