Letter to the Editor

Oxygen abundances in the Galactic bulge: evidence for fast chemical enrichment

¹ P. Universidad Católica de Chile, Departamento de Astronomía y Astrofísica, Casilla 306, Santiago 22, Chile e-mail: [mzoccali;dante]@astro.puc.cl
² Observatoire de Paris-Meudon, 92195 Meudon Cedex, France e-mail: [Vanessa.Hill;Aurelie.Lecureur;Ana.Gomez]@obspm.fr
³ Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil e-mail: barbuy@astro.iag.usp.br
⁴ INAF - Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: renzini@pd.astro.it
⁵ Università di Padova, Dipartimento di Astronomia, Vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: [momany;ortolani]@pd.astro.it

Received: 22 May 2006
Accepted: 16 July 2006

Abstract

Aims.We spectroscopically characterize the Galactic Bulge to infer its star formation timescale, compared to the other Galactic components, through the chemical signature on its individual stars.

Methods.We derived iron and oxygen abundances for 50 K giants in four fields towards the Galactic bulge. High resolution () spectra for the target stars were collected with FLAMES-UVES at the VLT.

Results.Oxygen, as measured from the forbidden line at 6300 Å, shows a well-defined trend with [Fe/H], with [O/Fe] higher in bulge stars than in thick disk ones, which were known to be more oxygen enhanced than thin disk stars.

Conclusions.These results support a scenario in which the bulge formed before and more rapidly than the disk, and therefore the MW bulge can be regarded as a prototypical old spheroid, with a formation history similar to that of early-type (elliptical) galaxies.