Astronomy & Astrophysics manuscript no. dias˙et˙al˙2014b c ESO 2018 October 8, 2018 FORS2/VLT survey of Milky Way globular clusters I. Description of the method for derivation of metal abundances in the optical and application to NGC 6528, NGC 6553, M 71, NGC 6558, NGC 6426 and Terzan 8 ⋆ B. Dias1,2, B. Barbuy1, I. Saviane2, E. V. Held3, G. S. Da Costa4, S. Ortolani3,5, S. Vasquez2,6, M. Gullieuszik3, and D. Katz7 1 Universidade de S˜ao Paulo, Dept. de Astronomia, Rua do Mat˜ao 1226, S˜ao Paulo 05508-090, Brazil e-mail:
[email protected] 2 European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile 3 INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy 4 Research School of Astronomy & Astrophysics, Australian National University, Mount Stromlo Observatory, via Cotter Road, Weston Creek, ACT 2611, Australia 5 Universit`adi Padova, Dipartimento di Astronomia, Vicolo dell’Osservatorio 2, 35122 Padova, Italy 6 Instituto de Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22, Chile 7 GEPI, Observatoire de Paris, CNRS, Universit´eParis Diderot, 5 Place Jules Janssen 92190 Meudon, France Received: ; accepted: ABSTRACT Context. We have observed almost 1/3 of the globular clusters in the Milky Way, targeting distant and/or highly reddened objects, besides a few reference clusters. A large sample of red giant stars was observed with FORS2@VLT/ESOat R∼2,000. The method for derivation of stellar parameters is presented with application to six reference clusters. Aims. We aim at deriving the stellar parameters effective temperature, gravity, metallicity and alpha-element enhancement, as well as radial velocity, for membership confirmation of individual stars in each cluster.