[1] Univ Florence, Dipartimento Astron & Sci Spazio, I-50125 Florence, Italy
[2] Isaac Newton Grp Telescopes, Santa Cruz De La Palma 38700, Canarias, Spain
[3] Inst Astrofis Canarias, San Cristobal la Laguna 38200, Tenerife, Spain
[4] ST, ECF, ESO, D-85748 Garching, Germany
[5] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[6] Univ Manchester, Dept Phys, Manchester M60 1QD, Lancs, England
[7] Pontificia Univ Catolica Chile, Dept Astron, Santiago 22, Chile