Based on observations collected at the European Southern Observatory, Chile (ESO Programme 70.A-0548), and on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

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Figures 2 and 3 are only available in electronic form at http://www.edpsciences.org

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...1,

Present address: ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany.

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... survey

See http://www.arcetri.astro.it/~k20/spe_release_dec04/index.html

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