Based on data obtained with the European southern observatory Very Large Telescope, Paranal, Chile, programme 070A-9007(A) and on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.

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For simplicity, we use throughout the paper the same abbreviation, i.e. SFR, for different determinations of the parameter ``SFR'' (e.g. from photometry, spectroscopy, etc.). These determinations are not necessarily equivalent, as the different tracers probe the SFR over different timescales.

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... $\tau _V$

For a full explanation of our dust model, see Charlot & Fall (2000).

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... parameter

In the framework of the hierarchical model of galaxy formation it is actually also questionable, whether it has any physical meaning.

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... log (SFR) = -0.2

This is a crude estimate for the SFR equivalent to the detection limit for the [OII] emission line. Here we are only interested in a rough estimate of the size of the potential correction. A more detailed study, which is beyond the scope of the present paper, would have to take into account how this limit varies with redshift and would need to make a more complex model, in which bursts can have a range of durations.

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