... Institute

Operated by AURA for NASA under contract NAS 5-26555.

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...$Z_\odot$

For 9 objects the electron temperature was too low for temperature sensitive ratios to be measured, and the metallicity was estimated with the strong line method (Pagel et al. 1979).

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... procedure

Plotting [O  III]/H$\beta$ vs. [O  II]/H$\beta$ from the Terlevich sample using line ratios not corrected for reddening results in a smaller scatter.

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... distributions

The predictions from these synthesis models are available on the Web at
http://webast.ast.obs-mip.fr/people/schaerer/

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... samples

Tables giving infrared, optical and ultraviolet line intensities for all the models discussed in this paper are available on the Web at
http://webast.ast.obs-mip.fr/people/schaerer/

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...$M_\odot$

A lower IMF mass cut-off of $M_{\rm low}$ = 0.8 $M_\odot$ was adopted.

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... HREF="/articles/aa/full/2001/16/aa10400/node2.html#fig3">3

Except He  I $\lambda$5876/H$\beta$ which is not available.

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...1999)

Although in general the hardness decreases with age, the temporary increase in the high metallicity models at 4 Myr is due to the appearance of WR stars at 3 Myr (cf. Fig. 5). The reality of this feature is, however, questionable (cf. Sect. 3.1).

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