... abundances

Table 1 is only available in electronic form at http://www.edpsciences.org

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...R

R₂₃ = ([OII]$\lambda$3727 + [OIII]$\lambda$$\lambda$4959,5007)/H$\beta$.

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...S

S₂₃ = ([SII]$\lambda$$\lambda$6717,31 + [SIII]$\lambda$$\lambda$9069,9532)/H$\beta$.

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... SDSS-DR3

Data Release 3 of Sloan Digital Sky Survey.

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... telescope

Operated within the agreement between Brazil and ESO.

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... IRAF

IRAF is distributed by the National Optical Astronomy Observatories.

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... N2

N2 = log ([NII]$\lambda$6584/H$\alpha$).

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...S

The S₂₃ values were derived using the sulfur emission lines quoted in Table 1.

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...R

The R₂₃ values were calculated using the oxygen emission lines from our blue spectra (Kehrig et al. 2004).

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... [SIII]/[SII]

[SIII]/[SII] = [SIII]$\lambda$$\lambda$9069,9532/[SII]$\lambda$$\lambda$6717,6731.

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... solar

12+log (S/H)$_\odot$ = 7.19 $\pm$ 0.04 (Lodders 2003).

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... database

leda.univ-lyon1.fr (Paturel 2003).

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