Astronomy & Astrophysics

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{0101.f1.ps}\end{figure}$ Figure 1: Typical spectra of the a) low-excitation and b) high-excitation H II regions from the SDSS EDR. The spectra are transformed to a linear wavelength scale and zero redshift.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8.65cm,clip]{0101.f2.ps} % \end{figure}$ Figure 2: Diagnostic diagram [O III] $\lambda$ 5007/H $\beta$ vs. [N II] $\lambda$ 6583/H $\alpha$ for low-metallicity emission-line galaxies from the EDR of the SDSS. The dashed line separates the H II regions from galaxies ionized by a non-thermal radiation (labeled "AGN'') (Osterbrock 1989).
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8.6cm,clip]{0101.f3.ps}\end{figure}$ Figure 3: He I $\lambda$ 5015/H $\beta$ emission line flux ratio as a function of the oxygen abundance. The solid line is the mean ratio and the dashed lines are 1 $\sigma$ alternatives.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{0101.f4a.ps}\hspace*{1.1cm} \includegraphics[width=7.2cm,clip]{0101.f4b.ps}\end{figure}$ Figure 4: log N/O a), log Ar/O b), log Ne/O c), log S/O d) and log Fe/O e) vs. oxygen abundance 12 + log O/H for the HeBCD and SDSS galaxies. Filled circles are the HeBCD galaxies, open circles are the SDSS galaxies with [O III] $\lambda$ 4959/H $\beta$ $\geq$ 0.7 and asterisks are the SDSS galaxies with [O III] $\lambda$ 4959/H $\beta$ < 0.7. Solar abundance ratios from Lodders (2003) are shown by solid lines.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{0101.f5a.ps}\hspace*{1cm} \includegraphics[width=7.2cm,clip]{0101.f5b.ps}\end{figure}$ Figure 5: Same as in Fig. 4, but after correction of the electron temperature $T_{\rm e}$ (O III) in the SDSS galaxies with [O III] $\lambda$ 4959/H $\beta$ < 0.7 (asterisks).
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8cm,clip]{0101.f6a.ps}\hspace*{6mm} \includegraphics[angle=270,width=8.3cm,clip]{0101.f6b.ps}\end{figure}$ Figure 6: a) The Ne/O abundance ratios for our sample galaxies as a function of O⁺⁺/O⁺ ratio (same symbols as Fig. 4). The dashed line shows the trend of the data derived from the observations. The solid line shows the ionization correction factor ICF(Ne) as derived from photoionization models with metallicity $Z = Z_\odot$ /5 (see text). b) The observed values of O⁺⁺/O⁺ as a function of 12 + log O/H.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{0101.f7.ps}\end{figure}$ Figure 7: Nitrogen-to-oxygen abundance ratio, log N/O, vs. equivalent width of H $\beta$ emission line, EW(H $\beta$ ), for the galaxies in three metallicity bins defined as in Stasinska & Izotov (2003).
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{0101.f1.ps}\end{figure}$	Figure 1: Typical spectra of the a) low-excitation and b) high-excitation H II regions from the SDSS EDR. The spectra are transformed to a linear wavelength scale and zero redshift.
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$\begin{figure} \par\includegraphics[angle=270,width=8.65cm,clip]{0101.f2.ps} % \end{figure}$	Figure 2: Diagnostic diagram [O III] $\lambda$ 5007/H $\beta$ vs. [N II] $\lambda$ 6583/H $\alpha$ for low-metallicity emission-line galaxies from the EDR of the SDSS. The dashed line separates the H II regions from galaxies ionized by a non-thermal radiation (labeled "AGN'') (Osterbrock 1989).
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$\begin{figure} \par\includegraphics[angle=270,width=8.6cm,clip]{0101.f3.ps}\end{figure}$	Figure 3: He I $\lambda$ 5015/H $\beta$ emission line flux ratio as a function of the oxygen abundance. The solid line is the mean ratio and the dashed lines are 1 $\sigma$ alternatives.
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$\begin{figure} \par\includegraphics[width=8.7cm,clip]{0101.f5a.ps}\hspace*{1cm} \includegraphics[width=7.2cm,clip]{0101.f5b.ps}\end{figure}$	Figure 5: Same as in Fig. 4, but after correction of the electron temperature $T_{\rm e}$ (O III) in the SDSS galaxies with [O III] $\lambda$ 4959/H $\beta$ < 0.7 (asterisks).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{0101.f7.ps}\end{figure}$	Figure 7: Nitrogen-to-oxygen abundance ratio, log N/O, vs. equivalent width of H $\beta$ emission line, EW(H $\beta$ ), for the galaxies in three metallicity bins defined as in Stasinska & Izotov (2003).
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