All Figures

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg01.ps}\end{figure}$ Figure 1: Temperature-magnitude diagram of unevolved near-turnoff stars, based on HIPPARCOS parallaxes. Filled circles refer to stars observed, open circles to the rest of the sample with temperatures approximated from a simple B-V vs. $T_{\rm eff}$ correlation. Symbol sizes increase with the $\delta$ (U-B) excesses in the three intervals [0.10-0.14], [0.14-0.20] and >0.20. Star symbols denote peculiar stars (binaries etc.). The zero age main sequence for [Fe/H] = -1.5 is plotted for comparison. The two stars at the extreme left are G9-16 and HD 128167, that on the lower right is HD 103095.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{4434fg02.eps} \end{figure}$ Figure 2: Double-lined spectra detected in the sample. The components have been marked for the Cr I 201 line at 5254.98 Å. The flux axis is compressed to show approximately the same dynamic range for each star. See text for details.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{4434fg03.ps} \end{figure}$ Figure 3: Comparison of effective temperatures derived from the infrared flux method (Alonso et al. 1996; Blackwell & Lynas-Gray 1997) and from Balmer lines (this paper). Open circles refer to the metal-poor reference stars, filled circles represent the standard sample.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg04.ps} \end{figure}$ Figure 4: $\alpha$ -element ratio [Mg/Fe] as a function of metal abundance. Filled circles represent our sample, open circles are the metal-poor reference stars. Symbol size refers to $\delta$ (U-B) excesses as in Fig. 1.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg5a.ps}\par\vspace{2mm} \includegraphics[width=9cm,clip]{4434fg5b.ps} \end{figure}$ Figure 5: Element ratios [Na/Mg] ( top) and [Al/Mg] ( bottom) as a function of the metal abundance [Fe/H]. Symbols have the same meaning as in Fig. 4.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg06.ps} \end{figure}$ Figure 6: Element ratio [Al/Mg] as a function of the ratio [Mg/Fe]. Note the separation between the Al-rich and the Al-poor stars at [Al/Mg] = -0.1.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg07.ps} \end{figure}$ Figure 7: Difference of element abundance ratios calculated under NLTE and LTE assumptions, respectively.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg08.ps}\end{figure}$ Figure 8: Galactic space velocities of the stellar sample. Open symbols refer to the extremely metal-poor reference sample, filled symbols to the metal-poor standard sample. Circles follow the requirement [Al/Mg] < -0.10, triangles require [Al/Mg] > -0.10, but [Mg/Fe] > 0.25, and squares represent stars with [Mg/Fe] < 0.25. Star symbols denote peculiar objects as defined in Table 1.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg09.ps} \end{figure}$ Figure 9: Correlation of asymmetric drift velocities and [Al/Mg] abundance ratios. Symbols are the same as in Fig. 8.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg10.ps} \end{figure}$ Figure 10: Correlation of stellar ages and [Al/Mg] abundance ratios. Symbols are the same as in Fig. 8.
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{4434f11a.ps}\par\vspace*{2mm} \includegraphics[width=9cm,clip]{4434f11b.ps} \end{figure}$ Figure 11: Galactic evolution of [Na/Mg] and [Al/Mg] abundance ratios. Abundances are the same as in Fig. 5. The theoretical curves are from Timmes et al. (1995).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{4434fg02.eps} \end{figure}$	Figure 2: Double-lined spectra detected in the sample. The components have been marked for the Cr I 201 line at 5254.98 Å. The flux axis is compressed to show approximately the same dynamic range for each star. See text for details.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{4434fg03.ps} \end{figure}$	Figure 3: Comparison of effective temperatures derived from the infrared flux method (Alonso et al. 1996; Blackwell & Lynas-Gray 1997) and from Balmer lines (this paper). Open circles refer to the metal-poor reference stars, filled circles represent the standard sample.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg04.ps} \end{figure}$	Figure 4: $\alpha$ -element ratio [Mg/Fe] as a function of metal abundance. Filled circles represent our sample, open circles are the metal-poor reference stars. Symbol size refers to $\delta$ (U-B) excesses as in Fig. 1.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg5a.ps}\par\vspace{2mm} \includegraphics[width=9cm,clip]{4434fg5b.ps} \end{figure}$	Figure 5: Element ratios [Na/Mg] ( top) and [Al/Mg] ( bottom) as a function of the metal abundance [Fe/H]. Symbols have the same meaning as in Fig. 4.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg06.ps} \end{figure}$	Figure 6: Element ratio [Al/Mg] as a function of the ratio [Mg/Fe]. Note the separation between the Al-rich and the Al-poor stars at [Al/Mg] = -0.1.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg07.ps} \end{figure}$	Figure 7: Difference of element abundance ratios calculated under NLTE and LTE assumptions, respectively.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg08.ps}\end{figure}$	Figure 8: Galactic space velocities of the stellar sample. Open symbols refer to the extremely metal-poor reference sample, filled symbols to the metal-poor standard sample. Circles follow the requirement [Al/Mg] < -0.10, triangles require [Al/Mg] > -0.10, but [Mg/Fe] > 0.25, and squares represent stars with [Mg/Fe] < 0.25. Star symbols denote peculiar objects as defined in Table 1.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg09.ps} \end{figure}$	Figure 9: Correlation of asymmetric drift velocities and [Al/Mg] abundance ratios. Symbols are the same as in Fig. 8.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434fg10.ps} \end{figure}$	Figure 10: Correlation of stellar ages and [Al/Mg] abundance ratios. Symbols are the same as in Fig. 8.
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$\begin{figure} \par\includegraphics[width=9cm,clip]{4434f11a.ps}\par\vspace*{2mm} \includegraphics[width=9cm,clip]{4434f11b.ps} \end{figure}$	Figure 11: Galactic evolution of [Na/Mg] and [Al/Mg] abundance ratios. Abundances are the same as in Fig. 5. The theoretical curves are from Timmes et al. (1995).
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