Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[height=5.66cm,width=8.7cm,clip]{Gd291_f1.eps} \end{figure}$ Figure 1: The iron index $\langle$ Fe $\rangle$ is plotted vs. the Balmer index $\langle$ H $\rangle$ for 430 MSTO/SGB stars (grey dots). A typical error is indicated on the left. Also shown are 11 standard stars (bold dots) with $-2.7<\rm [Fe/H]<-0.7$ dex. The bold curve marks a fit to the position of 32 MSTO/SGB stars of M 55. The other curves are iso-metallicity lines as measured from synthetic spectra. Their slope describes the temperature effect on $\langle$ Fe $\rangle$ (about 5000 to 7000 K from left to right).
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In the text

$\begin{figure} \par\includegraphics[height=6.95cm,width=18cm,clip]{Gd291_f2.eps} \end{figure}$ Figure 2: Comparison of the position of stars of different abundances with Yonsei-Yale isochrones of different ages and metallicities (as indicated in the upper left corners). The abundance ranges for the highlighted stars are: left: $-2.0<\rm [Fe/H]<-1.4$ , middle: $-1.4<\rm [Fe/H]<-1.0$ , right: $\rm [Fe/H]>-1.0$ dex. The diagonal line indicates the selection criterium for age estimates (Fig. 3).
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In the text

$\begin{figure} \par\includegraphics[height=8.6cm,width=8.6cm,clip]{Gd291_f3.eps} \end{figure}$ Figure 3: The age-metallicity relation for $\sim$ 250 SGB stars (redwards the diagonal line in Fig. 2) with [Fe/H] errors less than 0.2 dex and age errors less than 2 Gyr is shown. The metallicity and age distributions are also plotted (as histograms and binning independent density distributions). The hashed histograms represent M 55 stars (up-scaled by a factor of 3) which are supposed to have a single age and metallicity (-1.8 dex).
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In the text