All Figures

$\begin{figure} \par\includegraphics[angle=-90,width=5.5cm,clip]{4845fig1a.ps}\hs... ...*{3mm} \includegraphics[angle=-90,width=5.5cm,clip]{4845fig1i.ps} \end{figure}$ Figure 1: Line strengths of LDEGs (open symbols) and HDEGs (filled symbols) through the central aperture. The distinct symbols indicate different kind of galaxies: triangles correspond to dwarf ellipticals, squares to lenticulars, and circles to normal ellipticals. Model grids from V06 have been superposed: solid lines are contours of constant age (1.0, 1.41, 2.00, 2.82, 3.98, 5.62, 7.98, 11.22, and 15.85 Gyr), and dashed lines are contours of constant [M/H] ([M/H] = -0.68, -0.38, 0.0, and +0.2 dex). The arrows indicate the direction of increasing age and metallicity. Three different metal indicators (CN₂, Fe4383, and Mgb) are combined with three different age-sensitive indexes (H $\beta$ , D4000, and H $\gamma _{\rm F}$ ).
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In the text

$\begin{figure} \par\includegraphics[width=10.2cm,clip]{4845fig2.ps} \end{figure}$ Figure 2: Relations between metallicities, obtained with different indicators, and age against velocity dispersion for the sample of galaxies. Open symbols represent galaxies in low-density environments (LDEGs), while filled symbols indicate galaxies in high density environments (HDEGs). Squares correspond to S0 galaxies, while elliptical galaxies are represented with circles. Grey and black lines show the linear fit, weighting with the errors in both axes, to the LDEGs and HDEGs respectively.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig3a.ps}\pa... ...b.ps}\par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig3c.ps} \end{figure}$ Figure 3: Relation of the age with the velocity dispersion for galaxies in the Coma cluster, Virgo cluster, and galaxies in the field and poor groups.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig4a.ps}\pa... ...mm} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig4b.ps} \end{figure}$ Figure 4: Comparison of the observed spectra of the galaxies NGC 4467 and NGC 3605 (black line) and the synthetic spectra from V06 (grey line). The lower panels show the difference between both spectra. The parameters of the synthetic spectra are shown in the panel.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig5.ps} \end{figure}$ Figure 5: Grey-scale diagram of the standard deviation in the residuals of the comparison of different synthetic spectra with the spectrum of NGC 4467. Darker squares represent lower residuals. The numbers indicate the combination of age and metallicity of the 9 best solutions, ordered from the lowest standard deviation (1) to the highest (9).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig6.ps} \end{figure}$ Figure 6: Distribution of ages obtained comparing the synthetic spectra from V06 with the spectral energy distribution of LDEGs. The empty histogram shows the ages obtained with the comparison in the spectral range 4750-5150 Å, while the shaded histogram the ages obtained comparing the region from 3650-4050 Å.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig7.ps} \end{figure}$ Figure 7: Distribution of ages obtained by comparing the synthetic spectra from the models of V06 with the observed spectra for the sample of HDEGs. The empty histogram represents the ages obtained in the spectral range 4750-5150 Å while the shaded histogram shows the calculated ages in the spectral range 3650-4050 Å.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{4845fig8.ps}\end{figure}$ Figure 8: Comparison of the ages derived in two different spectral ranges using the models of V06. The asterisks are the values calculated for the LDEG spectra, while the filled circles are the ages derived from the composite models in which two populations of different ages and metallicities are added (see text for details). The solid, dashed, and dotted lines connect the various two-component model combinations for the 30:70, 20:80, and 10:90 young:old population mass ratios, respectively. The age of the younger component increases from lower left to upper right of the diagram.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{4845fig9.ps} \end{figure}$ Figure 9: Differences between the fraction of light contributed by a burst of star formation with metallicity Z=+0.2 in two different spectral ranges (4750-51500 Å) and (3650-4050 Å) when added to a population of age = 15.85 Gyr and metallicity Z=-0.38for different ages of the burst.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig10.ps} \end{figure}$ Figure 10: Age-metallicity relation for LDEGs when the age and metallicity are derived from a Fe4383-H $\beta$ diagram.
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In the text

$\begin{figure} \par\mbox{\includegraphics[angle=-90,width=5cm,clip]{4845fig11a.p... ...mm} \includegraphics[angle=-90,width=5cm,clip]{4845fig11f.ps} } \end{figure}$ Figure 11: Top panels: index-index diagrams for 3 different fake populations with the following characteristics: from left to right, (1) age 8 Gyr and solar metallicity [M/H] = 0; (2) age 8 Gyr and metallicity between 0.0<[M/H]<0.06; (3) age between 5.6 and 10 Gyr and solar metallicity [M/H]=0. Small dots represent the results of the Monte Carlo simulations in which each point was perturbed following a Gaussian distribution with a standard deviation given by the typical error in Fe4383 and the H $\beta$ indices in the sample of LDEGs. Bottom panels: age-metallicity relation for each of the 3 fake distributions plotted on the upper panels. Dashed lines show the linear fit to these distributions. Grey circles show the age and metallicity for LDEGs and the solid lines represent the linear fit to these data.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig11g.ps} \end{figure}$ Figure 12: Comparison of the ages and metallicities obtained from completely independent diagrams for the LDEGs. The line represents a least-square fit, minimizing the residuals in both directions, x and y.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig12.ps} \end{figure}$ Figure 13: Age-metallicity relation for HDEGs, where the age and the metallicity have been measured in a Fe4383-H $\beta$ diagram. The solid line represents a least-square fit to the data minimising the residuals in both directions. The dashed line represents the best fit obtained for LDEGs.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig13a.ps}\p... ...m} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig13b.ps} \end{figure}$ Figure 14: Relation between the age and metallicity obtained for a mock distribution of points following the index- $\sigma$ relations (filled circles) and for this sample, perturbed with the observational errors (small dots). See the text for details.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig14.ps} \end{figure}$ Figure 15: Age metallicity relation for HDEGs where the age and the metallicity have been obtained from two independent diagrams. The line represent a least-square fit minimising the residuals in both directions, x and y.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig15.ps} \end{figure}$ Figure 16: Age-metallicity relation for the sample of low-density environment galaxies when these parameters are measured in a Mgb-H $\beta$ diagram. The line indicate a least-square fit to the data, minimizing the residuals in both directions x and y.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig3a.ps}\pa... ...b.ps}\par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig3c.ps} \end{figure}$	Figure 3: Relation of the age with the velocity dispersion for galaxies in the Coma cluster, Virgo cluster, and galaxies in the field and poor groups.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig4a.ps}\pa... ...mm} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig4b.ps} \end{figure}$	Figure 4: Comparison of the observed spectra of the galaxies NGC 4467 and NGC 3605 (black line) and the synthetic spectra from V06 (grey line). The lower panels show the difference between both spectra. The parameters of the synthetic spectra are shown in the panel.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig5.ps} \end{figure}$	Figure 5: Grey-scale diagram of the standard deviation in the residuals of the comparison of different synthetic spectra with the spectrum of NGC 4467. Darker squares represent lower residuals. The numbers indicate the combination of age and metallicity of the 9 best solutions, ordered from the lowest standard deviation (1) to the highest (9).
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$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig6.ps} \end{figure}$	Figure 6: Distribution of ages obtained comparing the synthetic spectra from V06 with the spectral energy distribution of LDEGs. The empty histogram shows the ages obtained with the comparison in the spectral range 4750-5150 Å, while the shaded histogram the ages obtained comparing the region from 3650-4050 Å.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{4845fig7.ps} \end{figure}$	Figure 7: Distribution of ages obtained by comparing the synthetic spectra from the models of V06 with the observed spectra for the sample of HDEGs. The empty histogram represents the ages obtained in the spectral range 4750-5150 Å while the shaded histogram shows the calculated ages in the spectral range 3650-4050 Å.
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$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{4845fig9.ps} \end{figure}$	Figure 9: Differences between the fraction of light contributed by a burst of star formation with metallicity Z=+0.2 in two different spectral ranges (4750-51500 Å) and (3650-4050 Å) when added to a population of age = 15.85 Gyr and metallicity Z=-0.38for different ages of the burst.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig10.ps} \end{figure}$	Figure 10: Age-metallicity relation for LDEGs when the age and metallicity are derived from a Fe4383-H $\beta$ diagram.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig11g.ps} \end{figure}$	Figure 12: Comparison of the ages and metallicities obtained from completely independent diagrams for the LDEGs. The line represents a least-square fit, minimizing the residuals in both directions, x and y.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig12.ps} \end{figure}$	Figure 13: Age-metallicity relation for HDEGs, where the age and the metallicity have been measured in a Fe4383-H $\beta$ diagram. The solid line represents a least-square fit to the data minimising the residuals in both directions. The dashed line represents the best fit obtained for LDEGs.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig13a.ps}\p... ...m} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig13b.ps} \end{figure}$	Figure 14: Relation between the age and metallicity obtained for a mock distribution of points following the index- $\sigma$ relations (filled circles) and for this sample, perturbed with the observational errors (small dots). See the text for details.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig14.ps} \end{figure}$	Figure 15: Age metallicity relation for HDEGs where the age and the metallicity have been obtained from two independent diagrams. The line represent a least-square fit minimising the residuals in both directions, x and y.
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$\begin{figure} \par\includegraphics[angle=-90,width=7.6cm,clip]{4845fig15.ps} \end{figure}$	Figure 16: Age-metallicity relation for the sample of low-density environment galaxies when these parameters are measured in a Mgb-H $\beta$ diagram. The line indicate a least-square fit to the data, minimizing the residuals in both directions x and y.
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