All Figures

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{2434fg01.ps} \end{figure}$ Figure 1: The K20 (rectangle, centered at $03^{\rm h}32^{\rm m}22~\hbox{$.\!\!^{\rm s}$ }5$ - $27\degr46'23\hbox{$.\!\!^{\prime\prime}$ }5$ , J2000) and the Hubble Ultra Deep (square, centered at $03^{\rm h}32^{\rm m}39~\hbox{$.\!\!^{\rm s}$ }0$ - $27\degr47'29\hbox{$.\!\!^{\prime\prime}$ }1$ ) fields in the CDFS region, superimposed on the GOODS HST/ACS z-band mosaic.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{2434fg02.ps} \par\end{figure}$ Figure 2: The redshift distribution of the K20 spectroscopic catalogue for the whole extragalactic sample (empty histogram), the galaxies with "secure'' redshifts (zq=1; light gray histogram) and the type 1 AGNs (dark gray histogram).
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{2434fg03.ps} \par\end{figure}$ Figure 3: Redshift measurement completeness in the K20 survey. The fractions as a function of magnitude of the observed targets (light gray histogram) and of the objects with a redshift measurement (dark gray histogram) are shown both in the R band ( top panel) and K band ( bottom panel). The total number of sources in each magnitude bin is labeled along the top. The overall redshift measurement completeness is 92%, whilst redshifts are measured for 95% of the observed objects.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{2434fg04.ps} \end{figure}$ Figure 4: Rest-frame measurement distributions of the main spectral features: [O II] $\lambda$ 3727 EW ( top left panel; 347 measurements), [O III] $\lambda$ 5007 EW ( bottom left; 122), H $\beta$ EW ( top middle; 148), H $\alpha$ +[N II] $\lambda \lambda$ 6548, 6583 EW ( bottom middle; 63), D4000 ( top right; 426) and our UV color index ( bottom right; 349).
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{2434fg05.eps} \end{figure}$ Figure 5: The rest-frame equivalent width of the [O II] $\lambda$ 3727 line plotted against the signal-to-noise ratio ( S/N) of the continuum close to the line. The dotted line is the EW detection limit curve as estimated by Eq. (2), representing a good lower envelope of the data.
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In the text

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{2434fg06.eps} \end{figure}$ Figure 6: Relationship between the equivalent widths of the [O II] $\lambda$ 3727 line and H $\alpha$ +[N II] $\lambda \lambda$ 6548, 6583 complex for the K20 survey. The solid line shows the correlation found using our data, while the other lines represent the relationships found in the literature [ dotted line, local data (Kennicutt 1992, K92); dashed line, Stromlo-APM Survey (Tresse et al. 1999); dash-dotted line, Canada-France Redshift Survey (Tresse et al. 1996)].
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2434fg07.eps} \end{figure}$ Figure 7: D4000 vs. equivalent width of the [O II] $\lambda$ 3727 for the K20 galaxy sample. The different symbols refer to the preliminary, visual classification: filled circles are type-1 AGN, empty circles are early-type passive galaxies (class 1), crosses are red continuum emission-line galaxies (intermediate) and empty triangles are blue emission-line galaxies (class 2).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2434fg08.eps} \end{figure}$ Figure 8: Our UV color index vs. equivalent width of the [O II] $\lambda$ 3727 for the K20 galaxy sample. The different symbols refer to the preliminary, visual classification and are the same as in Fig. 7.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=14.6cm,clip]{2434fg09.eps} \end{figure}$ Figure 9: Composite spectra of the three main galaxy classes with the identification of the main absorption and emission lines. From bottom to top: early-type, intermediate and blue emission-line galaxy classes. The flux is per unit wavelength ( $F_\lambda$ ), and normalization is arbitrary. All the composite spectra can be retrieved at the following site: http://www.arcetri.astro.it/~k20/
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{2434fg10.eps} \end{figure}$ Figure 10: Normalized distributions of the absolute magnitude computed in the rest frame J-band (M_J) for the different spectroscopic classes: the solid histogram is for blue emission-line galaxies, the dashed histogram for passive early-type galaxies and the dash-dotted histogram for red continuum emission-line galaxies.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=16cm,clip]{2434fg11.eps} \end{figure}$ Figure 11: Composite spectra of the early-type galaxies divided in three redshift bins. From bottom to top: the composite of 18 low-z ( 0 < z < 0.6) galaxies, the composite of 49 intermediate-z ( 0.6 < z < 0.75) galaxies and the composite of 26 high-z ( 0.75 < z < 1.25) galaxies. Almost all the galaxies included in the intermediate-z sample belong to the two overdensities present in the K20 survey area. The flux normalization is arbitrary and the spectra are offset for clarity. The upper and lower panels also show, with the same scale, the difference spectra between the intermediate-redshift range composite and, respectively, the high-z composite and the low-z composite spectra.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{2434fg12.eps} \end{figure}$ Figure 12: D4000 strengths as a function of redshift in K20 early-type composites. The galaxies in each redshift bin have been divided in two equally populated groups, according to their luminosity, and circles and triangles indicate the brighter and fainter subsamples, respectively. The dashed line indicates the D4000 value measured in the average spectrum of the whole early-type class of Fig. 9, whereas the dash-dotted line is the D4000 measured in the SDSS composite of early-type galaxies (MAIN sample, Eisenstein et al. 2003).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=15.3cm,clip]{2434fg13.eps} \end{figure}$ Figure 13: Composite spectra of the M_J<-20 blue emission-line galaxies in four redshift bins. The flux normalization is arbitrary and the spectra are shown only in the wavelength range in which more than 20 spectra contribute to the template. The apparent intensity increase of the unresolved [O II] emission line with redshift is a visual effect due to the enhancement of rest-frame spectral resolution in the high-z composites.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{2434fg01.ps} \end{figure}$	Figure 1: The K20 (rectangle, centered at $03^{\rm h}32^{\rm m}22~\hbox{$.\!\!^{\rm s}$ }5$ - $27\degr46'23\hbox{$.\!\!^{\prime\prime}$ }5$ , J2000) and the Hubble Ultra Deep (square, centered at $03^{\rm h}32^{\rm m}39~\hbox{$.\!\!^{\rm s}$ }0$ - $27\degr47'29\hbox{$.\!\!^{\prime\prime}$ }1$ ) fields in the CDFS region, superimposed on the GOODS HST/ACS z-band mosaic.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{2434fg02.ps} \par\end{figure}$	Figure 2: The redshift distribution of the K20 spectroscopic catalogue for the whole extragalactic sample (empty histogram), the galaxies with "secure'' redshifts (zq=1; light gray histogram) and the type 1 AGNs (dark gray histogram).
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$\begin{figure} \par\includegraphics[width=14cm,clip]{2434fg04.ps} \end{figure}$	Figure 4: Rest-frame measurement distributions of the main spectral features: [O `II`] $\lambda$ 3727 EW ( top left panel; 347 measurements), [O `III`] $\lambda$ 5007 EW ( bottom left; 122), H $\beta$ EW ( top middle; 148), H $\alpha$ +[N `II`] $\lambda \lambda$ 6548, 6583 EW ( bottom middle; 63), D4000 ( top right; 426) and our UV color index ( bottom right; 349).
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$\begin{figure} \par\includegraphics[width=8.4cm,clip]{2434fg05.eps} \end{figure}$	Figure 5: The rest-frame equivalent width of the [O `II`] $\lambda$ 3727 line plotted against the signal-to-noise ratio ( S/N) of the continuum close to the line. The dotted line is the EW detection limit curve as estimated by Eq. (2), representing a good lower envelope of the data.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2434fg07.eps} \end{figure}$	Figure 7: D4000 vs. equivalent width of the [O `II`] $\lambda$ 3727 for the K20 galaxy sample. The different symbols refer to the preliminary, visual classification: filled circles are type-1 AGN, empty circles are early-type passive galaxies (class 1), crosses are red continuum emission-line galaxies (intermediate) and empty triangles are blue emission-line galaxies (class 2).
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2434fg08.eps} \end{figure}$	Figure 8: Our UV color index vs. equivalent width of the [O `II`] $\lambda$ 3727 for the K20 galaxy sample. The different symbols refer to the preliminary, visual classification and are the same as in Fig. 7.
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$\begin{figure} \par\includegraphics[angle=-90,width=14.6cm,clip]{2434fg09.eps} \end{figure}$	Figure 9: Composite spectra of the three main galaxy classes with the identification of the main absorption and emission lines. From bottom to top: early-type, intermediate and blue emission-line galaxy classes. The flux is per unit wavelength ( $F_\lambda$ ), and normalization is arbitrary. All the composite spectra can be retrieved at the following site: http://www.arcetri.astro.it/~k20/
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{2434fg10.eps} \end{figure}$	Figure 10: Normalized distributions of the absolute magnitude computed in the rest frame J-band (M_J) for the different spectroscopic classes: the solid histogram is for blue emission-line galaxies, the dashed histogram for passive early-type galaxies and the dash-dotted histogram for red continuum emission-line galaxies.
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