All Figures

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{Fig1a.eps}\hspace*{1.6cm} \includegraphics[width=8.8cm,clip]{Fig1b.eps}\end{figure}$ Figure 1: Left panel: $4\hbox {$^\prime $ }$ $\times$ $4\hbox {$^\prime $ }$ 2MASS $K_{\rm s}$ image of FSR 1716. Image provided by the 2MASS Image Service. The small circle indicates the central coordinates (Cols. 2 and 3 of Table 1). Right panel: $7\hbox {$^\prime $ }$ $\times$ $7\hbox {$^\prime $ }$ XDSS R image of Cz 23. North is to the top and East to the left.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{Fig2.eps}\end{figure}$ Figure 2: Stellar surface-density $\sigma (\rm stars\ arcmin^{-2})$ of FSR 1716 ( left panels) and Cz 23 ( right). The curves were computed for a mesh size of $4\hbox {$^\prime $ }$ $\times$ $4\hbox {$^\prime $ }$ , centred on the coordinates in Table 1. The observed (raw) and field-star decontaminated photometry are shown in the top and bottom panels, respectively.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig3.eps}\end{figure}$ Figure 3: 2MASS CMDs extracted from the $R<3\hbox {$^\prime $ }$ region of FSR 1716. Top panels: observed photometry with the colours $\mbox{$J$ }\times\mbox{$(J-H)$ }$ ( left) and $\mbox{$J$ }\times\mbox{$(J-K_{\rm s})$ }$ ( right). Middle: equal-area ( $19.77\hbox {$^\prime $ }<R<20\hbox {$^\prime $ }$ ) extraction of the comparison field, where the significant disk and bulge contamination can be seen. Bottom panels: decontaminated CMDs that reveal a highly reddened, relatively populous MS and a giant branch, typical of old clusters.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig4.eps}\end{figure}$ Figure 4: Same as Fig. 3 for the region $R<4\hbox {$^\prime $ }$ of Cz 23. Contamination, in this case, is less. The equal-area comparison field extraction was taken from the region $19.6\hbox {$^\prime $ }<R<20\hbox {$^\prime $ }$ . A giant clump shows up especially in the decontaminated CMDs, denoting advanced age.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig5.eps}\end{figure}$ Figure 5: Same as Fig. 3 for the $R<3\hbox {$^\prime $ }$ region of a ``test-field'' located at $1^\circ$ to the East of FSR 1716. The decontaminated CMDs ( bottom panels) contain essentially statistical noise.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig6.eps}\end{figure}$ Figure 6: Left panels: observed and decontaminated CMDs extracted from $R=4\hbox {$^\prime $ }$ comparison fields, taken at 20 $^\prime$ to each side of Cz 23. The corresponding RDPs ( right panels) exhibit mainly field-fluctuation features.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig7.eps}\end{figure}$ Figure 7: Top panels: the field-decontaminated ( $R<3\hbox {$^\prime $ }$ ) CMD morphology of FSR 1716 (empty circles) is compared to that of the $\sim$ 7 Gyr OC NGC 188 (gray circles). $\mbox{$J$ }$ $\times$ $\mbox{$(J-H)$ }$ ( left panels) and $\mbox{$J$ }$ $\times$ $\mbox{$(J-K_{\rm s})$ }$ ( right) CMDs are shown. Bottom: same as above for the $R<4\hbox {$^\prime $ }$ CMD of Cz 23 (empty circles) and M 67 (gray circles). The adopted fit (Sect. 5.3.1) for FSR 1716 corresponds to the 7 Gyr, solar-metallicity Padova isochrone, while for Cz 23, we adopted the 5 Gyr, solar-metallicity isochrone (Sect. 5.3.2). The shaded polygon overplotted in the left panels shows the colour-magnitude filter.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig8.eps}\end{figure}$ Figure 8: Age and metallicity interpretation of FSR 1716. Top-left panel: isochrones of different ages and fixed solar metallicity. Top-right: same ages but with the sub-solar metallicity $\rm [Fe/H]=-0.5$ (Z=0.006). Fits have in common a similar description of the MS. Middle panels: template fit assuming a GC-like RGB and sub-giant branch morphology for FSR 1716, with the GC NGC 6397 ( $\rm [Fe/H]=-1.95$ , Z=0.0002 - left panel), and M 4 ( $\rm [Fe/H]=-1.21$ , Z=0.0012 - right). Padova isochrones of 12 Gyr and same metallicity as the GCs are shown. Bottom panels: same as above but assuming a brighter MSTO for FSR 1716. The colour range in each panel is optimised to shown differences among the fits ( top) and enhance the relevant features ( bottom).
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig9.eps}\end{figure}$ Figure 9: Age and metallicity interpretation of Cz 23. Top panels: isochrones of different ages and fixed solar metallicity. Bottom: same ages but with the sub-solar metallicity $\rm [Fe/H]=-0.5$ (Z=0.006). Fits are required to provide a similar description of the MS.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig10.eps}\end{figure}$ Figure 10: Stellar RDPs (filled circles) of FSR 1716 ( left panels) and Cz 23 ( right). RDPs built with the observed (raw) photometry are shown in the top panels, while those built with colour-magnitude filtered photometry are in the bottom panels. Solid line: best-fit King-like profile. Horizontal shaded polygon: offset field stellar background level. Shaded regions: $1\sigma$ King fit uncertainty. The core and cluster radii are indicated. Inset of panel a): RDP of the test-field of FSR 1716. Angular scale is used.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig11.eps}\end{figure}$ Figure 11: Mass function computed for the whole region of FSR 1716 ( top panel) and Cz 23 ( bottom). The MF of FSR 1716 can be represented by the broken power-law $\phi (m)\propto m^{-(1+\chi )}$ , with $\chi =-9.4$ $\pm$ 0.6 for $m\le0.98~\mbox{$M_\odot$ }$ , and $\chi =2.3$ $\pm$ 0.4 for $0.98<m(\mbox{$M_\odot$ })<1.1$ . The MF drop begins at $m\approx0.98~\mbox{$M_\odot$ }$ , which corresponds to $\mbox{$J$ }\approx14.5$ . The MF of Cz 23 can be described by a power-law with slope $\chi =-3.1$ $\pm$ 0.5.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig12.eps}\end{figure}$ Figure 12: Relations involving OC structural and fundamental parameters. Circles: nearby OCs. Dotted circles: massive OCs (> $1000~\mbox{$M_\odot$ }$ ). Two sets of parameters are shown for FSR 1716, according to the old OC and GC solutions.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig13.eps}\end{figure}$ Figure 13: Galactic position of FSR 1716 and Cz 23 compared to the WEBDA OCs with ages younger (shaded circles) and older (filled circles) than 1 Gyr. The schematic projection of the Galaxy is seen from the North pole, with 7.2 kpc as the Suns distance to the Galactic centre. Main structures are identified.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{Fig1a.eps}\hspace*{1.6cm} \includegraphics[width=8.8cm,clip]{Fig1b.eps}\end{figure}$	Figure 1: Left panel: $4\hbox {$^\prime $ }$ $\times$ $4\hbox {$^\prime $ }$ 2MASS $K_{\rm s}$ image of FSR 1716. Image provided by the 2MASS Image Service. The small circle indicates the central coordinates (Cols. 2 and 3 of Table 1). Right panel: $7\hbox {$^\prime $ }$ $\times$ $7\hbox {$^\prime $ }$ XDSS R image of Cz 23. North is to the top and East to the left.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{Fig2.eps}\end{figure}$	Figure 2: Stellar surface-density $\sigma (\rm stars\ arcmin^{-2})$ of FSR 1716 ( left panels) and Cz 23 ( right). The curves were computed for a mesh size of $4\hbox {$^\prime $ }$ $\times$ $4\hbox {$^\prime $ }$ , centred on the coordinates in Table 1. The observed (raw) and field-star decontaminated photometry are shown in the top and bottom panels, respectively.
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$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig4.eps}\end{figure}$	Figure 4: Same as Fig. 3 for the region $R<4\hbox {$^\prime $ }$ of Cz 23. Contamination, in this case, is less. The equal-area comparison field extraction was taken from the region $19.6\hbox {$^\prime $ }<R<20\hbox {$^\prime $ }$ . A giant clump shows up especially in the decontaminated CMDs, denoting advanced age.
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$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig5.eps}\end{figure}$	Figure 5: Same as Fig. 3 for the $R<3\hbox {$^\prime $ }$ region of a ``test-field'' located at $1^\circ$ to the East of FSR 1716. The decontaminated CMDs ( bottom panels) contain essentially statistical noise.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig6.eps}\end{figure}$	Figure 6: Left panels: observed and decontaminated CMDs extracted from $R=4\hbox {$^\prime $ }$ comparison fields, taken at 20 $^\prime$ to each side of Cz 23. The corresponding RDPs ( right panels) exhibit mainly field-fluctuation features.
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$\begin{figure} \par\includegraphics[width=8.7cm,clip]{Fig9.eps}\end{figure}$	Figure 9: Age and metallicity interpretation of Cz 23. Top panels: isochrones of different ages and fixed solar metallicity. Bottom: same ages but with the sub-solar metallicity $\rm [Fe/H]=-0.5$ (Z=0.006). Fits are required to provide a similar description of the MS.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig12.eps}\end{figure}$	Figure 12: Relations involving OC structural and fundamental parameters. Circles: nearby OCs. Dotted circles: massive OCs (> $1000~\mbox{$M_\odot$ }$ ). Two sets of parameters are shown for FSR 1716, according to the old OC and GC solutions.
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$\begin{figure} \par\includegraphics[width=8.6cm,clip]{Fig13.eps}\end{figure}$	Figure 13: Galactic position of FSR 1716 and Cz 23 compared to the WEBDA OCs with ages younger (shaded circles) and older (filled circles) than 1 Gyr. The schematic projection of the Galaxy is seen from the North pole, with 7.2 kpc as the Suns distance to the Galactic centre. Main structures are identified.
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