All Figures

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{5720f1.eps} %\end{figure}$ Figure 1: ESO/WFI coverage for Fornax dSph. The inner shell-like feature detected by Coleman et al. (2004) is located at $\xi \sim 0.12$ , $\eta \sim -0.20$ and elliptical radius of 0.33 deg. The circles indicate the location of Fornax globular clusters and the ellipse shows Fornax tidal radius (ellipse parameters derived in this work, see Table 2). The North is at the top, the East on the left-hand side. The physical scale at the distance of the Fornax dSph is 1 deg = 2.4 kpc.
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In the text

$\begin{figure} \par\includegraphics[width=4.2cm,clip]{5720f2a.eps}\includegraphi... ...m,clip]{5720f2c.eps}\includegraphics[width=4.2cm,clip]{5720f2d.eps} \end{figure}$ Figure 2: The variation with radius of the central position (x and y coordinate, a) and b) respectively), c) ellipticity and d) position angle for the entire stellar population of Fornax, from ESO/WFI imaging data. The variation of the central position is with respect to the value listed in Mateo (1998). We find that the centre is at $\alpha =2^{\rm h} 39^{\rm m} 52^{\rm s}$ and $\delta = -34^{\circ } 30' 49''$ , west ( $-1.5' \pm 0.3'$ ) and south ( $-3.8' \pm 0.2'$ ) with respect to the values listed in Mateo (1998).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5720f3.eps} \end{figure}$ Figure 3: The surface density profile for Fornax dSph galaxy with overlaid best-fitting King, Sersic, exponential and Plummer models (solid, dashed, dotted, dash-dot lines, respectively). The Galactic stellar contamination, $0.78\pm 0.02$ stars arcmin^-2 calculated from a weighted average of the points beyond 1.13 deg (68'), has been subtracted from each point. The error bars are obtained by summing in quadrature the errors from Poisson statistics and the error in Galactic stellar contamination. Our best fit to the data is a Sersic profile with Sersic radius, $R_{\rm S}= 17.3 \pm 0.2$ arcmin and m= 0.71. The best-fitting parameters for the different models are summarized in Table 3.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5720f4a.eps}\par\vspace*{3mm} \includegraphics[width=8cm,clip]{5720f4b.eps} \end{figure}$ Figure 4: CMD for objects classified as stellar from our ESO/WFI imaging covering the whole extent of the Fornax dSph. The boxes in panel b) indicate the regions we used to select different stellar populations (MS: main sequence; BL: Blue Loop; FOR: foreground; BHB: Blue Horizontal Branch; RRLy: RRLyrae; RHB: Red Horizontal Branch; B-RGB: Blue-Red Giant Branch; R-RGB: Red-Red Giant Branch; AGBb: AGB bump; RC: Red Clump).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5720f5.eps} \end{figure}$ Figure 5: The Hess diagram for Fornax dSph CMD from ESO/WFI imaging, where the structures, and their relative intensity, in the different regions of the CMD are visible. Each cell is $\Delta (V-I) \times \Delta V = 0.01 \times 0.05$ . A darker tone represents an higher density of stars; zero-density is set to white. This allows us to see the structure in the Red Clump and Red Horizontal Branch.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{5720f6a.eps}\par\includegrap... ...clip]{5720f6b.eps}\par\includegraphics[width=7cm,clip]{5720f6c.eps} \end{figure}$ Figure 6: ESO/WFI CMDs for the Fornax dSph at radii r< 0.4 a), 0.4 <r< 0.7 b), r> 0.7 deg c). We have normalized the number of stars in the 3 panels to allow a more meaningful comparison. Note the change in stellar population as function of radius: the young population (main sequence and Blue Loop stars) is absent beyond r>0.4 deg, whilst the ancient population becomes more dominant, as can be seen for example from the more visible BHB at r>0.4 deg, the bluer average colour of the RGB, and the less extended RC in V mag.
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In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{5720f7a.eps}\par\vspace*{1... ...\par\vspace*{1.5mm} \includegraphics[width=7.3cm,clip]{5720f7c.eps} \end{figure}$ Figure 7: Spatial distribution of BHB, RHB and RC stars in the Fornax dSph as selected from the CMD shown in Fig. 4b. The RC stars show a more concentrated and less extended distribution than RHB and BHB stars. The number of RC stars has been normalised to the number of RHB stars.
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In the text

$\begin{figure} \par\includegraphics[width=4cm,clip]{5720f8a.eps}\includegraphics[width=4cm,clip]{5720f8b.eps} \end{figure}$ Figure 8: Spatial distribution of Blue RGB and Red RGB stars in the Fornax dSph (as selected from the CMD shown in Fig. 4b).
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{5720f9a.eps}\par\includegraphics[width=9cm,clip]{5720f9b.eps} \end{figure}$ Figure 9: Surface number density ( top) and fraction of stars within elliptical radius r ( bottom) of ancient stellar populations in the Fornax dSph (solid line: RHB stars; dotted line: BHB stars; dash-dot-dot line: RRLyrae stars; dashed line: B-RGB stars). The surface number density has been Galactic stellar contamination subtracted. Note that all the ancient stars, even if found at different stages of stellar evolution, display a similar spatial trend with radius. In the bottom panel we show for comparison the fraction of stars within elliptical radius r for RC stars (long dashed line), representative of intermediate age stars: note the more extended and less concentrated spatial distribution of ancient stars with respect to intermediate age stars.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{5720f10a.eps}\par\vspace*{1.5mm} \includegraphics[width=8.6cm,clip]{5720f10b.eps} \end{figure}$ Figure 10: As in Fig. 9 but for intermediate age stellar populations (solid line: RC stars; dotted line: R-RGB stars; dash-dot-dot line: AGB bump stars). All the intermediate age populations display a similar spatial trend with radius. In the bottom panel we show for comparison the fraction of stars within elliptical radius r for RHB stars (long dashed line), representative of ancient stars, as in Fig. 9: note the more extended and less concentrated spatial distribution of ancient stars with respect to intermediate age stars.
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In the text

$\begin{figure} \par\includegraphics[width=7.25cm,clip]{5720f11a.eps}\par\include... ...{5720f11b.eps}\par\includegraphics[width=7.25cm,clip]{5720f11c.eps} \end{figure}$ Figure 11: Spatial distribution of main sequence a) and Blue Loop b) stars in the Fornax dSph (as selected from the CMD shown in Fig. 4b) and c) the foreground contamination in the Blue Loop distribution as from a CMD-selected sample of foreground stars to match the Blue Loop contamination density. Note the asymmetric distribution of MS stars in a), elongated in the E-W direction and tilted by $\sim$ $40^{\circ }$ with respect to the main body of Fornax dSph. The inner shell-like feature detected by Coleman et al. (2004) is located at $\xi \sim 0.12$ , $\eta \sim -0.20$ and elliptical radius of 0.33. This is also the position of one of the two fields observed by Olszewski et al. (2006).
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{5720f12.eps} \end{figure}$ Figure 12: CMD for stars within 0.4 degree of the centre of the Fornax dSph; the box shows the selection region for the Blue Loop stars. The colours and magnitudes of the Blue Loop stars are consistent with theoretical Padua isochrones (Girardi et al. 2000) of metallicity Z=0.004 ( $\rm [Fe/H]\sim -0.7$ ) and age 0.4, 0.5, 0.6, 0.7 Gyr ( from top to bottom). The stars forming the BL feature have mass in the range 2.3-2.8 $M_{\odot }$ .
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{5720f13.eps} \end{figure}$ Figure 13: Location of the observed FLAMES fields and targets (with S/N per Å > 10 and error in velocity <5 km s^-1) in the Fornax dSph (squares: probable members; crosses: probable non-members). The black filled circles show the location of Fornax globular clusters, the black small ellipse shows the location of the "shell-like'' feature detected by Coleman et al. 2004, and the dashed circles indicate the observed FLAMES fields. The tidal radius is from this work.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{5720f14.eps} \end{figure}$ Figure 14: Histogram of velocities for the observed VLT/FLAMES targets in the Fornax dSph which passed our S/N and velocity error criteria (641 stars).
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In the text

$\begin{figure} \par\includegraphics[width=17.5cm,clip]{5720f15.eps} \end{figure}$ Figure 15: Heliocentric velocity with elliptical radius from VLT/FLAMES spectroscopic observations of individual RGB stars in the Fornax dSph. We plotted all the stars which satisfy our selection criteria (S/N per Å > 10 and velocity error <5 km s^-1). The dashed line is the systemic velocity, $V_{\rm sys}= 54.1$ km s^-1, and the dotted lines encompass the 2.5 $\sigma$ region of our kinematic selection. The squares show Fornax velocity members (filled: metal rich members, $\rm [Fe/H]>-1.3$ ; open: metal poor members, $\rm [Fe/H]<-1.3$ ), and the crosses foreground contamination.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5720f16.eps} \end{figure}$ Figure 16: Location on the CMD of the observed FLAMES targets for Fornax dSph (squares: probable members; crosses: probable non-members). The boundaries of our target selection region closely follow the location of the targets. The asterisks indicates stars selected as velocity members falling in unusual position in the CMD; they are likely to be Galactic foreground contamination (see Fig. 17).
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In the text

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{5720f17.eps} \end{figure}$ Figure 17: Metallicity versus heliocentric velocity for the observed FLAMES targets with S/N per $\rm \AA >10$ , and error in velocity <5 km s^-1. The dotted lines show the region of our kinematic selection. Note that Galactic contaminants predominantly cluster between $-1.8<\rm [Fe/H]<-1.0$ (horizontal lines). The asterisks show the Fornax velocity members present in unusual position in the CMD (see Fig. 16).
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In the text

$\begin{figure} \par\includegraphics[width=9cm,clip]{5720f18.eps} \end{figure}$ Figure 18: Metallicity distribution with elliptical radius for the Fornax dSph. Note the trend of decreasing metallicity with radius and the absence of very metal poor stars (dotted line indicates $\rm [Fe/H] = -2.8$ ).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5720f19.eps} \end{figure}$ Figure 19: Histogram of metallicity measurements for individual RGB stars in the Fornax dSph (solid line: all velocity members; dotted line: velocity members within r< 0.4 deg from the centre; dashed line: velocity members between 0.4<r<0.7 deg from the centre; dashed-dotted line: velocity members at r>0.7 deg from the centre).
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In the text

$\begin{figure} \par\includegraphics[width=16cm,clip]{5720f20.eps} \end{figure}$ Figure 20: Velocity histograms for 3 different distance bins for metal rich (dashed) and metal poor (dotted) stars in the Fornax dSph. The "metal rich'' stars display a colder kinematics than the "metal poor'' stars (see Table 3). Note the flat/double-peaked velocity distribution of MP stars in the inner bin.
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In the text

$\begin{figure} \par\includegraphics[width=6.7cm,clip]{5720f21.eps} \end{figure}$ Figure 21: The squares with errorbars show the cumulative velocity distribution for MP stars ( $\rm [Fe/H]<-1.3$ ) in the inner distance bin in the Fornax dSph (see Fig. 20). The dotted line is the cumulative distribution of a Gaussian with mean velocity and dispersion as measured for MR stars in the inner distance bin and the same number of stars as in the MP component within r< 0.4 deg (solid line with errorbars). A KS-test gives a probability of 0.7% for MP and MR stars in the inner bin to be drawn from the same distribution.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5720f22a.eps}\par\includegra... ...ip]{5720f22b.eps}\par\includegraphics[width=8cm,clip]{5720f22c.eps} \end{figure}$ Figure 22: The comparison between measured metallicities and colours of Fornax stars (asterisks) with the theoretical isochrones (lines) for the metallicity of the stars. a) Stars with $\rm [Fe/H]=-1.7\pm 0.1$ and two YY isochrones of $\rm [Fe/H]=-1.7$ and age 2 and 13 Gyr (from left to right). b) Stars with $\rm [Fe/H]=-1\pm 0.1$ and two YY isochrones of $\rm [Fe/H]=-1$ and age 2 and 5 Gyr (from left to right). c) Stars with $\rm [Fe/H]=-0.7\pm 0.1$ and two YY isochrones of $\rm [Fe/H]=-0.7$ and age 1 and 2 Gyr (from left to right).
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In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{5720f23.eps} \end{figure}$ Figure 23: Ages and errorbars derived from isochrones fitting of the VLT/FLAMES spectroscopic sample of RGB stars in Fornax dSph. The lines shows the average value of [Fe/H] as a function of age assuming [ $\alpha$ /Fe] = 0 (solid), [ $\alpha$ /Fe] = 0.3 (dotted), and [ $\alpha$ /Fe] decreasing with [Fe/H] (dashed). The stars plotted as asterisks and diamonds were excluded from the analysis because they fell outside the age range of the isochrones for the considered metallicity.
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In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{5720f7a.eps}\par\vspace{1... ...\par\vspace{1.5mm} \includegraphics[width=7.3cm,clip]{5720f7c.eps} \end{figure}$	Figure 7: Spatial distribution of BHB, RHB and RC stars in the Fornax dSph as selected from the CMD shown in Fig. 4b. The RC stars show a more concentrated and less extended distribution than RHB and BHB stars. The number of RC stars has been normalised to the number of RHB stars.
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$\begin{figure} \par\includegraphics[width=4cm,clip]{5720f8a.eps}\includegraphics[width=4cm,clip]{5720f8b.eps} \end{figure}$	Figure 8: Spatial distribution of Blue RGB and Red RGB stars in the Fornax dSph (as selected from the CMD shown in Fig. 4b).
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$\begin{figure} \par\includegraphics[width=7.6cm,clip]{5720f14.eps} \end{figure}$	Figure 14: Histogram of velocities for the observed VLT/FLAMES targets in the Fornax dSph which passed our S/N and velocity error criteria (641 stars).
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$\begin{figure} \par\includegraphics[width=9cm,clip]{5720f18.eps} \end{figure}$	Figure 18: Metallicity distribution with elliptical radius for the Fornax dSph. Note the trend of decreasing metallicity with radius and the absence of very metal poor stars (dotted line indicates $\rm [Fe/H] = -2.8$ ).
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5720f19.eps} \end{figure}$	Figure 19: Histogram of metallicity measurements for individual RGB stars in the Fornax dSph (solid line: all velocity members; dotted line: velocity members within r< 0.4 deg from the centre; dashed line: velocity members between 0.4<r<0.7 deg from the centre; dashed-dotted line: velocity members at r>0.7 deg from the centre).
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$\begin{figure} \par\includegraphics[width=16cm,clip]{5720f20.eps} \end{figure}$	Figure 20: Velocity histograms for 3 different distance bins for metal rich (dashed) and metal poor (dotted) stars in the Fornax dSph. The "metal rich'' stars display a colder kinematics than the "metal poor'' stars (see Table 3). Note the flat/double-peaked velocity distribution of MP stars in the inner bin.
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