All Figures

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{7778fig1.eps} \end{figure}$ Figure 1: Spectroscopic redshift distribution of the 99 optical counterparts in our sample. The solid histogram refers to the whole sample, the long-dashed histogram refers to type 2 AGN and the dotted histogram refers to type 1 AGN.
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In the text

$\begin{figure} \par\includegraphics[width=7.35cm,clip]{7778fig2.eps} \end{figure}$ Figure 2: Column density distribution (galactic+intrinsic component) for the whole sample.
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In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{7778fig3.eps} \end{figure}$ Figure 3: Distribution of the photon indices that have been fitted for the X-ray sources classified as type I.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{7778fig4.eps} \end{figure}$ Figure 4: Column density distribution (galactic+intrinsic component) for type 1 AGN (solid histogram) and for type 2 AGN (long dashed histogram).
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{7778fig5.ps} \end{figure}$ Figure 5: The average value of the r coefficient over 100 000 simulations as a function of the standard deviation $\sigma$ of the assumed Gaussian distribution of the logarithm of the column density in the optical. The error bars for the r value correspond to 1 $\sigma$ . The solid line corresponds to the value r=0.275 that we obtain for our sample of 99 X-ray sources.
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In the text

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{7778fig6.eps} \end{figure}$ Figure 6: Column density distribution (galactic+intrinsic component) as a function of the absorbed [2-10] keV flux for the 99 X-ray sources. Squares are X-ray sources classified as type I while triangles correspond to X-ray sources classified as type II. Filled symbols are the sources for which the X-ray and the optical classifications do not match. The error bars correspond to the 95% confidence interval. Data points without error bars correspond to sources for which the column density has been fixed to the galactic value. These column densities are consistent with the galactic value and the presence of absorption in the relevant X-ray spectra is at least rejected at the 95% level. The horizontal line corresponds to the dividing line between type I X-ray sources (for which $N_{{\rm H}}$ < 10²² cm^-2) and type II X-ray sources ( $N_{{\rm H}}$ > 10²² cm^-2).
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In the text

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{7778fig7.ps} \end{figure}$ Figure 7: Column density (galactic+intrinsic component) as a function of the 2-10 keV intrinsic rest-frame luminosity. Squares are X-ray sources classified as type I while triangles are those classified as type II. Filled symbols are the sources for which the X-ray and the optical classifications do not match. The solid lines mark the region where type II QSOs should be found.
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In the text

$\begin{figure} \par\mbox{\includegraphics[angle=270,width=7.3cm,clip]{7778fig8a.... ...space*{0.6cm} \includegraphics[width=8.2cm,clip]{7778fig8b.ps} } \end{figure}$ Figure 8: MOS1 MOS2 (the two lower functions) and pn (upper one) X-ray spectra of a source which is only showing mild X-ray absorption with $N_{{\rm H}}^{{\rm int}}$ = 2.5 $\times$ 10²¹ cm^-2. The crosses represent the data points and the solid lines represent the folded model simultaneously fitted to the data of the 3 detectors ( left). The optical counterpart has been identified as a Seyfert 2 lying at a redshift z=0.207. We clearly observe the [OIII] lines around 6000 $\AA$ ( right). This is source #53 in Table 4.
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In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{7778fig9.eps} \end{figure}$ Figure 9: Distribution of the photon index for type I X-ray sources which are classified as type 1 (solid histogram) and as type 2 (long dashed histogram).
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7778fig10.eps} \end{figure}$ Figure 10: 2-10 keV intrinsic rest-frame luminosities as a function of redshift for our sample of X-ray sources. Squares are X-ray sources classified as type I while triangles are those classified as type II. Filled symbols are the sources for which the X-ray and the optical classifications do not match. The solid line is showing the 2-10 keV luminosity as a function of redshift for a 2-10 keV limiting flux of 8 $\times$ 10^-15 erg s^-1 cm^-2.
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In the text

$\begin{figure} \par\includegraphics[width=7.35cm,clip]{7778fig11.eps} \end{figure}$ Figure 11: X-ray to optical ratio (2-10 keV band vs. R band) as a function of X-ray flux for the 94 X-ray sources in our sample for which an R band magnitude is available. Diagonal dotted lines indicate loci of constant R magnitude while horizontal solid lines mark the boundary lines of the region of canonical AGN. The symbol convention is the same as for Fig. 10.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{7778fig12.eps} \end{figure}$ Figure 12: X-ray to optical ratio (2-10 keV band vs. R band) as a function of the deabsorbed, intrinsic 2-10 keV luminosity for the type I objects. Some of them are only presenting narrow emission lines (filled squares). The type I that show broad and obvious emission lines in their optical spectra are divided into two categories: those which lie at z<0.8 (empty squares) and those at z>0.8 (stars). The solid line represents the minimum $\chi ^{2}$ fit between log ( $F_{{\rm x}}/F_{{\rm opt}}$ ) and log L_2-10 for our data. The short dashed line represents the best linear regression for type 2 AGN, obtained using the data of Fiore et al. (2003), and the long dashed line is from the data of Treister et al. (2005).
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In the text

$\begin{figure} \par\includegraphics[height=5.7cm,width=5.9cm,clip]{7778fig13a.ep... ...*{2mm} \includegraphics[height=5.8cm,width=6cm,clip]{7778fig13b.eps}\end{figure}$ Figure 13: Diagnostic diagrams based on line ratios for our subsample of narrow line AGN with no absorption in the X-rays (filled squares) and with absorption in the X-rays (empty triangles). 6 of them for which the H $\alpha$ emission line has been observed, are plotted on the left panel and the other ones are plotted on the right panel. The solid lines from Kewley et al. (2006) ( left) and from Lamareille et al. (2004) ( right) indicate the separation between star forming galaxies and AGN, the star forming galaxies being below the line and AGN (Seyfert+LINER) above. The error bars have been estimated assuming a 5% uncertainty for the derived intensities.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7778fig14a.eps}\hspace*{3.6c... ...*{3.6cm} \includegraphics[angle=270,width=7.1cm,clip]{7778fig14d.ps}\end{figure}$ Figure 14: 2dF spectra of two absorbed X-ray sources which only present narrow emission lines in their optical spectra ( upper panel). These are sources #84 and #66 in Table 4, respectively. They have been classified as star forming galaxies, based on the line ratios inferred from their optical spectra. The lower panel show the optical spectra of the corresponding objects, obtained with the SALT. Both have been observed with the PG0300 grism ( $R\sim 400$ ). The SALT optical spectra are not flux calibrated.
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In the text

$\begin{figure} \par\mbox{\includegraphics[angle=270,width=8.2cm,clip]{7778fig15a.ps}\hspace*{3mm} \includegraphics[width=9cm,clip]{7778fig15b.ps} } \end{figure}$ Figure 15: MOS1 MOS2 (the two lower functions) and pn (upper one) X-ray spectra of a source which is showing strong X-ray absorption with $N_{{\rm H}}^{{\rm int}}$ = 4 $\times$ 10²² cm^-2. The crosses represent the data points and the solid line represent the folded model simultaneously fitted to the data of the 3 detectors ( left). The optical counterpart has been identified as a BLAGN lying at a redshift z=2.66 ( right). This is source #20 in Table 4.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{7778fig16.ps} \end{figure}$ Figure 16: The 3 XBONG candidates. Each of these 3 XBONG lacks emission lines, except for [OII] in source #72. This source presents strong absorption in the X-rays ( $N_{{\rm H}}^{{\rm int}}$ = 3.86 $\times$ 10²² cm^-2).
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In the text

$\begin{figure} \par\includegraphics[width=16.1cm,clip]{7778figa1.eps} \end{figure}$ Figure A.1: The layout of the 51 X-ray pointings of the XMM-LSS survey is such that most adjacent pointings overlap beyond 10 arcmin from their respective optical axis centers. The filled squares correspond to the 99 spectroscopically identified X-ray sources for this analysis, while the empty triangles correspond to the remaining 513 X-ray sources. Finally, the two large overlapping circles correspond to the two 2dF fields used in the spectral identification process.

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{7778figa2a.eps}\hspace*{0.5cm} \includegraphics[width=8cm,clip]{7778figa2b.eps} \end{figure}$ Figure A.2: Left panel: normalized 2-10 keV band flux distribution for the 513 still optically unidentified X-ray sources (solid line) compared to the distribution of the sample of 99 spectroscopically selected X-ray point like sources (long dashed line). Right panel: normalized hardness ratio distribution for the 513 still optically unidentified X-ray sources (solid line) compared to that of the sample of 99 optically selected X-ray point like sources (long dashed line).

In the text

$\begin{figure} \par\includegraphics[width=7.85cm,clip]{7778figa3a.eps}\hspace*{0.5cm} \includegraphics[width=7.85cm,clip]{7778figa3b.eps} \end{figure}$ Figure A.3: Left panel: histogram of the distribution of the separation between each X-ray source and its optical counterpart, for the 99 spectroscopically identified X-ray sources. Right panel: R band magnitude distribution of the 94 optical counterparts of our sample of X-ray sources for which an R band magnitude is available. For most of the objects, the magnitude is red magnitude from UKST plate scans, while the others are R magnitudes from the VVDS.

In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{7778fig1.eps} \end{figure}$	Figure 1: Spectroscopic redshift distribution of the 99 optical counterparts in our sample. The solid histogram refers to the whole sample, the long-dashed histogram refers to type 2 AGN and the dotted histogram refers to type 1 AGN.
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$\begin{figure} \par\includegraphics[width=7.35cm,clip]{7778fig2.eps} \end{figure}$	Figure 2: Column density distribution (galactic+intrinsic component) for the whole sample.
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$\begin{figure} \par\includegraphics[width=7.3cm,clip]{7778fig3.eps} \end{figure}$	Figure 3: Distribution of the photon indices that have been fitted for the X-ray sources classified as type I.
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{7778fig4.eps} \end{figure}$	Figure 4: Column density distribution (galactic+intrinsic component) for type 1 AGN (solid histogram) and for type 2 AGN (long dashed histogram).
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$\begin{figure} \par\includegraphics[width=6.8cm,clip]{7778fig5.ps} \end{figure}$	Figure 5: The average value of the r coefficient over 100 000 simulations as a function of the standard deviation $\sigma$ of the assumed Gaussian distribution of the logarithm of the column density in the optical. The error bars for the r value correspond to 1 $\sigma$ . The solid line corresponds to the value r=0.275 that we obtain for our sample of 99 X-ray sources.
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$\begin{figure} \par\includegraphics[width=7.1cm,clip]{7778fig7.ps} \end{figure}$	Figure 7: Column density (galactic+intrinsic component) as a function of the 2-10 keV intrinsic rest-frame luminosity. Squares are X-ray sources classified as type I while triangles are those classified as type II. Filled symbols are the sources for which the X-ray and the optical classifications do not match. The solid lines mark the region where type II QSOs should be found.
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$\begin{figure} \par\includegraphics[width=7.3cm,clip]{7778fig9.eps} \end{figure}$	Figure 9: Distribution of the photon index for type I X-ray sources which are classified as type 1 (solid histogram) and as type 2 (long dashed histogram).
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$\begin{figure} \par\includegraphics[width=7.35cm,clip]{7778fig11.eps} \end{figure}$	Figure 11: X-ray to optical ratio (2-10 keV band vs. R band) as a function of X-ray flux for the 94 X-ray sources in our sample for which an R band magnitude is available. Diagonal dotted lines indicate loci of constant R magnitude while horizontal solid lines mark the boundary lines of the region of canonical AGN. The symbol convention is the same as for Fig. 10.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{7778fig16.ps} \end{figure}$	Figure 16: The 3 XBONG candidates. Each of these 3 XBONG lacks emission lines, except for [OII] in source #72. This source presents strong absorption in the X-rays ( $N_{{\rm H}}^{{\rm int}}$ = 3.86 $\times$ 10²² cm^-2).
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