All Figures

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{1916fig1.ps}\end{figure}$ Figure 1: Comparison between $z_{\rm spec}$ and $z_{\rm phot}$ for X-ray sources with point-like optical light profile and spectroscopic redshift measurements. A large circle on top of a symbol is for sources with r > 21. The solid line is the $z_{\rm spec}$ = $z_{\rm phot}$ locus. The dashed lines define the $\delta z = \pm 0.3$ envelope around the $z_{\rm spec}$ = $z_{\rm phot}$ line.
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In the text

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{1916fig2.ps}\end{figure}$ Figure 2: $\delta z$ against g-r colour for optically extended X-ray sources with spectroscopic redshift measurements. Our method provides reasonable photometric redshift estimates for relatively red sources (g - r>0.5). For bluer optical colours the accuracy of our method is poorer, most likely because of contamination of the optical light from the central engine.
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In the text

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{1916fig3.ps}\end{figure}$ Figure 3: Comparison between $z_{\rm spec}$ and $z_{\rm phot}$ for X-ray sources with extended optical light profile and spectroscopic redshift measurements. Filled circles are for red (g-r>0.5) and crosses are for blue (g-r<0.5) sources. The solid line is the $z_{\rm spec}$ = $z_{\rm phot}$ locus. The dashed lines define the $\delta z = \pm 0.15$ envelope around the $z_{\rm spec}$ = $z_{\rm phot}$ line.
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In the text

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{1916fig4.ps}\end{figure}$ Figure 4: Colour-colour diagram of the X-ray sources with point-like optical morphology. Open circles are for sources without $z_{\rm spec}$ , filled circles correspond to sources in the spectroscopic sub-sample. A large circle on top of a symbol is for sources with problematic photometric redshift estimates ( $\delta z > 0.3$ ). The two curves are colour-colour tracks of the HMP00 QSO templates in the redshift range 0-6 for two different values of the optical power-law spectral index, 0 and 1 for the solid and the long-dashed lines respectively. For $u-g \protect \ga 0.6$ these templates correspond to $z \protect \ga 2$ . The short-dashed horizontal and vertical lines correspond to u-g=0.6 and g-r=0.6. 7 point-like X-ray sources have colours redder than these limits. The photometric redshifts of these sources are likely to be problematic since they may have SEDs substantially different to those expected for optically selected QSOs.
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In the text

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{1916fig1.ps}\end{figure}$	Figure 1: Comparison between $z_{\rm spec}$ and $z_{\rm phot}$ for X-ray sources with point-like optical light profile and spectroscopic redshift measurements. A large circle on top of a symbol is for sources with r > 21. The solid line is the $z_{\rm spec}$ = $z_{\rm phot}$ locus. The dashed lines define the $\delta z = \pm 0.3$ envelope around the $z_{\rm spec}$ = $z_{\rm phot}$ line.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{1916fig2.ps}\end{figure}$	Figure 2: $\delta z$ against g-r colour for optically extended X-ray sources with spectroscopic redshift measurements. Our method provides reasonable photometric redshift estimates for relatively red sources (g - r>0.5). For bluer optical colours the accuracy of our method is poorer, most likely because of contamination of the optical light from the central engine.
Open with DEXTER