All Figures

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{H3888F1.eps}\end{figure}$ Figure 1: Result of Vigotti et al. (1989) on the relation between flux density and spectral index for frequencies of 408 MHz and 1465 MHz. The data are from B3 (open circles, Ficarra et al. 1985) and Benn et al. (1988) (filled circles).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,height=7.52cm,clip]{H3888F2.eps}\end{figure}$ Figure 2: The result of Steppe & Gopal-Krishna (1984) of the flux density-spectral index relation for frequency of 408 MHz (except sample g which is defined at 611 MHz) and a higher frequency which is 1.4, 2.7 or 5.0 GHz as indicated by crosses, open circles and dots, respectively.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.35cm,clip]{H3888F3.PS}\end{figure}$ Figure 3: The variation of the source fraction for FSS sources (bottom), SSS sources (top) and USS sources (middle) at 327 MHz.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{H3888F4.PS}\end{figure}$ Figure 4: Statistical results of the flux density-spectral index relation using the WENSS-NVSS catalogs.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.35cm,clip]{H3888F5.PS}\end{figure}$ Figure 5: The contour/grey scale map of the $\alpha _{\rm med}$ -S relation of WENSS-NVSS for all the 185 789 source pairs. The map is a $512 \times 512$ matrix with pixel spacings of $\Delta S{:} (10~000 - 10)/511$ mJy and $\Delta \alpha : (0.5 - (-2.5))/511$ . The maximum value is 549. Contours start at 9% of the maximum with an interval of 9%.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{H3888F6.PS}\end{figure}$ Figure 6: The $\alpha _{\rm med}$ -S relations of steep-spectrum and flat-spectrum sources (WENSS-NVSS).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{H3888F7.PS}\end{figure}$ Figure 7: Predicted $\rm\alpha _{med}$ -S relations from the model 1 proposed by Peacock & Gull (1981) (full line) and the Condon's model (dash line) with the new statistical results from this paper (marked by +).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{H3888F8.PS}\end{figure}$ Figure 8: The predicted percentage of flat-spectrum sources at 1.4 GHz (Jackson & Wall 1999) (solid line) and the statistical result (dashed line) using the WENSS and NVSS catalogs.
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In the text

$\begin{figure} \par\includegraphics[width=8.6cm,clip]{H3888F1.eps}\end{figure}$	Figure 1: Result of Vigotti et al. (1989) on the relation between flux density and spectral index for frequencies of 408 MHz and 1465 MHz. The data are from B3 (open circles, Ficarra et al. 1985) and Benn et al. (1988) (filled circles).
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.8cm,height=7.52cm,clip]{H3888F2.eps}\end{figure}$	Figure 2: The result of Steppe & Gopal-Krishna (1984) of the flux density-spectral index relation for frequency of 408 MHz (except sample g which is defined at 611 MHz) and a higher frequency which is 1.4, 2.7 or 5.0 GHz as indicated by crosses, open circles and dots, respectively.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.35cm,clip]{H3888F3.PS}\end{figure}$	Figure 3: The variation of the source fraction for FSS sources (bottom), SSS sources (top) and USS sources (middle) at 327 MHz.
Open with DEXTER

$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{H3888F4.PS}\end{figure}$	Figure 4: Statistical results of the flux density-spectral index relation using the WENSS-NVSS catalogs.
Open with DEXTER

$\begin{figure} \par\includegraphics[angle=-90,width=8.35cm,clip]{H3888F5.PS}\end{figure}$	Figure 5: The contour/grey scale map of the $\alpha _{\rm med}$ -S relation of WENSS-NVSS for all the 185 789 source pairs. The map is a $512 \times 512$ matrix with pixel spacings of $\Delta S{:} (10~000 - 10)/511$ mJy and $\Delta \alpha : (0.5 - (-2.5))/511$ . The maximum value is 549. Contours start at 9% of the maximum with an interval of 9%.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{H3888F6.PS}\end{figure}$	Figure 6: The $\alpha _{\rm med}$ -S relations of steep-spectrum and flat-spectrum sources (WENSS-NVSS).
Open with DEXTER

$\begin{figure} \par\includegraphics[angle=-90,width=8.3cm,clip]{H3888F7.PS}\end{figure}$	Figure 7: Predicted $\rm\alpha _{med}$ -S relations from the model 1 proposed by Peacock & Gull (1981) (full line) and the Condon's model (dash line) with the new statistical results from this paper (marked by +).
Open with DEXTER

$\begin{figure} \par\includegraphics[angle=-90,width=8.5cm,clip]{H3888F8.PS}\end{figure}$	Figure 8: The predicted percentage of flat-spectrum sources at 1.4 GHz (Jackson & Wall 1999) (solid line) and the statistical result (dashed line) using the WENSS and NVSS catalogs.
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