\begin{table}%t1
\par
\caption{Compiled data for the different radio continuum surveys.
\label{tab_surveys}}
%\centerline
 {\begin{tabular}{llllll}
\hline
\hline
Survey  &  Frequency & Resol. & 5-$\sigma$ &  $N_{\rm{CIG}}^{1}$ & $N_{\rm{det}}^{1}$  \\
    &  (MHz)    & (arcmin) & (mJy)  &  &  \\
\hline
WENSS  &  325 \& 352 &  $\sim$$  1$ & $\sim$$ 18$  & 405/278 & 49/37\\
NVSS   &  1420  &  $\sim$$  0.8$  & $\sim$$  2$ & 1050/719 &  374/311\\
FIRST  &  1420  &  $\sim $$ 0.08$ & $\sim $$ 1$ & 560/360 & 81/58\\
GB6    &  4850  &  $\sim $$ 3.5$   & $\sim $$ 18$ &  1017/691 & 32/12  \\
\hline
\end{tabular}}
\par
\smallskip
 $^{\rm 1}$  Total number of
galaxies with radio data  ($N_{\rm{CIG}}$) and with radio detection
($N_{\rm{det}}$), followed by the number of galaxies belonging to the
complete subsample of $N=719$~galaxies.
\end{table}