\begin{table}%T12
%\centering
\par
\caption{logarithm of the minimum ${\rm Fe^{+}}$ column density $\frac{N_{\rm c}}{g_{\rm c}}$
(for an excitation potential $\chi_{\rm c}=2.75~ $eV) of both components
emission line region at the different epochs studied. The first line
display (N) the narrow component region values, while the second line
displays (B) the broad component region ones. \label{Tab_column_density}}
\par
\begin{tabular}{cccc}
\hline\hline 
year&
1995&
1999&
2001\\
\hline
\par
 $\log\frac{N_{\rm c}}{g_{\rm c}}$ (N)&
$14.6\pm0.1$&
$14.9\pm0.1$&
$14.73\pm0.1$\\
%\hline 
 $\log\frac{N_{\rm c}}{g_{\rm c}}$ (B)&
$14.4\pm0.1$&
$14.5\pm0.1$&
$14.5\pm0.1$\\
\hline
\end{tabular}
\end{table}