\begin{table}%t4
\begin{minipage}[t]{\columnwidth}
\caption{Main parameters derived from the radio
continuum data at 3.6~cm for an assumed distance $d$ of 5~kpc.}
\label{continuo} 
%%\centering
\par
\renewcommand{\footnoterule}{}
\begin{tabular}{l c}
\hline \hline
Parameter & Value \\ 
\hline 
Flux density $S_{3.6 ~\rm cm}$ & 205 $\pm$ 10 mJy \\ 
Emission measure $EM$ &  $1.3\times10^4$ pc~cm$^{-6}$ \\ 
Angular semi-axis & $\sim  $55\as \\  
Linear radius & $\sim$1.3 pc \\   
rms electron density
$n_{\rm e}$ ($f$ = 1.0) &  140 \\ 
Ionized mass $M_i$\footnote{Including a factor of 1.27 for singly ionized He}
 ($f$ = 1.0) &  22.5 \msun \\ 
\hline 
Filling factor $f$ & 0.05--0.15 \\ 
Electron density $n_{\rm e}$ &  630--360~cm$^{-3}$ \\ 
Ionized mass $M_i$ \footnote{Including a factor of 1.27 for singly ionized He}&  5--9 \msun \\ 
\hline
\end{tabular}
\end{minipage}
\end{table}