\begin{table}%t6
\caption{Variation of the log~$L_{\scriptsize\ha} - \log~\rm\sigma_{nt}$ envelope slope with the 
selected bin width. Each value and its error correspond respectively, to the median and standard 
deviation of the slopes for different bin starting points in~log~$L_{\scriptsize\ha}$.}\label{tabbin}
%\centering
\par
\begin{tabular}{ccc|cc|cc}
\hline
\hline
Bin width      & \multicolumn{2}{c}{NGC~1530}  & \multicolumn{2}{c}{NGC~6951} & \multicolumn{2}{c}{NGC~3359}   \\
\hline
    dex     & Frac of $L_{\scriptsize \ha}$ & Total $L_{\scriptsize \ha}$ & Frac of $L_{\scriptsize \ha}$ & Total $L_{\scriptsize \ha}$ & Frac of $L_{\scriptsize \ha}$ & Total $L_{\scriptsize \ha}$ \\ 
\hline
  0.10   & $2.4\pm0.2$ & $1.9\pm0.3$ & $0.8\pm0.2$& $0.8\pm0.2$& $1.6\pm0.3$& $1.1\pm0.3$ \\
  0.15   & $2.4\pm0.2$ & $2.0\pm0.2$ & $1.2\pm0.4$& $1.2\pm0.4$& $1.5\pm0.2$& $1.4\pm0.3$ \\
  0.20   & $2.4\pm0.2$ & $1.9\pm0.1$ & $1.6\pm1.9$& $1.6\pm1.9$& $1.6\pm0.2$& $1.4\pm0.3$ \\
\hline
\end{tabular}
\end{table}