\begin{table}%t2
      \caption{\label{tab2}Properties of clusters with and without substructure}
     %\centering
\par
         \begin{tabular}{ccccc}
            \hline\hline
 Mean  &   \multicolumn{2}{c}{$M_{r}<-20$} &  \multicolumn{2}{c}{$M_{r}<-19$}  \\
                   & Sub & No Sub & Sub & No Sub \\
   %\noalign{\smallskip}
            \hline
     $\sigma_{\rm c}$ (km s$^{-1}$) & $588.5\pm199.5$ & $544.8\pm199.2$ & $567.4\pm250.7$ & $512.5\pm150.3$ \\
     $f_{\rm b}$ & $0.37\pm0.06$ & $0.42\pm0.12$ & $0.36\pm0.10$ & $0.36\pm0.08$ \\
     $\Delta m_{12}$ (mag) & $-0.45\pm0.5$ & $-0.38\pm0.4$ & $-0.39\pm0.47$ & $-0.36\pm0.34$ \\
     \hline
         \end{tabular}
   \end{table}