\begin{table}%t4
%\centering
\par
\caption{\label{ta:3d}Peculiar motions.}
$$
\small \begin{tabular}{lr@{$\pm$}lr@{$\pm$}lr@{$\pm$}lr@{$\pm$}lr@{$\pm$}lr@{$\pm$}l}
\hline\hline \noalign {\smallskip}
Source & \multicolumn{6}{c}{$R_0=8.5$~kpc, $\Theta_0=220~{\rm km~s^{-1}}$} & \multicolumn{6}{c}{$R_0=8.4$~kpc, $\Theta_0=254~{\rm km~s^{-1}}$}\\
& \multicolumn{2}{c}{$U$} & \multicolumn{2}{c}{$V$} & \multicolumn{2}{c}{$W$} & \multicolumn{2}{c}{$U$} & \multicolumn{2}{c}{$V$} & \multicolumn{2}{c}{$W$}\\
& \multicolumn{2}{l}{(${\rm km~s^{-1}}$)}& \multicolumn{2}{l}{(${\rm km~s^{-1}}$)}&\multicolumn{2}{l}{(${\rm km~s^{-1}}$)} & \multicolumn{2}{c}{(${\rm km~s^{-1}}$)}& \multicolumn{2}{c}{(${\rm km~s^{-1}}$)}&\multicolumn{2}{c}{(${\rm km~s^{-1}}$)}\\
\hline
%ON~1    & $13\pm7$ & $-19\pm3$ & $7\pm9$ & &$4\pm7$ & $-20\pm3$& $7\pm9$ \\
ON~1    & $18$&$8$ & $-19$&3 & $4$& $10$ &$7$&$8$ & $-21$&$3$& $4$&$10$ \\
L~1206   & $2$&$4$ & $-16$&$2$ & $0$&$6$  &$-1$&$4$ & $-16$&$2$& $0$&$6$\\
L~1287   & $13$&$2$ & $-18$&$2$ & $-3$&$2$  &$10$&$2$ & $-18$&$2$ &$-3$&$3$\\
NGC~281-W& $13$&$2$ & $-3$&$2$ & $-9$&$2$  &$6$&$2$& $-3$&$2$ &$-9$&$2$\\ 
S~255    & $1$&$3$ & $-4$&$12$ & $3$&$7$  & $2$&$3$ & $-4$&$12$ & $3$&$7$\\
\hline
\end{tabular}
$$
\end{table}