\begin{table}%t1
%%\centering
\par
\caption{Mean velocities and velocity dispersion of the sample stars.}\label{tab1}
%%\begin{center}
$$
\begin{tabular}{l r r @{$~\pm~$}l r @{$~\pm~$}l r @{$~\pm~$}l r @{$~\pm~$}l r @{$~\pm~$}l r @{$~\pm~$}l}
  \hline
  \hline
  % after \\: \hline or \cline{col1-col2} \cline{col3-col4} ...
    & $N$ &
  \multicolumn{2}{c}{$\langle U \rangle$}        & \multicolumn{2}{c}{$\langle V \rangle$}        & \multicolumn{2}{c}{$\langle W \rangle$}      &
  \multicolumn{2}{c}{$\sigma_{U}$} & \multicolumn{2}{c}{$\sigma_{V}$} & \multicolumn{2}{c}{$\sigma_{W}$} \\
  dex&&\multicolumn{2}{c}{}&\multicolumn{2}{c}{}&\multicolumn{2}{c}{km s$^{-1}$}&\multicolumn{2}{c}{}&\multicolumn{2}{c}{}&\multicolumn{2}{c}{}\\
  \hline
  \bf{CLLA-TYC2+HIP}& &\multicolumn{1}{c}{} &\multicolumn{1}{c}{} &\multicolumn{1}{c}{} &
  \multicolumn{1}{c}{} &\multicolumn{1}{c}{} &\multicolumn{1}{c}{}  \\
  ${\rm{[Fe/H]}}>-1.0$ & $381$ & $-11$&$4$ & $-44$&$3$ & $-4$&$2$ & $74$&$2$ & $50$&$1$ & $37$&$1$ \\
  $-1.6 \le $ [Fe/H] $ \le-1.0$ & $49$ & $-35$&$23$ & $-163$&$12$ & $-1$&$11$ & $158$&$11$ & $85$&$6$ & $74$&$5$ \\
  ${\rm{[Fe/H]}}<-1.6$ & $53$ & $-5$&$26$ & $-219$&$13$ & $-1$&$13$ & $189$&$13$ & $97$&$7$ & $98$&$7$\\
  \hline
\bf{CLLA-Tycho~2}& & \multicolumn{1}{c}{}& \multicolumn{1}{c}{}&
\multicolumn{1}{c}{}&
\multicolumn{1}{c}{} &\multicolumn{1}{c}{} &\multicolumn{1}{c}{}  \\
  ${\rm{[Fe/H]}}>-1.0$ & $169$ & $-9$&$8$ & $-91$&$6$ & $-5$&$4$ & $110$&$4$ & $81$&$3$ & $58$&$2$ \\
  $-1.6 \le $ [Fe/H] $ \le -1.0$ & $50$ & $51$&$17$ & $-180$&$10$ & $4$&$9$ & $121$&$9$ & $68$&$5$ & $61$&$4$ \\
  ${\rm{[Fe/H]}}<-1.6$ & $40$ & $36$&$25$ & $-205$&$14$ & $-19$&$12$ & $157$&$12$ & $87$&$7$ & $77$&$6$\\
  \hline
\end{tabular}
$$
\end{table}