\begin{table}%t3
      \caption{Mean characteristics of MGs as function of the lower
        limit of lifetime; each mean value is given together with
		its $\pm$$ 1 \sigma$ scatter around the mean.
        \label{tab3}}
\par
     $$
         \begin{array}{p{0.15\linewidth}cccccc}
            \hline\hline
            \noalign{\smallskip}
             \rm{Limit} & \rm{Lifetime} & \rm{Drift }&\rm{Travel} & 
             \rm{Area} & \rm{Number} \\
                        &               &\rm{velocity} &
                        \rm{distance}&& \\
                        & \rm{[min]}    & \rm{[m~s^{-1}]}   & \rm{[Mm]}
                        &\rm{[Mm^{2}]}& \\
            \noalign{\smallskip}
            \hline
            \noalign{\smallskip}
            $\geq$1\ h & 158 & 304 & 2.5 & 9.9 & 2022  \\
                        &\pm107&\pm180&\pm1.8& \pm4.0     &       \\
             $\geq$2\ h & 222 & 262 & 3.2 & 10.7 & 1106\\
                         &\pm109 &\pm150 &\pm1.9 &\pm3.7  &     \\
            $\geq$4\ h & 343 & 207 & 4.1 & 11.9 & 366 \\
                        & \pm108&\pm111&\pm2.3&\pm3.6& \\
            $\geq$6\ h & 472 & 176 & 4.9 & 12.9 & 113 \\
                        & \pm106 & \pm99&\pm2.8&\pm3.6& \\
            $\geq$8\ h & 573 & 163 & 5.5 & 13.7 & 44\\
                        & \pm100&\pm90&\pm3.0&\pm3.8& \\
            \noalign{\smallskip}
            \hline
         \end{array}
     $$
   \end{table}