\begin{table}%t2
\caption{\label{orbite}Orbital parameters.}
\par
\small%%\centerline

 {
  \begin{tabular}{ccccc}
    \hline\hline
%&&&& \\[-8pt]
    Orbit id & $r_{\rm ini}^{{a}}$ &  $v_{\rm ini}^{{b}}$  & $L^{{c}}$  & $E^{{d}}$ \\
         & [kpc] & [100 $\rm km~s^{-1}$] &  [$\rm 10^2~km~s^{-1}~kpc$] &  [$\rm 10^4~km^2~s^{-2}$]\\
       \hline
       01& 100.& 2.0&57.0&0.\\
       05& 100.& 2.0  &80.0&0.\\
       15& 70.0& 1.6&41.3&--1.57\\       
       \hline  
\end{tabular}}
\medskip
$^{{a}}$ Initial distance between the two galaxies;
$^{{b}}$~absolute value of the initial relative velocity;
$^{{c}}$~$L=\mid\vec{r}_{\rm ini} \times \vec{v}_{\rm ini}\mid$;
$^{{d}}$~$E={v_{\rm ini}}^2/2-G(m_1+m_2)/r_{\rm ini}$, with $m_1=m_2=2.3$~$\times$~$10^{11}~M_{\odot}$.
\end{table}