\begin{table}%t1
  \caption{\label{table:simu}Simulation details.}   
  %\centering
\par
  \begin{tabular}{c c}
    \hline\hline\\[-3mm]
    Number of bodies & $256^3$ \\ 
    Particle mass & $8.03\times 10^9$ $M_{\odot}$\\
    Box size & 150 Mpc\\
    Omega matter $\Omega_{\rm M}$ & 0.333\\
    Omega lambda $\Omega_{\Lambda}$ & 0.667\\
    Hubble parameter $h$ & 0.667\\
    $\sigma_8$ & 0.880\\
    Initial redshift & 35.6\\
    \hline
  \end{tabular}
\end{table}