\begin{table}%t7
\caption{Electron density and radial velocity statistics.}
\label{statistics}
%\centering
$$
\begin{tabular}{l@{~~~~~}l@{~~~~~}l@{~~~~~}l@{~~~~~}l@{~~~~~}l}
\hline
\hline
& \multicolumn{2}{c}{$v_{\rm LSR}$ (km s$^{-1}$)} & & \multicolumn{2}{c}{$N_{\rm e}$ (cm$^{-3}$)}\\ 
\cline{2-3}\cline{5-6}
& NGC~2579 & ESO~379-9 & & NGC~2579 & ESO~379-9 \\
\hline
$N$      & 298   & 40    & & 298    & 40  \\
min      & 42.22 & 56.76 & & $<$100 & 133 \\
$Q1$     & 50.00 & 58.46 & & 225    & 225 \\
median   & 53.03 & 61.33 & & 376    & 303 \\
$Q3$     & 57.00 & 63.91 & & 518    & 354 \\
max     & 68.98 & 66.82 & & 1886   & 530 \\
mean     & 54.70 & 61.40 & & 435    & 305 \\
$\sigma$ & 5.28  & 2.68  & & 491    & 76  \\
\hline
\end{tabular}
$$
\end{table}