\begin{table} %t6
\caption{Beam-averaged results.}\label{tab6}
%\centerline
{\begin{tabular}{lcccccccc}
\hline
\hline
Model & \multicolumn{3}{c}{Beam-averaged column densities} & \multicolumn{2}{c}{Total central mass} & \multicolumn{2}{c}{Face-on mass density}       & Relative mass \\
   & $N$(CO) & $N$(C)    & $N(\hdeux)$ & $M(\hdeux)$  & $M_{\rm gas}$        & $\sigma(\hdeux)$ & $\sigma_{\rm gas}$ & components 1:2 \\
   & \multicolumn{2}{c}{($10^{18}~{\rm cm^{-2}}$)} & ($10^{21}~{\rm cm^{-2}}$) & \multicolumn{2}{c}{($10^{7} \Msun$)} & \multicolumn{2}{c}{($\Msun$/pc$^{-2}$)} & \\
\hline
\multicolumn{9}{c}{IC~342; $N_{\rm H}/N_{\rm C}$ = 2200; $N$(HI)$^{a} = 1.5\times 10^{20}~{\rm cm^{-2}}$} \\
  \hline
1  & 0.8 & 2.3      & 3.3      &  0.5 &  0.6 &  49 &  67 &  0.7 : 0.3 \\
2  & 0.7 & 3.8      & 4.8      &  0.7 &  0.9 &  70 &  96 &  0.4 : 0.6 \\
3  & 0.7 & 1.0      & 4.9      &  0.7 &  1.0 &  72 &  99 &  0.3 : 0.7 \\
\hline
\multicolumn{9}{c}{Maffei~2; $N_{\rm H}/N_{\rm C}$ = 2500; $N$(HI)$^{b} = 1.1 
\times 10^{21}~{\rm cm^{-2}}$} \\
\hline
4  & 1.7 & 1.6      & 3.5      &  0.6 &  0.9 &  28 &  43 &  0.55 : 0.45 \\
5  & 3.6 & 1.3      & 5.5      &  0.9 &  1.4 &  43 &  64 &  0.8 : 0.2 \\
6  & 2.6 & 1.1      & 4.1      &  0.7 &  1.1 &  32 &  49 &  0.7 : 0.3 \\
7  & 2.0 & 1.9      & 4.4      &  0.7 &  1.1 &  32 &  53 &  0.55 : 0.45 \\
\hline
\end{tabular}}
\smallskip
$^a$ Newton (\cite{Newton80}); $^b$ Hurt et~al. (\cite{Hurt96}).
\end{table}