\begin{table}%t8
%\centering
\par
\caption {\label{gas}Emission in CO and \hi{} by the sample
galaxies. Both the fluxes and the errors are in units of $10^{54}$~W~km~(Hz~s)$^{-1}$ for CO, and of
$10^{52}$~W~km~(Hz~s)$^{-1}$ for
\hi. The error column corresponds to the photometric error and does
not take into account the uncertainty in the distance. In some cases,
no error estimate is given for the \hi{} emission because this was not
given in the literature. A hyphen (--) means that no data are
available.}
\begin{tabular}{l c c c c}
\hline\hline
ID & \multicolumn{2}{c}{CO}& \multicolumn{2}{c}{\hi{}}\\
   & Flux & Error & Flux & Error\\
\hline
\multicolumn{5}{c}{$\sigma$-drop sample}\\
NGC~1068 & 114.9 &  6.1  &   71.0 &  4.0 \\
NGC~1097 &  --   &  --   &  256.9 & 10.3 \\
NGC~1808 &  --   &  --   &   80.3 &  4.8 \\
NGC~2460 &  --   &  --   &  235.0 &  9.4 \\
NGC~2639 &  --   &  --   &Very little& --\\
NGC~2775 &  24.3 &  4.4  &   20.4 &  1.8 \\
NGC~3021 &  --   &  --   &   79.2 &  3.2 \\
NGC~3593 &  10.7 &  1.9  &    8.7 &  0.7 \\
NGC~3623 &$<$16.7&  8.4  &   26.5 &  1.4 \\
NGC~3627 &  83.5 &  8.4  &   78.8 &  3.5 \\
NGC~4030 &  55.9 & 11.2  &  202.6 &  8.1 \\
NGC~4303 & 155.0 &  9.6  &  433.7 & 15.6 \\
NGC~4579 &  57.6 & 12.7  &   58.3 &  4.7 \\
NGC~4725 &  40.7 & 14.6  &  139.0 &  6.7 \\
NGC~4826 &  12.4 &  1.5  &   26.6 &  1.3 \\
NGC~6503 &   3.3 &  1.1  &   23.9 &  1.1 \\
NGC~6814 &  16.5 &  3.1  &  162.3 &  6.5 \\
NGC~6951 & 102.6 & 21.4  &  172.5 &  5.5 \\
\hline
\multicolumn{5}{c}{Control sample}\\
NGC~488  &  66.6 & 16.0  &  190.1 &  10.7\\
NGC~864  &  29.0 &  7.4  &  358.9 &  11.5\\
NGC~1566 &   --  &  --   &  312.7 &  17.5\\
NGC~2964 &  17.3 &  3.1  &   86.6 &   3.1\\
NGC~2985 &  39.0 & 13.2  &  361.6 &  28.9\\
NGC~3031 &   --  &  --   &  133.8 &   8.6\\
NGC~3169 &  48.7 &  9.8  &  127.6 &  13.3\\
NGC~3198 &   --  &  --   &  123.8 &   5.9\\
NGC~3227 &   --  &  --   &   81.6 &   4.9\\
NGC~3368 &   --  &  --   &   73.8 &   3.8\\
NGC~3675 &  32.8 &  6.4  &   89.1 &   3.2\\
NGC~3718 & $<$$8.3$&  4.4  &  381.1 &  15.2\\
NGC~4102 &  27.3 &  6.2  &   38.1 &   2.3\\
NGC~4151 &  13.6 &  3.2  &  122.5 &   5.4\\
NGC~4459 & $<$$5.0$&  2.5  &   --   &  --  \\
NGC~5055 & 124.2 &  9.0  &  693.4 &  36.1\\
NGC~6340 &   --  &  --   &   55.3 &   4.4\\
NGC~6501 &   --  &  --   &  103.5 &  17.4\\
NGC~7331 &  75.4 &  9.7  &  366.4 &  10.3\\
NGC~7742 &   --  &  --   &   59.4 &   2.1\\
\hline
\end{tabular}
\end{table}