\begin{table}%t2
\caption{\label{bid2}Column densities for methanol isotopomers towards IRAS4A, derived by fixing the rotational temperature to the one derived for CH$_2$DOH, and ratios  between isotopomers.}
\small%\centering
\par
\begin{tabular}{c|ccc|cccc}
\hline
\hline
Source  &  $T_{\rm rot}$ & CH$_2$DOH  &  $\chi^2_{\rm red}$ & CH$_3$OD & CHD$_2$OH  & \underline{CH$_3$OD} & \underline{CHD$_2$OH} \\
size  & (K) &    ($\times$10$^{14}$~cm$^{-2}$) & &   ($\times$10$^{13}$~cm$^{-2}$) &   ($\times$10$^{13}$~cm$^{-2}$)  & CH$_2$DOH & CH$_2$DOH  \\
\hline
10$''$  & 27.1~$\pm$~1.3 & 4.3~$\pm$~0.4 & 13.5 & 3.1~$\pm$~0.7 & 11~$\pm$~1.7 & (7.2~$\pm$~1.8)$\times$10$^{-2}$ & 0.26~$\pm$~0.05 \\
15$''$  & 31.3~$\pm$~1.7 & 2.4~$\pm$~0.3 & 8.5 & 1.6~$\pm$~0.4 & 6.3~$\pm$~1.0  & (6.7~$\pm$~1.9)$\times$10$^{-2}$ & 0.26~$\pm$~0.05 \\
20$''$  & 36.2~$\pm$~2.3 & 1.8~$\pm$~0.2 & 5.2 & 1.2~$\pm$~0.3 & 5.0~$\pm$~0.9  & (6.7~$\pm$~1.8)$\times$10$^{-2}$ & 0.28~$\pm$~0.06 \\
25$''$  & 42.2~$\pm$~3.2 & 1.7~$\pm$~0.2 & 3.2 & 1.4~$\pm$~0.3 & 4.4~$\pm$~0.8  & (8.2~$\pm$~2.0)$\times$10$^{-2}$ & 0.26~$\pm$~0.06 \\
30$''$  & 46.2~$\pm$~3.8 & 1.7~$\pm$~0.2 & 2.9 & 1.5~$\pm$~0.4 & 3.9~$\pm$~0.7  & (8.8~$\pm$~2.6)$\times$10$^{-2}$ & 0.23~$\pm$~0.05 \\
\hline
\end{tabular}
\end{table}