\begin{table}%t4
%\centering
\par
\caption{\label{tab_em_ratio_med}Median values of the ratio between the dust emissivity in the
molecular phase and in the atomic phase for each studied case.  Error
bars represent the $\pm$1-$\sigma$ dispersion around each
value.}
\begin{tabular}{  c   c   c   c }
\hline
\hline
$\rm \lambda$ ($\mic$)& $\rm \epsilon_{CO}/\epsilon_{HI}$ & $\rm \epsilon_{CO}/\epsilon_{HI}$  &  $\rm \epsilon_{CO}/\epsilon_{HI}$\\
 & Case 1: \CaseOne & Case 2: \CaseTwo & Case 3: \CaseThree \\
\hline
 100 & 0.8 $\pm$ 0.7  & 3.1 $\pm$ 2.9   & 0.2 $\pm$ 0.2 \\
 140 & 0.7 $\pm$ 0.5  & 2.1 $\pm$ 1.6 & 0.2 $\pm$ 0.2 \\
 240 & 0.8 $\pm$ 0.4  & 1.5 $\pm$ 0.8 & 0.4 $\pm$ 0.2  \\
 550 & 0.8 $\pm$ 0.3  & 0.7 $\pm$ 0.2  & 0.6 $\pm$ 0.2 \\
 850 & 0.6 $\pm$ 0.2  & 0.5 $\pm$ 0.2  & 0.5 $\pm$ 0.2 \\
 1400 & 0.8 $\pm$ 0.2 & 0.8 $\pm$ 0.2  & 0.5 $\pm$ 0.1  \\
 2100 & 0.7 $\pm$ 0.2 & 0.6 $\pm$ 0.3  & 0.3 $\pm$ 0.2  \\
 3200 & 0.7 $\pm$ 0.2 & 0.7 $\pm$ 0.4 & 0.3 $\pm$ 0.3 \\
\hline
\end{tabular}
\end{table}