\begin{table}%t3
\caption{\label{tab:corre}Pearson coefficients ($r$) and slopes~($n$) derived from the ``relative errors'' method for correlations between the two quantities shown in the first column.} 
%\centering
\small
\begin{tabular}{l c c c}
\hline \hline\noalign{\smallskip}
&  $r$ & $n$ & $n_1$\\
\hline
$\log \Sigma_{\rm SFR} - \log \Sigma_{\rm H_2}$          & 0.42 & $2.22\pm 0.07$  &1.46 $\pm$ 0.34\\
$\log \Sigma_{\rm SFR} - \log \Sigma_{\rm H_I}$          & 0.24 & $1.62\pm 0.03$  &1.11 $\pm$ 0.15\\
$\log \Sigma_{\rm SFR} - \log \Sigma_{\rm H_{tot}}$        & 0.43  & $2.59\pm 0.05$ &1.67 $\pm$ 0.25\\
$\log \Sigma_{\rm SFR} - \log \left(\Sigma_{\rm H_2}/\rho^{-0.5}_{\rm ISM}\right)$  & 0.62 & $1.16\pm 0.04$ &1.00 $\pm$ 0.01\\
$\log \Sigma_{\rm SFR} - \log \rho_{\rm ISM}$ & 0.71 & $1.07\pm 0.02$ &0.97 $\pm$ 0.01 \\
$\log \Sigma_{\rm SFR} - \log \tau_{160}$ & 0.81 & $1.13\pm 0.02$ &1.01 $\pm$ 0.02 \\[2pt]
\hline
\end{tabular}
\tablefoot{The SFR per unit area, $\Sigma_{\rm SFR}$, is~traced by the FUV~emission corrected for extinction. Only positions where the CO~luminosity is above the 2$\sigma$~limit have been considered at a spatial resolution of 180~pc. The surface density of molecular, atomic and total gas are $\Sigma_{\rm H_2}$, $\Sigma_{\rm H_I}$
and $\Sigma_{\rm H_{tot}}$ respectively. $\rho$~is the volume density of the ISM  and 
$\tau_{160}$ the dust opacity. $n_1$~is the OLS~slope as described in the~text.}
\end{table}