\begin{table}%t8
%\centering
\par
\caption{\label{table:KS}Kennicutt-Schmidt law in three radial intervals in M~31.}
\begin{tabular}{ l l l l l l l }
\hline\hline
\noalign{\smallskip}
~~~$R$(kpc) & ~~\ X &~~~~~~ $a_{\rm c}$ &  ~~~~~~ $b$ &   $n$  & ~~~~~~ $r_{\rm c}$& $t$\\
\hline
7--9 & $\Sigma_{\rm GAS}$  &  --0.90~$\pm$~0.04 &1.03~$\pm$~0.06 &  216 &  0.54~$\pm$~0.06 & 9 \\
9--11 &                  &  --1.43~$\pm$~0.06  & 1.67~$\pm$~0.08 &  356  & 0.63~$\pm$~0.04 & 15 \\
11--13  &                &  --1.46~$\pm$~0.06  &  1.55~$\pm$~0.08 & 297 & 0.62~$\pm$~0.05& 13 \\
&&&& & &\\
7--9  &  $n_{\rm GAS}$  &  0.18~$\pm$~0.04  &  0.88~$\pm$~0.06   & 218  &  0.51~$\pm$~0.06  &  9\\
9--11  &         &  0.45~$\pm$~0.04  &  1.50~$\pm$~0.07   & 356  &  0.62~$\pm$~0.04  & 15\\
11--13  &         &  0.35~$\pm$~0.04  &  1.35~$\pm$~0.07   & 297  &  0.62~$\pm$~0.05  & 14\\
\hline
\end{tabular}
\tablefoot {Ordinary least-squares fits of the bisector log~($\Sigma_{\rm SFR}$)~=~$a_{\rm c}~+~b$~log~($X$),
where $\Sigma_{\rm SFR}$ is the face-on surface density of the star formation rate
in $M_{\odot}$~Gyr$^{-1}$~pc$^{-2}$, 
$X$~=~$\Sigma_{\rm GAS}$ is the face-on gas surface density in $M_{\odot}$~pc$^{-2}$ and $X$~=~$n_{\rm GAS}$ is the gas volume density in at cm$^{-3}$. 
$n$ is the number of independent points; $r_{\rm c}$ is the correlation coefficient
and t the student-t test. }
\end{table}