\begin{table}%T2
\caption{\label{table2}Spiral models: parameters.}          
\small                                  
%\centering
\par
\begin{tabular}{c c c c c}                         
\hline\hline                                     
$\Sigma_{0}$          & $R_{\rm D}$   & $\nu$          &$\tau_{\rm inf}(R)$ & IMF     \\  
($M_{\odot}/{\rm pc}^{2}$ ) & (kpc)    &  (Gyr$^{-1}$)    &    (Gyr)       &           \\
\hline                                 
  200 & 2   & 0.3 &      $R \cdot 1.03{-}1.27$                          &Scalo \\   
  491 & 3.5 & 1   &      $R \cdot 1.03{-}1.27$                          & Scalo \\ 
  2000 & 5 & 2    &      $R \cdot 0.75{-}0.5$                              & Scalo \\  
\hline                                         
\end{tabular}
\end{table}