\begin{table}%t1
%\centering
\par
\caption{\label{tab1}Model input parameters (definitions see Kneiske et~al. \cite{Kneiske2004}).} 
 \begin{tabular}{lllll} 
 \hline \hline \noalign{\smallskip}
 & $\alpha$ & $\beta $ & $z_p$ & $ \dot{\rho_\ast}(z_p)$  \\ 
 &&&&[$M_\odot$~Mpc$^{-3}$ yr$^{-1}$] \\ 
 \hline 
 \bf{Strict lower-limit model}  &&&& \\ 
 $SFR_ 
 {OPT}$   & 3.5 & --1.2 & 1.2 & 0.07 \\ 
 $SFR_{LIG}$   & 4.5 & --1.0    & 1.2 & 0.06 \\ 
 $f_{esc}=0$ &	   &	  &     &     \\ 
 $c_2 = 10^{-24}$ &&&&\\ 
      \hline 
 \end{tabular} 
  \end{table}