\begin{table}%t3
\caption{\label{tab:obs3}Main contributors to the heating rates (erg~s$^{-1}$~cm$^{-3}$) in several models (See Table~\ref{tab:obs}).}
%\centering
\par
 \begin{tabular}{cccc}
  \hline \hline \noalign{\smallskip}
   $A_{\rm v}=3$ mag & & &\\
   heating sources & Model 1 & Model 8 & Model 18\\
   FUV & $8.8 \times 10^{-24}$& $8.8 \times 10^{-23}$& $1.7 \times 10^{-23}$\\
   $H$ & $1.0 \times 10^{-20}$& $1.0 \times 10^{-20}$& $1.0 \times 10^{-20}$\\
   Cosmic rays & $1.0 \times 10^{-21}$ & $3.4 \times 10^{-20}$& $4.0 \times 10^{-23}$\\
   \hline
   $A_{\rm v}=8$ mag & & &\\
   heating sources & Model 14 & Model 8 & Model 18\\
   FUV & $8.8 \times 10^{-26}$& $7.6 \times 10^{-27}$&$1.3 \times 10^{-27}$ \\
   $H$ & $1.0 \times 10^{-22}$& $1.0 \times 10^{-20}$& $1.0 \times 10^{-20}$\\
   Cosmic rays & $2.0 \times 10^{-22}$& $2.9 \times 10^{-20}$& $4.7 \times 10^{-23}$\\
   \hline
\end{tabular}
\vspace*{6.5mm}
\end{table}