\begin{table}%t3
%\centering
\par
\caption{\label{tab4}Age and metallicity components.}
\par
\begin{tabular}{rccc}
\hline\hline
      &$Z = 0.05$ & $Z = 0.02$ & $Z = 0.008$ \\
\hline
13~Gyr & A1  & A2  & A3  \\
 5~Gyr & B1  & B2  & B3  \\
 1~Gyr &     & C2  &     \\
\hline
\end{tabular}
\end{table}