\begin{table}%t1
\caption{Mean metallicity profile.}  \label{tab: values}
%\centerline
 {\small    \begin{tabular}{ll}
    \hline \hline\noalign{\smallskip}
    Ring$^a$ & Metallicity$^b$ \\
    \hline
    0.00--0.04 & $0.450\pm0.010$ \\
    0.04--0.08 & $0.352\pm0.009$ \\
    0.08--0.12 & $0.294\pm0.010$ \\
    0.12--0.18 & $0.262\pm0.010$ \\
    0.18--0.24 & $0.230\pm0.013$ \\
    0.24--0.32 & $0.245\pm0.017$ \\
    0.32--0.45 & $0.218\pm0.023$ \\
    \hline
  \end{tabular}}
\smallskip
 Notes:  $^a$ in units of $R_{180}$; $^b$ in solar units \citep{anders89}.
\end{table}