\begin{table}%t2
\caption{\label{tab:oxygen}Components of oxygen line decomposition.}
%\centering
\small
\begin{tabular}{ l c c c c c  }
\hline\hline
Component & $v$ & $u$ &  $A_1$ & $A_2$ & $n$ \\
         & \multicolumn{2}{c}{(km~s$^{-1}$)} &  &  & cm$^{-3}$ \\
\hline
&&&&& \\[-8pt]
  symmetric & 0     & 1800 &  0.59   & 0.27    & $1.25\times10^9$ \\
  red       & 1080  &  900 &  0.14   & 0.049   & $2.0\times10^8$ \\
  blue      & --450  &  480 &  0.32   & 0.20    & $2.8\times10^9$ \\
\hline
\end{tabular}
\end{table}