\documentstyle[12pt,aj_pt4]{article}
%
\def\sgr{the Sagittarius dwarf spheroidal}

\begin{document}

\begin{deluxetable}{crrrrrr}
\footnotesize
\tablecaption{The globular clusters of \sgr}
\tablewidth{0pt}
\tablehead{
\colhead{Cluster} & \colhead{ra (1950)}   & \colhead{dec (1950)}   & \colhead{[Fe/H]} & 
\colhead{$v_{Gal}$ (km/s)}  & \colhead{$T$ (Gyr)} & \colhead{$M_V$}
}
\startdata
M54   &  18 51 51.2 & $-$30 32 34 & $-1.55 \pm 0.10$ & $172 \pm 1 $ &        & $-10.0$ \nl
Ter~7 &  19 14 26.2 & $-$34 44 54 & $-0.4 \rightarrow -1$     & $186 \pm 4 $ & 9--12  & $-6.0$ \nl  
Ter~8 &  19 38 30.3 & $-$34 07 05 & $-1.99 \pm 0.08$ & $158 \pm 8 $ & 16--19 & $-5.0$ \nl  
Arp~2 &  19 25 33.9 & $-$30 27 26 & $-1.70 \pm 0.11$ & $154 \pm 10$ & 13--14 & $-5.3$ \nl  
\enddata
\end{deluxetable}

\end{document}