\begin{table}%t8
\caption{\label{table:6}Summary of determination of systemic velocities, velocity dispersions and metallicities for the Hercules dSph galaxy.}
%\centerline
{
\begin{tabular}{l l c c c c c}
\hline\hline
 & Number of stars & $v_{{\rm sys}}$  & $\sigma$  & $\langle {\rm [Fe/H]} \rangle $ & ${\rm [Fe/H]_{Median}}$\\ 
 &  & [${\rm ~ km~ s^{-1}}$] & [${\rm ~ km~ s^{-1}}$] &~dex &~dex \\
\hline
This study & 28 [RGB stars, $c_1$ sel.] & ... & ... &  $-2.35\pm 0.31$ & $-2.25^{\rm +0.14}_{-0.31}$ \\ 
This study &  32 [Only $V_{{\rm rad}}$ sel.] & $40.87\pm 1.42$ & $7.33 \pm 1.08$ & ... & ... \\
This study & 18 [RGB stars with $V_{{\rm rad}}$] & $45.20 \pm 1.09$ & $3.72 \pm 0.91$ & $-2.34\pm 0.30$ & $-2.25^{\rm +0.14}_{-0.20}$ \\
S$\&$G & 29 [Their calculation] & $45.0^a \pm 1.1$ & $5.1^a \pm 0.9 $ & ... & ... \\
S$\&$G+$c_1$ & 13 [$c_1$ sel. sample] & $46.10 \pm 1.30$ & $4.01 \pm 1.08$ & ... & ... \\
Kirby et~al. & 20 [Their sample] & ... & ... & $-2.58^b \pm 0.51$& ... \\
Kirby et~al.+$c_1$ & 12 [$c_1$ sel. sample] & ... & ... & $-2.70 \pm 0.47$ & $-2.72^{\rm +0.35}_{-0.40}$ \\
\hline
\end{tabular}}\medskip
\par
$^a$ Value from \citet{2007ApJ...670..313S}. $^b$ Value from \citet{2008ApJ...685L..43K}.\\
Columns~1 and 2 list the number of stars for each study and a short description of how the stars were selected. Note: S$\&$G indicates the sample of 29 stars from \citet{2007ApJ...670..313S}. Columns~3 and 4 list the systemic velocities and velocity dispersions and their errors. Column~5 lists the mean metallicities. Column~6 lists the median metallicities. Errors for the median metallicity are the upper and lower quartile. For the calculations we use our metallicites based on Str\"omgren photometry, but for the \citet{2008ApJ...685L..43K} sample we use their metallicities. 
\end{table}