\begin{table}%t1
\caption{List of the observed DLA and sub-DLA~systems with column densities and metallicities taken from the literature.}\label{tab:list_obj}
\small%\centerline
{
\begin{tabular}{llllllll}
\hline
\hline
 Coordinate name & Alt. name   & $z_{{\rm em}}$ &
 $z_{{\rm abs}}$ & $\log$\nhi &   [Fe/H] & [Si/H]  & Ref.\\
\hline
Q0151+048A &\object{PHL~1222}   & 1.93 & 1.934 & 20.36 $\pm$ 0.10 & & & (1)\\
Q0953+4749 & \object{PC 0953+4749} & 4.457& 3.404 & 21.15 $\pm$ 0.15 &
   $>$--2.178 & $>$--2.09   & (2, 3)\\
                                   &  &   & 3.891 & 21.20 $\pm$ 0.10 &
  $>$--1.712  & $>$--1.60 \\
  &                    &                  & 4.244 & 20.90 $\pm$ 0.15 &
   --2.50 $\pm$ 0.17 &--2.23 $\pm$ 0.15 \\
\object{Q1347+112} &  & 2.679&  2.471 & 20.3     & &  &  (4, 5, 6)\\
   &                &      &  2.05  & 20.3$^\dagger$ & &  &  (7)\\
Q1425+606& \object{SBS 1425+606}  &  3.163 & 2.827 & 20.30 $\pm$ 0.04
   & --1.33 $\pm$ 0.04 & $>$--1.03 & (8, 9, 10, 21) \\
\object{Q1451+1223}& B1451+123 & 3.246 &  2.469 & 20.39 $\pm$ 0.10 &
   --2.54 $\pm$ 0.12 & --1.95 $\pm$ 0.16  & (11, 24)\\
  &  &  &  3.171 & 19.70 $\pm$ 0.15 & --1.87 $\pm$ 0.16 & --1.62 $\pm$ 0.15 & (19) \\
   & &  &  2.254 & 20.30 $\pm$ 0.15 & --1.47 $\pm$ 0.17 & $>$--0.40 &  (6, 12, 19)\\
\object{Q1759+7539} & \object{GB2 1759+756}  &  3.05 &    2.625 & 20.76 $\pm$ 0.10
   & --1.21 $\pm$ 0.10 &--0.82 $\pm$ 0.10 & (13, 18, 20)\\
  &          &    & 2.91 &  19.8 & --1.65 $\pm$ 0.01 & --1.26 $\pm$ 0.01 & (18)\\
Q1802+5616 & \object{PSS J1802+5616} & 4.158 & 3.391 & 20.30 $\pm$ 0.10 &
 --1.54 $\pm$ 0.11& $>$--1.55 & (23)\\ 
  &  &  &   3.554 & 20.50 $\pm$ 0.10 &  --1.93 $\pm$ 0.12& $>$--1.82\\
  &  &  &   3.762 & 20.55 $\pm$ 0.15 &  --1.82 $\pm$ 0.26& $>$--1.74\\
  &  &  &   3.811 & 20.35 $\pm$ 0.20 &  --2.19 $\pm$ 0.23& --2.04 $\pm$ 0.22\\
Q2155+1358 & \object{PSS J2155+1358} & 4.256 & 3.316 & 20.55 $\pm$ 0.15
& $>$--1.68 & --1.26 $\pm$ 0.17 & (3)\\
  &  &  &   3.142 & 19.94 $\pm$ 0.10 & --2.21 $\pm$ 0.21 & --1.85 $\pm$ 0.12 & (14, 19) \\
 &   &  &   3.565 & 19.37 $\pm$ 0.15 & $<$--2.40 & --1.27 $\pm$ 0.16 & (14, 19)\\
 &   &  &   4.212 & 19.61 $\pm$ 0.15 & --2.18 $\pm$ 0.25 & --1.92 $\pm$ 0.11 & (14, 19)\\
\object{Q2233+131}&  & 3.295 & 3.153 & 20.0   & $>$--1.4 $\pm$ 0.1 & $>$--1.04 &(15, 16, 17) \\
 &   &  & 2.551 & 20.0   & &  & (12,16)\\
\hline
\end{tabular}}
\medskip
$^\dagger$ Denotes a system where the reported \nhi\ needs to be confirmed
through high resolution spectroscopy. References for either DLA~redshifts or metallicities: (1)~\citet{moller98}; (2)~\citet{schneider91}; (3)~\citet{prochaska03b}; (4)~\citet{smith86};
(5)~\citet{wolfe86}; (6)~\citet{turnshek89}; (7)~\citet{wolfe95}; (8)~\citet{chaffee94}; (9)~\citet{stephanian96}; (10)~\citet{prochaska02}; (11)~\citet{bechtold94}; (12)~\citet{lanzetta91}; (13)~\citet{prochaska01}; (14)~\citet{peroux03}; (15)~\citet{steidel95}; (16)~\citet{lu97}; (17)~\citet{lu98}; (18)~\citet{outram99}; (19)~\citet{dessauges03}; (20)~\citet{prochaska02b}; (21)~\citet{lu96}; (22)~\citet{prochaska03}; (23)~\citet{prochaska03c}; (24)~\citet{petitjean00}.
\end{table}