\begin{table}%t2
\caption{Physical parameters of the \zabs~= 1.8073~metal absorber
  towards \object{HS~0747+4259} derived by the MCI~procedure with the
  Haardt \& Madau and modified UV~background spectra (marked,
  respectively, by~HM96 and~S1 in Fig.~\ref{fig2}).  Column densities are given
  in~\cm.}\label{tbl_2}
%\centerline
{
\begin{tabular}{lccccc}
\hline
\hline
  &\multicolumn{2}{c}{subsystem $A$} 
  &\multicolumn{2}{c}{subsystem $B$} 
  &\multicolumn{1}{c}{subsystem $C^d$}\\
  &\multicolumn{2}{c}{$-90$ \kms\ $< v < 0$ \kms} 
  &\multicolumn{2}{c}{0 \kms\ $< v < 80$ \kms} 
  &\multicolumn{1}{c}{$-20$ \kms\ $< v < 20$ \kms}\\
Parameter$^a$ & HM96 & S1 & HM96 & S1 &    \\
 (1) & (2) & (3) & (4) & (5) & (6)  \\
\hline
$U_0$&8.1E--3&4.5E--3&6.2E--3&4.1E--3& \\
$N_{\rm H}$  & 1.2E18 & 7.7E17 & 7.6E18 & 4.7E18 &  \\
$\sigma_{v}$, \kms & 15.0 & 13.0 & 19.8 & 23.5 &  \\
$\sigma_{y}$& 0.55 & 0.60 & 0.68 & 0.64 &  \\
$Z_{\rm C}$&8.3E--5 & 1.0E--4 & 1.2E--5 & 1.7E--5 &  \\
$Z_{\rm O}$&2.5E--4 & 3.6E--4 & 4.2E--5 & 6.0E--5 &  \\
$Z_{\rm Si}$&1.1E--5 & 1.6E--5 & 1.8E--6 & 2.9E--6 &  \\
$[Z_{\rm C}]$&$-0.47$ &$-0.37$ & $-1.30$ & $-1.15$ & \\
$[Z_{\rm O}]$&$-0.27$ & $-0.10$ & $-1.04$ &$-0.90$ & \\
$[Z_{\rm Si}]$&$-0.46$ & $-0.31$ & $-1.25$ & $-1.04$ &  \\
$N$(H~{\sc i})&1.4E15 & $(1.4\pm0.4)$E15 & 1.0E16 
& $(1.2\pm0.3)$E16 & $<$3.0E14 \\
$N$(C~{\sc ii})&3.6E12$^b$ &4.3E12$^b$ & 4.8E12 
& $(7.0\pm2.0)$E12 & $\ldots$ \\
$N$(O~{\sc ii})&8.1E12$^b$ &1.0E13$^b$ &1.2E13$^b$ 
&2.2E13$^b$ & $\ldots$ \\ 
$N$(Si~{\sc ii})&4.9E11$^b$ &5.6E11$^b$ & 6.9E11 
& $(9.0\pm3.0)$E11 & $\ldots$ \\
$N$(C~{\sc iii})&7.0E13 & 5.5E13$^c$ & 7.3E13 & 6.0E13$^c$ 
& $(1.0\pm0.3)$E13$^e$  \\
$N$(O~{\sc iii})&2.2E14 &2.0E14$^c$ & 2.5E14 & 2.1E14$^c$ & $\ldots$  \\
$N$(Si~{\sc iii})&5.8E12 & $(6.1\pm0.9)$E12& 8.4E12 & 
$(8.1\pm1.2)$E12 & $\ldots$ \\
$N$(C~{\sc iv}) &1.7E13&$(1.50\pm0.15)$E13&1.1E13 & 
$(1.1\pm0.1)$E13 & $(1.9\pm0.2)$E13 \\
$N$(O~{\sc iv}) &5.6E13 &$(6.2\pm2.0)$E13 &4.9E13$^b$ 
& 5.0E13$^b$ & $(2.9\pm0.9)$E14$^e$ \\
$N$(Si~{\sc iv}) &3.4E12 &$(2.6\pm0.4)$E12 & 2.2E12 & 
$(2.0\pm0.4)$E12 & $\ldots$ \\
$N$(N~{\sc v})&$\ldots$ &$\ldots$ & $\ldots$ & $\ldots$ &
 $\leq$2.0E12  \\
$N$(O~{\sc vi}) &$\ldots$ &$\ldots$ &$\ldots$ & $\ldots$ 
 & $(1.10\pm0.25)$E14  \\
$\langle T \rangle$, K & 1.3E4 & 1.5E4 & 2.0E4 & 2.0E4 & \\
$n_{\rm H}$, \cmm & 3.3E--3 & 6.6E--3 & 5.0E--3 & 7.6E--3 & \\ 
$L$, kpc & 0.13 & 0.04 & 0.5 & 0.2 & \\ 
\hline
\end{tabular}}
\medskip
$^aZ_{\rm X} = N_{\rm X}/N_{\rm H}$; $[Z_{\rm X}] = \log~ (N_{\rm X}/N_{\rm H}) - \log~ (N_{\rm X}/N_{\rm H})_\odot$; $^b$~calculated using the velocity and density distributions estimated from the metal profiles marked by the horizontal bold lines in Fig.~\ref{fig1}; $^c$~uncertainty cannot be estimated since line is corrupted by background subtraction; $^d$~column densities for    putative \ion{O}{vi}~absorption at $-70$~\kms~$< v < -20$~\kms\ and at $30$~\kms~$< v < 50$~\kms\ are not given because of probable blending with some Ly$\alpha$~forest lines (observed intensities of \ion{O}{vi}$\lambda1032$ and~$\lambda1037$ are inconsistent); $^e$~can be blended.
\end{table}