\begin{table}%t2
\caption{\label{tab:fitparam}Best fit parameters.}
\small%\centerline
 {
 \begin{tabular}{lccc}
 \hline
 \hline
 Parameter$^a$ & Model A     & Model B     & Model C \\
               & pure gas    & gas \& dust & pure gas \\
	       & curv. corr. &  curv. corr &  no curv. corr \\    
 \hline
%&&& \\[-8pt]
 $\chi^2$      & 2341 & 2327 & 2366 \\         
 d.o.f.        & 1316 & 1315 & 1316 \\        
 $f(5)^{b}$    & $1.056\pm 0.009$ & $1.055\pm 0.009$ & $1.035\pm 0.009$ \\
 $f(40)^{b}$   & $0.746\pm 0.016$ & $0.762\pm 0.016$ & $0.854\pm 0.019$ \\
 \hline
\multicolumn{4}{l}{column densities$^{c}$:}\\  	 	 
 \hline
%&&& \\[-8pt]
\ion{H}{i}$^{d,e}$ & $31~750\pm 220$ & $ 9700 \pm 1700 $ & $31~280\pm 220$ \\
\ion{H}{i}$^{d,f}$ &        $-$     & $22~300 \pm 1800 $ & $-$  \\
\ion{H}{i}$^{d,g}$ & $31~750\pm 220$ & $32~060\pm 220   $ & $31~280\pm 220$ \\
\ion{H}{ii}$^h$ &$1752\pm 4$& $1752\pm 4$ & $1752\pm 4$\\
\ion{N}{i}     & $ 2.67\pm 0.24$ & $ 2.72\pm 0.24$ & $ 2.48\pm 0.25$ \\
\ion{O}{i}     & $19.28\pm 0.18$ & $19.83\pm 0.22$ & $19.23\pm 0.18$ \\
\ion{O}{ii}    & $ 0.23\pm 0.14$ & $ 0.25\pm 0.15$ & $ 0.20\pm 0.14$ \\
\ion{Ne}{i}    & $ 4.69\pm 0.21$ & $ 4.66\pm 0.21$ & $ 4.74\pm 0.21$ \\
\ion{Ne}{ii}   & $ 0.46\pm 0.25$ & $ 0.52\pm 0.24$ & $ 0.64\pm 0.25$ \\
\ion{Mg}{i}    & $ 1.14\pm 0.28$ & $ 1.20\pm 0.28$ & $ 1.13\pm 0.28$ \\
\ion{Mg}{ii}   & $ 0.00\pm 0.09$ & $ 0.00\pm 0.10$ & $ 0.00\pm 0.09$ \\
\ion{Fe}{i}    & $ 0.65\pm 0.05$ & $ 0.77\pm 0.04$ & $ 0.65\pm 0.05$ \\
\ion{Fe}{ii}   & $ 0.23\pm 0.06$ & $ 0.14\pm 0.04$ & $ 0.26\pm 0.07$ \\
\hline
\end{tabular}}
\medskip
$^a$ Error bars are all $1\sigma$ for one interesting parameter.\\
$^b$ $f(5)$ and $f(40)$ are the values of the effective area scale factor $f(\lambda)$, Eq.~(\ref{eqn:aeff_cor}), at~5 and 40~\AA.\\ 
$^c$ Ionic column densities are given in units of $10^{21}$~m$^{-2}$. The column
densities of all metals include all phases (dust and gas).\\ 
$^d$ \ion{H}{i} includes in the cross section contributions from neutral~He, C, Si, S, Ar, Ca and Ni assuming proto-solar abundances for these elements.\\
$^e$ For the pure gaseous phase only.\\
$^f$ For the gas \& dust mixture with proto-solar abundances added to the pure gaseous phase above.\\
$^g$ Total column: sum of contributions listed as $b$ and $c$.\\
$^h$ For \ion{H}{ii} the column is derived from the pulsar dispersion measure
assuming that all free electrons originate from hydrogen (see text).
\end{table}