\begin{table}%t1
%\centering
\par
\caption {\label{TabFit}CH$^{+}$ $(0{-}1)$ and $^{13}$CH$^{+}$ $(0{-}1)$ absorption lines analysis. The column
  densities are derived assuming an excitation temperature $T_{\rm ex} = 3$~K.}
\begin{tabular}{l l  c  c  c  c  c  c  c  c}
\hline\hline
\noalign{\smallskip}
Source     & Velocity component & $\upsilon_{\rm min}$ & $\upsilon_{\rm max}$ & 
$N$(CH$^{+}$)                  &
$N$($^{13}$CH$^{+}$)           & 
$50\times N$($^{13}$CH$^{+}$) & 
$N({\rm HCO}^{+})$\tablefootmark{a}      &
$\frac{N({\rm CH}^{+})}{N({\rm HCO}^{+})}$ &
$N_{\rm H}$\tablefootmark{b}           \\
           &                    & km s$^{-1}$        & km s$^{-1}$        & 
$10^{13}$ cm$^{-2}$            & 
$10^{12}$ cm$^{-2}$            & 
$10^{13}$ cm$^{-2}$            & 
$10^{12}$ cm$^{-2}$            &
                               &
$10^{22}$ cm$^{-2}$            \\
\hline
 {\bf \object{W33A}} & 
$\left. \begin{array}{l l l} {\rm star~~forming~~region} \\ {\rm foreground} \end{array} \right. $ & 
$\left. \begin{array}{c c c} 19                              \\ -4               \end{array} \right. $ &
$\left. \begin{array}{c c c} 60                              \\ 19               \end{array} \right. $ &
$\left. \begin{array}{c c c} {>} 16.7                          \\ 0.8 \pm 0.1      \end{array} \right. $ & 
$\left. \begin{array}{c c c}  -                              \\ -                \end{array} \right. $ & 
$\left. \begin{array}{c c c}  -                              \\ -                \end{array} \right. $ & 
$\left. \begin{array}{c c c}  -                              \\ -                \end{array} \right. $ & 
$\left. \begin{array}{c c c}  -                              \\ -                \end{array} \right. $ & 
$0.8 \pm 0.4$ \\[0.4cm]
{\bf \object{W49N}} &
$\left. \begin{array}{l l l} {\rm star~~forming~~region} \\ {\rm foreground} \end{array} \right. $ & 
$\left. \begin{array}{c c c} -20                             \\ 30               \end{array} \right. $ &
$\left. \begin{array}{c c c}  30                             \\ 80               \end{array} \right. $ &
$\left. \begin{array}{c c c} {>} 16.6                          \\ {>}27.7            \end{array} \right. $ & 
$\left. \begin{array}{c c c} {>} 6.7                           \\ 7.8 \pm 0.6      \end{array} \right. $ & 
$\left. \begin{array}{c c c} {>} 33.5                          \\ 39 \pm 3         \end{array} \right. $ & 
$\left. \begin{array}{c c c}  -                              \\ 25 \pm 1         \end{array} \right. $ &
$\left. \begin{array}{c c c}  -                              \\ {>} 11             \end{array} \right. $ & 
$4.1 \pm 0.4$ \\[0.4cm]
{\bf \object{W51}}  & 
$\left. \begin{array}{l l l} {\rm star~~forming~~region} \\ {\rm foreground} \\ {\rm foreground} \end{array} \right. $ & 
$\left. \begin{array}{c c c}  43                             \\ 15               \\ -2               \end{array} \right. $ &
$\left. \begin{array}{c c c}  80                             \\ 43               \\ 15               \end{array} \right. $ &
$\left. \begin{array}{c c c} {>} 12.8                          \\ 1.0 \pm 0.1      \\ 1.7 \pm 0.1      \end{array} \right. $ & 
$\left. \begin{array}{c c c} {>} 5.4                           \\ -                \\ -                \end{array} \right. $ & 
$\left. \begin{array}{c c c} {>} 27.0                          \\ -                \\ -                \end{array} \right. $ & 
$\left. \begin{array}{c c c}   -                             \\ {<} 0.25           \\ 4.1 \pm 0.4            \end{array} \right. $ &
$\left. \begin{array}{c c c}  -                              \\ {>} 40             \\ 4             \end{array} \right. $ & 
$2.5 \pm 0.6$ \\
\hline
\end{tabular}
\tablefoot {
\tablefootmark {a}{From Godard et~al. (2010).}
\tablefootmark {b}{From models of the extinction at 2 $\mu$m by Marshall et~al. (2006).}}
\end{table}