\begin{table}%T4
      \caption{\label{tab:line-ratios}Line intensity ratios between the peak antenna temperatures, assuming a source size of 1.5$''$.}
         \small
	%\centerline
{
         \begin{tabular}{lcc}
            \hline\hline
            \noalign{\smallskip}
            Molecule & Transitions & Ratio$^{{a}}$ \\
              \hline
            \noalign{\smallskip}
	    CN  & $\frac{2_{5/2}-1_{3/2}}{1_{3/2}-0_{1/2}}$ & 0.61~$\pm$~0.39 \\
            \noalign{\smallskip}
	    CN  & $\frac{3_{5/2}-2_{5/2}}{2_{5/2}-1_{3/2}}$ & 0.13~$\pm$~0.04 \\
            \noalign{\smallskip}	    	    
	    HCN & $\frac{3-2}{1-0}$ & 1.01~$\pm$~0.53 \\
            \noalign{\smallskip}	    
	    HCN & $\frac{4-3}{3-2}$ & 0.49~$\pm$~0.14 \\
            \noalign{\smallskip}	    
	    HNC & $\frac{3-2}{1-0}$ & 0.38~$\pm$~0.18 \\
	    \noalign{\smallskip}
	    HNC & $\frac{4-3}{3-2}$ & 0.30~$\pm$~0.10 \\
	    \noalign{\smallskip}
	    HCO$^+$ & $\frac{3-2}{1-0}$ & ~~~0.12~$\pm$~0.04$^{{b}}$ \\
            \noalign{\smallskip}	    	    
	    HCO$^+$ & $\frac{4-3}{3-2}$ & 1.37~$\pm$~0.46 \\
            \noalign{\smallskip}	    	    
            \hline
         \end{tabular}}
         \smallskip
${^a}$ See P\'erez-Beaupuits \etal~(\cite{erez2007}) for the $J=1{-}0$ and $J=3{-}2$ transitions. The low-$J$~lines of \hcop\ were obtained from~Krips \etal~(\cite{Krips2008}).\\
 ${^b}$ This ratio slightly differs from that found by~Krips \etal\ (\cite{Krips2008}) because we use the ratio between the peak main beam temperatures and we corrected the \hcop~$J=1{-}0$~line for the starburst contribution \mbox{factor}. 
\end{table}