\begin{table}%t1
%\centering
\par
\caption{\label{line_param}Summary of the parameters of the spectral line observations.}
\begin{tabular}{c c c c c c }
\hline\hline \noalign{\smallskip}
Line & $\nu$ & $\Theta_{\rm beam}$ & $T_{\rm sys}$ & $\Delta~v$ & $\eta_{\rm mb}$\\
& (GHz) & (arcsec) & (K) & (km~s$^{-1}$) &\\
(1)&(2)&(3)&(4)&(5)&(6)\\
\hline
\multicolumn{6}{c}{{FCRAO~14~m}}\\
 $^{13}$CO(1--0) & 110.201 & 46 & 294--680 & 0.2 & 0.49\\  
 C$^{18}$O(1--0) & 109.782 & 46 & 291--697 & 0.2 & 0.49 \\
 C$^{17}$O(1--0) & 112.359 & 46 & 290--371 & 0.2 & 0.47\\ 
\hline
\multicolumn{6}{c}{{IRAM~30~m}}\\
$^{13}$CO(2--1) & 220.399 & 11   & 639--1129 & 0.1 & 0.52 \\  
C$^{18}$O(2--1) & 219.569 & 11   & 659--1061 & 0.1 & 0.52\\   
C$^{17}$O(2--1) & 224.714 & 11   & 383--517 & 0.1 & 0.536\\
\hline
\end{tabular}
\tablefoot{Column~(1): the observed line; Col.~(2): the frequency of the transition; Col.~(3): the beam size of the observations; Col.~(4): the typical system temperature, $T_{\rm sys}$, of the observations; Col.~(5): the velocity resolution, $\Delta~v$, of the observations; Col.~(6): the beam efficiency used for every specific frequency.}
\vspace*{2mm}\end{table}