\begin{table}%t2 
\caption{Total column densities derived using the LTE assumption (see the
text). For the three cores in the  "head'' appropriate velocity components were
used (see  Table~\ref{cores}). The formal errors are 10--15\%, which include
intensity calibration ($\sim$10\%) and spectral noise.} 
\par
\label{ltecoldens} 
%\centering
\par
$$
        \hskip0.3cm \begin{array}{lccccccccccrccrccr} 
\hline\hline  
\noalign{\smallskip} 
\par
 {\rm Molecule}  &&  [{\rm cm}^{-2}] & & & {\rm H1a} & & &
      {\rm H2a} & & & {\rm H2b} & &  &{\rm N1a} & & &  
      {\rm T1a}\\  
\noalign{\smallskip} 
\hline 
\noalign{\smallskip} 
\par
{\rm ^{13}CO}  &&   [10^{15}]    &&& 6.1  &&& 5.9 &&& 
7.5  &&&  13.9 &&&  7.9 \\ 
{\rm C^{18}O}     &&  [10^{15}]    &&& 1.2 &&&  1.9  &&& 1.6  
&&&  2.7  &&& 1.1\\ 
{\rm C^{34}S}  &&  [10^{11}]     &&& 4.3 &&& 7.7   &&& 11.5  &&& 
14.0  &&& 11.2 \\ 
{\rm H^{13}CN} &&   [10^{11}]    &&& 2.5 &&& 5.4  &&& 3.7  &&&
2.1   &&& 6.6 \\ 
{\rm HN^{13}C}  &&   [10^{11}]    &&& 4.4 &&& 7.6 &&& 6.3 &&&  5.5
&&& 13.8 \\ 
{\rm H^{13}CO^+}  &&  [10^{11}]   &&& 4.0 &&& 5.8  &&& 3.7   &&& 
8.6 &&& 4.6 \\ 
{\rm SO}    &&   [10^{13}]   &&& 1.8 &&& 1.0   &&& 1.0
  &&& 0.7 &&&  1.0\\ 
{\rm NH_3}~^a  && [10^{14}]   &&& 18  &&&  - &&& 
9.9 &&& - &&& 22  \\ 
\par
\hline  
	\end{array} 
$$
\begin{list}{}{}    
\item[$^a$] From TW; velocity components of the cores in the head  are not resolved. 
\end{list} 
   \end{table}