\begin{table}%t3
\caption{\label{tcolumn}ortho-\HTDP column densities.}
\small%\centerline
 {
\begin{tabular}{lcccccccc}
\hline\hline
%&&&&&&&& \\[-8pt]
Source & $n$(\MOLH) & $T_{\rm kin}$ & Ref.$^{{a}}$ & $N$(\MOLH)$^{{b}}$ & Ref. &
         $T_{\rm ex}$$^{{c}}$ & $\tau$$^{{c}}$ &
         $N$(ortho-\HTDP)$^{{c}}$ \\
name   & (\percc ) & (K) &  & (10$^{22}$ \cmsq) & & (K) &  &
         (10$^{13}$ \cmsq ) \\
\hline
\multicolumn{9}{c}{Starless Cores} \\
L~1498            & 1 $\times$ 10$^5$ & 10    & 4   & 3.2 & 7
                 & 7.5, 5.5 & $<$0.3, $<$0.9 & $<$0.7, $<$2 \\
TMC-2           & 3 $\times$ 10$^5$ & 10$^{{d}}$ & 7 & 6.0 &
                   7 & 8.7, 5.9 & $<$0.2, $<$0.6 & $<$0.5, $<$1.5 \\
TMC-1C          & 1 $\times$ 10$^6$ & 7 & 8, 9 & 8.5 & 9 &
                   6.8, 6.0 & 0.4, 0.6 & 0.9, 1.4\\
L~1517B           & 2 $\times$ 10$^5$ & 9.5 & 4 & 3.7 & 7 &
                   8.0, 5.6 & 0.2, 0.9 & 0.4, 1.8 \\
L~1544            & 2 $\times$ 10$^6$ & 7 & 21  & 13 & 7$^{{i}}$ &
                   6.9, 6.5 & 1.2, 1.7 & 3.2, 4.5 \\
L~183             & 2 $\times$ 10$^6$ & 7     & 12, 22 & 14 & 12 &
                   6.9, 6.5 & 1.1, 1.6 & 2.5, 3.5 \\
Oph~D           & 5 $\times$ 10$^5$ & 7 & 23 & 11 &
                   23 & 6.7, 5.8 & 0.8, 2.0 & 1.6, 4.0 \\
B~68$^{{e}}$  & 3 $\times$ 10$^5$ & 10 & 24, 13 & 1.4 & 7 &
                   8.7, 5.9 & 0.1, 0.3 & 0.2, 0.5 \\
L~429             & 6 $\times$ 10$^5$ & 7$^{{d}}$ & 7 & 12 &
                   7$^{{i}}$ & 6.8, 6.3 & 1.1, 1.8 & 4.1, 6.7 \\
L~694-2          & 9 $\times$ 10$^5$ & 7$^{{d}}$ & 7 & 11 &
                   7$^{{i}}$ & 6.9, 6.3 & 1.1, 2.0 & 3.2, 5.7 \\
16293E$^{{f}}$ & 2 $\times$ 10$^6$ & 12 & 19 & 50 & 19 &
                   12, 10 & 0.5, 0.7 & 1.2, 1.7 \\
\hline
\multicolumn{9}{c}{Protostellar Cores} \\
NGC 1333 DCO$^+$ & 1 $\times$ 10$^6$$^{{d}}$       & 13    & 1   & 31 & 14 &
                   12, 8.7 & 0.03, 0.1 & 0.35, 0.59 \\
B~1               & 3 $\times$ 10$^6$ & 12    & 2, 3 & 21 & 15 &
                   12, 10 & 0.1, 0.1 & 0.9, 1.1 \\
IRAM~04191        & 5 $\times$ 10$^5$ & 10    & 5   & 17 & 16 &
                   9.2, 6.8 & $<$$0.3$, $<$$0.6$ & $<$$0.8$, $<$$1.5$ \\
L~1521F           & 1 $\times$ 10$^6$ & 9.3  & 6, 20  & 14 &
                   7 & 8.9, 7.3 & 0.2, 0.4 & 0.7, 1.1 \\
Ori~B9$^{{g}}$ & 7 $\times$ 10$^4$ & 10 & 10 & 4.0 & 10 &
                   6.8, 4.2 & 0.1, 0.4 & 0.2, 0.9 \\
NGC~2264G-VLA2   & 8 $\times$ 10$^5$ & 15    & 11  & 10 & 17 &
                   14, 9.2 & 0.1, 0.2 & 0.3, 0.5 \\
NGC 1333 IRAS 4A$^{{h}}$ & 2 $\times$ 10$^6$ & 13 & 18 & 31 & 18 &
                   13, 10 & 0.03, 0.04 & 0.2, 0.3 \\
\hline
\end{tabular}}
\medskip
$^{{a}}$ When more than one reference is listed, the first number refers to the source paper for the volume density and the second number refers to the source paper for the kinetic temperature. In the case of L~183,  both parameters can be found in the two listed papers. \\
$^{{b}}$ Values of $N$(\MOLH) have been estimated assuming a constant gas temperature of 10~K along the line of sight, except for those objects with central temperatures of 7~K (see item~``$i$'' below). \\  
$^{{c}}$ The first value is calculated assuming a critical density $n_{\rm cr}$~= 10$^5$~\percc,
whereas the second value is for $n_{\rm cr}$~= 10$^6$~\percc. \\
$^{{d}}$ Assumed value. \\
$^{{e}}$ Ortho-\HTDP \ data from \citet{hce06}, but method described in the text. \\
$^{{f}}$ Ortho-\HTDP data from \citet{vpy04}, but method described in the text. \\
$^{{g}}$ Estimates of $T_{\rm ex}$, $\tau$ and $N$(ortho-\HTDP) based on APEX data from \citet{hhl06},  but using the method described in the text. \\
$^{{h}}$ Data from \citet{svv99}, but method described in the text. \\
$^{{i}}$ The value of $N$(\MOLH) given by \citet{ccw05} has been modified to take into account the temperature gradient (see Sect.~\ref{scolumn} for details). \\ 
References: (1) \citet{h03}; (2) \citet{lgr06};
(3) \citet{mcr05}; (4) \citet{tmc04}; (5) \citet{ba04}; (6)~\citet{ccw04};
(7) \citet{ccw05}, in a 11\arcsec \ beam; (8) \citet{sg05}; (9) \citet{skg07}; 
(10) \citet{hww93}, in a 40\arcsec \ beam; (11) \citet{geh00}; 
(12) \citet{pbm04}; (13) \citet{hhj02};
(14) \citet{vsm02}, in a 13\arcsec \
beam; (15)~\citet{hrf05}, in a 14\arcsec\ beam; (16) \citet{bad02},
in a 11\arcsec \ beam; (17) \citet{gct94}, within 20\arcsec ;
(18) \citet{svv99} ($N$(\MOLH) measured in a 13\arcsec \ beam);
(19) \citet{vpy04} ($N$(\MOLH) measured in a 13\arcsec \ beam
using \citealt{lgp02} data); (20) \citet{kwa07}; (21) \citet{ccw07};
(22) \citet{pbc07}; (23) \citet{sww07}; (24) \citet{bmv06}.
\end{table}