\begin{table}%t15
\caption{\label{t:chem-tab2}Peak gas-phase abundances from each model, with corresponding 
model temperatures, as well as source sizes, rotation temperatures, and gas-phase abundances derived from the observations of the main source in~Sgr~B2(N).}
\small%\centerline
 {
\begin{tabular}{lccccccccccc}
\hline
\hline
Species & \multicolumn{2}{c}{\textit{Basic} model} & & \multicolumn{2}{c}{\textit{Select} model} & & \multicolumn{3}{c}{Observations} & & Abundance ratio\\
\cline{2-3} \cline{5-6} \cline{8-10}
     & $n[i]/n_{{{\rm H}}_2}$ & $T^a$ & & $n[i]/n_{{{\rm H}}_2}$ & $T^a$ & & Size & $T_{\rm rot}$ & $n[i]/n_{{{\rm H}}_2}$ & & \textit{Select} model\\
     &                         & (K) & &                         & (K) & & ($\arcsec$) & (K)      &                         & & over observation \\
(1)  & (2)                     & (3) & & (4)                     & (5) & & (6)         & (7)      & (8)                     & & (9) \\
\hline
HCOOH (hot)    & 5.4e-08 & 120 & &  5.4e-08 & 120 & & 5.0 &  70 & 1.3e-09 & & 42 \\
HCOOH (cold)   & 4.9e-09 &  42 & &  4.9e-09 &  42 & & 5.0 &  70 & 1.3e-09 & &  3.8 \\
CH$_3$OCHO     & 1.7e-07 &  81 & &  1.6e-07 & 112 & & 4.0 &  80 & 3.5e-08 & &  4.6 \\
C$_2$H$_5$OCHO & 2.3e-09 & 110 & &  2.3e-09 & 110 & & 3.0 & 100 & 3.6e-09 & &  0.6 \\
C$_2$H$_5$OH   & 1.0e-07 & 120 & &  1.0e-07 & 120 & & 3.0 & 100 & 5.7e-08 & &  1.8 \\
CH$_3$OCH$_3$  & 2.3e-07 & 200 & &  2.8e-07 & 200 & & 2.5 & 130 & 1.4e-07 & &  2.0 \\
CH$_3$CN       & 6.3e-09 &  92 & &  6.8e-09 &  92 & & 2.7 & 200 & 1.3e-07 & &  0.05 \\
C$_2$H$_5$CN   & 4.4e-08 & 117 & &  3.3e-09 & 117 & & 3.0 & 170 & 8.1e-08 & &  0.04 \\
C$_3$H$_7$CN   & 3.5e-08 & 120 & &  4.0e-11 & 123 & & 3.0 & 150 & 1.0e-09 & &  0.04 \\
NH$_2$CH$_2$CN & 1.4e-08 & 117 & &  1.2e-08 & 117 & & 2.0 & 100 & 1.5e-09 & &  8.0 \\
C$_2$H$_3$CN   & 1.2e-08 & 200 & &  5.1e-08 &  92 & & 2.3 & 170 & 4.7e-08 & &  1.1 \\
\hline
\end{tabular}}
\medskip
Notes: $^a$ The model temperatures are the temperatures at which the peak gas-phase abundances are achieved.
\end{table}