\begin{table}%t2
%\centering
\par
\caption{\label{models_used}Summary of the dark cloud (DC), hot core (HC) and PDR models used to model the time dependent HNCO gas-phase abundance.}
\begin{tabular}{cccll}
\hline\hline \noalign{\smallskip}
Model & $T$~(K) & $n_{{\rm H}}$~(cm$^{-3}$) & Initial chemistry & HNCO formation chemistry \\
\hline
DC1 & 10 & $2.0 \times10^{4}$ & Atomic & Reaction~c only\\
DC2 & 10 & $2.0 \times10^{4}$ & Atomic & Reactions c,d,e and f\\
DC3 & 10 & $2.0 \times10^{4}$ & Atomic & Reactions d,e,f and g\\
DC4 & 10 & $2.0 \times10^{4}$ & Atomic & Reactions c,d,e,f and g \\
HC1 & 200 & $2.0 \times10^{7}$ & CC1 & All\\
HC2 & 200 & $2.0 \times10^{7}$ & CC2 & Gas phase only\\
HC3 & 200 & $2.0 \times10^{7}$ & CC3 & Surface only (reactions a,b)\\
HC4 & 200 & $2.0 \times10^{7}$ & CC4 & All\\
HC5 & 20 & $2.0 \times10^{7}$ & CC5 & All\\
HC6 & 20 & $2.0 \times10^{7}$ & CC1 & All\\
HC7 & 50 & $2.0\times10^{7}$ & CC6 & All\\
HC8 & 50 & $2.0 \times10^{7}$ & CC1 & All\\
HC9 & 100 & $2.0 \times10^{7}$ & CC7 & All\\
HC10 & 100 & $2.0\times10^{7}$ & CC1 & All\\
PDR1 & 50 & $2.0\times10^{4}$ & Atomic & All\\
PDR2 & 50 & $2.0\times10^{4}$ & Atomic & Gas phase only\\
PDR3 & 50 & $2.0\times10^{4}$ & Atomic & Surface only (reactions a,b)\\
PDR4 & 50 & $2.0\times10^{7}$ & CC1 & All\\
PDR5 & 50 & $2.4\times10^{5}$ & CC1 & All\\
\hline
\end{tabular}
\tablefoot{$T$ is the gas-phase temperature and $n_{{\rm H}}$ is the total hydrogen number density (both held constant).  The initial chemistry was
  either~$atomic$, where all species (except H) were in their
  elemental form, or $evolved$, where abundances from a collapsed
  cloud (CC) model were used.  The collapsing cloud models are listed
  in a separate table. }
\end{table}