\begin{table}%t1
%\centering
\par
\caption{\label{tab:constraint_comparisons}Free parameters that affect the evolution of the baryonic Universe, see Sect.~2.3 for more details.}
\small \begin{tabular}{cccc}
\hline \hline
Parameter & Description   & Fiducial value & Source of constraints\\
\hline  
$\beta$  & Inverse of star formation efficiency  & 50& Kennicutt (1998)\\
$\epsilon$  & Inverse of mass loading for feedback    & 0.1         & \citet{Martin2002}\\
$\chi$      & Galaxy merger power law    & 3.333 & Numerical simulations e.g. Walker et~al. (1996)\\
\hline
$\Omega_B$  & Baryon fraction  & 0.02~h$^{-2}$  & $^2$H abundance in QSO absorption lines \citep{Tytler1996}\\
$\psi$ & S-S merging normalisation & 0.017  & \citet{Makino1997}\\
$\varsigma$ & Recycling efficiency   & 0.3     & Set to fiducial value in Hatton et~al. (2003)\\
$\kappa$ & Ratio of burst-to-bulge radius  & 0.1 & Set to fiducial value in Hatton et~al. (2003)\\
Dust & ISM Extinction and emission due to dust & -- & Guiderdoni et~al. (1987), Desert et~al. (1990)\\
IMF & Initial mass function  & --  & \cite{Kennicutt1983}\\
\hline
\end{tabular}
\end{table}