\begin{table}%T4
\caption{\label{tab_mainparameter}Main parameters and their value in our simulation.  }
\small%\centering
\par
\begin{tabular}{lcccccc}
\hline\hline\noalign{\smallskip}
Stellar evolution parameters
&$\gamma$ & $\alpha_{\rm RLOF}$ & $B$ & $\beta_{\rm w}$ & $v_{\rm w}$  \\
&1.5      &             0.5    & 1000 & 1.5            &  20  \\
\noalign{\smallskip}
 & bulge & thin disc & thick disc & halo \\
\hline
age (Gyr)& 10  & 10  & 11 & 14  \\
current $M_{\rm g}$ ($M_{\odot}$) & $2\times10^{10}$   & $5.2\times10^{10}$  & $2.6\times10^{9}$ & $1\times10^{9}$ \\
current SFR ($M_{\odot}~\rm yr^{-1}$)  & 1.45 & 3.37  & single burst  & single burst\\
IMF     &  $\propto$$m^{-2.35}$   &  Eq.~(\ref{eq_imftn})  & $\propto$$m^{-1.5}$ & $\propto$$m^{-1.5}$  \\
$Z $    &   0.02   &  0.02  & 0.02 & 0.001  \\
$q $     &  flat   &  flat  & flat & flat  \\
$a $     &  Eq.~(\ref{eq_a})   &   Eq.~(\ref{eq_a})  & Eq.~(\ref{eq_a}) & Eq.~(\ref{eq_a})  \\
$P_{\rm e} $    &  $\propto$$ 2e$   &  $\propto $$2e$   & $\propto$$ 2e$  & $\propto$$ 2e$   \\
\hline 
\end{tabular}
\tablefoot{See Table~\ref{tab_densitylaws} for the Galactic structure parameters.
See Sect.~\ref{sec_model} for an explanation of the parameters.}
\end{table}