\begin{table}%t3
 \caption{\label{tab:2}Distance dependence of the parameters. }
 %\centering
\par
\begin{tabular}{llll}
 \hline\hline\noalign{\smallskip}
 Variable & Proportionality & \multicolumn{1}{c}{Value} & Unit \\
 \noalign{\smallskip}\hline\noalign{\smallskip}
  $D$ & $\propto$$D$  & 140 & pc\\
  $T_{100}$ &   $\propto$$D^q$ & $52 \pm 4$ & K \\
  $n_{100}$ &   $\propto$$D^s$ & $3.0\times 10^7 \pm 0.4\times 10^7$ & cm$^{-3}$ \\
  $R_{{\rm out}}$ & $\propto$$D$ & $122\pm 10$ & AU \\
  $V_{100}$ & $\propto$$D^{0.5}$ & $3.35 \pm 0.25$ & km~s$^{-1}$ \\
  $M_*$ & $\propto$$D$ & $1.32 \pm^{0.20}_{0.12}$ & $\msun$ \\
\hline
\end{tabular}
\end{table}