\begin{table}%t3
\caption{\label{5arm}The parameters of the polynomial logarithmic arm model.}
%\centering
\par
\begin{tabular}{cccccc}
\hline
\hline
$i$th arm & $a_i$ & $b_i$ & $c_i$ & $d_i$ & $\theta_i$ \\
\hline
&&&&& \\[-8pt]
\multicolumn{5}{l}{For distribution with $R_{0}=8.5$~kpc and $\Theta_{0}=220$~km s$^{-1}$}& $(^{\circ})$\\
arm-1& 1.376 & --0.07792 & 0.04309 & 0 &41 \\
arm-2&7.330 & --2.302 & 0.2849 & --0.01059 &304   \\
arm-3&10.403 & --3.526 & 0.4620 & --0.01895 &298   \\
arm-4& 1.978 & --0.1181 & 0.02098 & 0 &338 \\
arm-5&2.297 &0.09116 &0.04273 & 0 &35\\
$Z$&0.31   &   &    &     &\\
\hline
&&&&& \\[-8pt]
\multicolumn{5}{l}{For distribution with $R_{0}=8.0$~kpc and $\Theta_{0}=220$~km s$^{-1}$}& $(^{\circ})$ \\
arm-1& 1.302 & --0.06629 & 0.04115 & 0 &47 \\
arm-2&7.5616 & --2.448 & 0.3090 & --0.01187 &304  \\
arm-3&9.9843 & --3.417 & 0.4522 & --0.01873 &298    \\
arm-4& 1.5189 & --0.00581 & 0.01286 & 0 &338 \\
arm-5&2.1949 &0.1037 &0.03317 & 0 &35 \\
$Z$&0.26   &   &    &   \\
\hline
&&&&& \\[-8pt]
\multicolumn{5}{l}{For distribution with $R_{0}=8.4$~kpc and $\Theta_{0}=254$~km s$^{-1}$}& $(^{\circ})$ \\
arm-1& 1.3747 & --0.0737 & 0.04318 & 0 &41 \\
arm-2&11.2880 & --3.8678 & 0.4900 & --0.01949 &304  \\
arm-3&10.2992 & --3.519 & 0.4662 & --0.01937 &298    \\
arm-4& 1.5645 & --0.005055 & 0.0132 & 0 &338 \\
arm-5&2.2973 &0.004478 &0.0750 & 0 &55 \\
$Z$&0.29   &   &    &   \\
\hline
\end{tabular}
\end{table}