\begin{table}%t1
%\centering
\par
\caption{Basic data for \object{I Zw 1}.}
\label{tab:zwdata}
\begin{tabular}{lll}
	\hline\hline
	\noalign{\smallskip}
	${\rm RA}_{2000}$ & ${\rm 00h53m34.9s}$ 
	& \citet{1999PASP..111..438F} \\
	${\rm Dec}_{2000}$ & $+12d41\arcmin 36\arcsec$ 
	& \citet{1999PASP..111..438F}\\
	${\rm Position\ Angle} $& $135\degr$  
	& \citet{1998ApJ...500..147S}\\
	${\rm Inclination}$ & $(38\pm 5)\degr $ 
	& \citet{1998ApJ...500..147S}\\
	${\rm Redshift}$ & 0.0611 &\citet{1997ApJ...478..144S}\\
	${\rm Distance}$ & $242\ {\rm Mpc}^{{\rm a}}$ & \\
	${\rm Length\ Conversion\ Factor} $
	& $1 \arcsec \approx 1.2\ {\rm kpc}$ & \\
	\noalign{\smallskip}
	\hline\noalign{\smallskip}
	\multicolumn{3}{l}{$^{{\rm a}}$ $H_0=75$~km~s$^{-1}$~Mpc$^{-1}$ and 
	$q_0=0$ will be adopted throughout the}\\
	 paper.
\end{tabular}
\par
\end{table}