\begin{table}%t2
\caption{\label{table:tab2}Sample selection criteria.}
\small%\centerline
 {
\begin{tabular}{c|c}
\hline \hline
%& \\[-8pt]
Selection criteria$^{{a}} $ & Number of objects$^{{b}}$\\
\hline
$m_{4.5} \le 23$& 4142\\ 
$z_{\rm phot} \ge 3.5$ & 140\\ 
No hard X-ray emission & 125\\
IRAC/channel 4 peak & 53\\
\hline 
\end{tabular}}
\medskip
$^{{a}}$ Subsequent steps to select the final sample; 
$^{{b}}$ number of objects satisfying each criterion.
\end{table}