\begin{table}%t3
%\centering
\par
\caption{\label{tab:noise_frac}The estimated fraction of false-positives for each of the
three passbands using a minimum area of $\sim $$\pi (r_{\rm c}/2)^2$ and
different detection thresholds.}
\center
\begin{tabular}{cccc}
\hline\hline
Det.Thresh. & $r'$ & $z'$ & $i'$ \\
\hline 
$2.0\sigma$ & 0.61 & 0.70 & 0.73 \\
$2.5\sigma$ & 0.62 & 0.60 & 0.69 \\
$3.0\sigma$ & 0.45 & 0.44 & 0.52 \\
$3.5\sigma$ & 0.33 & 0.26 & 0.32 \\
$4.0\sigma$ & 0.18 & 0.13 & 0.18 \\
$4.5\sigma$ & 0.11 & 0.07 & 0.09 \\
$5.0\sigma$ & 0.07 & 0.04 & 0.06 \\
\hline
\end{tabular}
\end{table}