\begin{table}%t6
%%\centering
\par
\caption{IRAS sources in the MAMBO maps that are not detected as MAMBO   emission
  peaks. For every core in the c2d MAMBO survey the table lists   sources from the IRAS Point Source Catalogue and the IRAS Faint   Source Catalogue (preceded by an ``F''), and the subcores in which the   IRAS sources are located, if applicable. Objects from the IRAS Point   Source and Faint Source catalogues present in both catalogues are   connected. The last column gives the   spectral index between 12 and $25~\rm \mu m$   wavelength.}\label{tab-survey:IRAS_not-detected}
%\centerline
 {\small \begin{tabular}{llll}
\hline \hline\noalign{\smallskip}
 Core & IRAS source & Asso. &
$\alpha^{25~\rm \mu m}_{12~\rm \mu m}$\\
\hline
L1521--2 &   F04262+2654  & C1 & $ 0.27 \pm 0.43 $\\
L1524--4 &  04274+2420  & & $ -0.85 \pm 0.27 $\\
 &  $\lfloor$ F04274+2420  & & $ -0.83 \pm 0.19 $\\
B18-1 &  04292+2427  & & $<$--1.5  \\
 &  $\lfloor$ F04291+2427  & & $ <$--1.9 \\
TMC-2 &  04294+2413  & &  --$0.9 \pm 0.15 $\\
 &  $\lfloor$ F04294+2413  & & $ -0.89 \pm 0.11 $\\
B18-4 &  04326+2405  & C1 & $<$--1.68 \\
 &  $\lfloor$ F04326+2405  & & $<$--0.75\\
TMC-1C &  04380+2553  & &  --$0.51 \pm 0.15 $\\
 &  $\lfloor$ F04380+2553  & &  --$0.76 \pm 0.12 $\\
TMC-1 &   F04383+2549  & & $<$--1.12 \\
 &  04392+2529  & & $  $\\
L1582A &   F05290+1229  & & --$0.51 \pm 0.17 $\\
L1622A &  05517+0151  & &  --$2.14 \pm 0.16 $\\
 &  $\lfloor$ F05517+0151  & & --$2.25 \pm 0.15 $\\
 &  05519+0148  & [C2] & $  $\\
 &  05519+0157  & & $  $\\
L438 &  18116$-$0707  & & $ <$--1.33 \\
L492 &  18130$-$0341  & & $  $\\
 &  18132$-$0350  & &  --$1.82 \pm 0.15 $\\
CB188 &  19180+1127  & & $ <$--1.31\\
L675 &  19217+1103  & & $ -1.81 \pm 0.25 $\\
L1148 &  20395+6714  & & $  $\\
 &  20410+6710$^a$  & C2 & $  $\\
L1228 &   F20598+7728  & &  --$0.26 \pm 0.34 $\\
L1103-2 &  21399+5632  & & $>$--1.47\\
L1251A &   F22282+7454  & & $<$--2.54 \\
\hline
\end{tabular}}
\medskip
  $^ a$ Probably an artifact since no corresponding Spitzer source exists.
\end{table}