DSM/DAPNIA/SAp, CEA-Saclay, 91191 Gif sur Yvette Cedex FRANCE
Ten rich galaxy clusters, with redshift ranging from 0.2 to 1., have been observed with the ISO camera in the two bands LW2 and LW3 (centered respectively at 7.5 micrometers and 15 micrometers). Objects have been analyzed by means of the CIA package and the PRETI software has been used for the detection of faint sources.
Galaxy clusters show a segregation center-outskirts: there are more detections associated to the dust (LW3 band) in the outskirts than in the central region, likely because of the greater activity in galaxies which are far from the cluster center.
In a color-magnitude diagram the ISOCAM detected sources do not occupy a particular region with respect to the other galaxies.
Therefore, the importance of ISOCAM observations comes from the fact that they allow to select galaxies which do not present peculiar optical properties, but are the best candidates to study active galaxies in a cluster.
The segregation effect, which is more clearly visible in distant cluster probably because of the effect of the K-correction, could be due to a more intense activity of galaxies or to a favorised detection of arclets as in the case of A2390 (Altieri et al, 98).
The comparison of these galaxies with these observed in the deep surveys will allow a better understanding of the galaxy evolution as a function of the environment and of the cluster age.