6 Discussion and conclusion

We started a project whose main goal is the determination of the cluster Luminosity Function and its relation to the cluster morphology and population. In this paper we describe the procedure used for the analysis of the data using A496 as a test case. The LF of this cluster has been published in Molinari et al. (1998).

In the present study, examination of the space distribution of the blue galaxies reveals a density peak at about a core radius $\sim 500$ arcsec ($\sim 0.22$ Mpc) from the cluster centre. This finding should be related to observation of a blueing of the galaxy population, beginning from the cluster centre to its outskirts (Fig. 19). This phenomenon, demonstrated to be independent from the CMR relation and luminosity segregation, calls for physical differentiation in the galaxy stellar content.

Furthermore, we measure a rather blue cD halo with a remarkable North-South colour asymmetry. This is different from what has been found, e.g., by Molinari et al. (1994) who ascribed the very red cD halo was to a M0-like stellar population, implying that any model deserves further consideration.

Further work is planned to look for these interesting features in other clusters and a detailed discussion on the above results will be given in a forthcoming paper of this series.

Acknowledgements

Thanks are due to K. Sheldt and E. Moretti for some help with English and to CARIPLO Foundation for partial funding.