The galaxy luminosity function:

The faint end slope  a of the galaxy luminosity function (GLF) is a crucially important quantity to be contrasted with the slope of the dark matter halo mass function (Moore et al. 1999), in order to constrain structure formation theories.

Within our team, we have investigated the very faint end of the GLF in the Fornax, Hydra and Centaurus clusters (Hilker et al. 2003, Mieske et al. 2007, Misgeld et al. 2008 and 2009 ). For this we have adopted a hybrid approach, combining visual selection of dwarf galaxy candidates with automated object detection using SExtractor. We have also made use of the Surface Brightness Fluctuation method (Tonry & Schneider 1988) to directly confirm dwarf galaxy cluster memberships (Mieske et al. 2005 & 2007).

Our results for Fornax, Hydra and Centaurus yield a very shallow faint end slope, flatter than expected for the slope of the dark matter halo mass function.

We are continuing our efforts for a characterisation of the GLF in other environments, like fossil groups and rich clusters (PhD thesis of I. Misgeld and S. Lieder).