  We study the differences and similarities in the luminosities of bound,
infalling and the so-called backsplash (Gill et al. 2005) galaxies of the Milky
Way and M31 using a hydrodynamical simulation performed within the Constrained
Local UniversE Simulation (CLUES) project. The simulation models the formation
of the Local Group within a self-consistent cosmological framework. We find
that even though backsplash galaxies passed through the virial radius of their
host halo and hence may have lost a (significant) fraction of their mass, their
stellar populations are hardly affected. This leaves us with comparable
luminosity functions for infalling and backsplash galaxies and hence little
hope to decipher their past (and different) formation and evolutionary
histories by luminosity measurements alone. Nevertheless, due to the tidal
stripping of dark matter we find that the mass-to-light ratios have changed
when comparing the various populations against each other: they are highest for
the infalling galaxies and lowest for the bound satellites with the backsplash
galaxies in-between.
