than by rotation.

The combination of low gas-mass fractions and moderate-to-low stellar metallicities in dE (about 0.1 of solar or less) is a key feature of this class. Their lower stellar abundances [@haa97] suggest that extensive gas loss occurred during their evolution and SF ceased due to a lack of raw material rather than exhaustion of the gas supply through SF. Galactic winds are therefore a hallmark of modern models for dE evolution, starting from the basic consideration by [@lar74] and continued with the study by [@ds86]. They are commonly assumed to have cleaned out DGs soon after their formation. As mentioned in sect. \[dIrrs\], however, gas expulsion by means of galactic winds is inefficient from our understanding of the multi-phase ISM and requires even in low-mass systems a DM-to-baryonic matter ratio [@mlf99] much smaller than assigned to DGs in the classical formation picture (e.g. [@mat98]).

There are two competing scenarios for the origin of cluster dEs. On the one hand, those low-mass galaxies are believed to constitute the building blocks in $\Lambda$CDM cosmology and should therefore have evolved congruently with the mass accumulation to more massive entities, galaxies and galaxy clusters. For those, orbiting in a cluster the stellar 