2002A&A...394L..15B

It is shown that bright cluster dwarf ellipticals follow a relation between metallicity and apparent flattening. Rounder dwarfs tend to be more metal-rich. The evidence is based on colour as well as spectroscopic line-strength data from the literature. The large scatter of dEs around the mean metallicity-luminosity relation, usually ascribed to large observational errors, turns out to be an ellipticity effect. In the magnitude range -14>M_B>-18 the metallicity of dEs depends more strongly on ellipticity than luminosity. A possible explanation is that galaxies with masses around 10⁹M_☉ suffered a partial blowout of metal-enriched gas along their minor axis, rendering ellipticity a critical parameter for metallicity (De Young & Heckman, 1994ApJ...431..598D).