Nature and nurture of early-type dwarf galaxies in low density environments

Abstract: We study stellar population parameters of a sample of 13 dwarf galaxies located in poor groups of galaxies using high resolution spectra observed with VIMOS at the ESO-VLT. LICK-indices were compared with Simple Stellar Population models to derive ages, metallicities and [alpha/Fe]-ratios. Comparing the dwarfs with a sample of giant ETGs residing in comparable environments we find that the dwarfs are on average younger, less metal-rich, and less enhanced in alpha-elements than giants. Age, Z, and [alpha/Fe] ratios are found to correlate both with velocity dispersion and with morphology. We also find possible evidence that low density environment (LDE) dwarfs experienced more prolonged star formation histories than Coma dwarfs, however, larger samples are needed to draw firm conclusions.