Stellar populations in dwarf elliptical galaxies: a photometrical approach

Abstract

Several constraints upon stellar populations in dwarf elliptical (dE) galaxies are derived from integrated Washington colors of a sample of 12 Fornax cluster dE's. To do so, the dE's colors are compared to observed colors of Galactic globular clusters and synthetic colors integrated from spectral energy distributions, both observed and theoretical, simple stellar populations. The position of the dwarfs in a color - color plot (C — T) vs M — Tᵢ) suggests metallicities comparable to those of moderately rich globular. However, some galaxies depart from the sequence defined by the globulars; their color can only be reproduced by a mix of an old, moderately rich dominant population, plus contribution from a younger population (∼ 5 x 10⁸ yr). The fact that one galaxy with independent evidences for a recent star formation event lies at the blue end of this sequence, strongly supports our conclusion.