Dwarf elliptical galaxies

AbstractDwarf elliptical (dE) galaxies, with blue absolute magnitudes typically fainter thanMB=−16, are the most numerous type of galaxy in the nearby universe. Tremendous advances have been made over the past several years in delineating the properties of both Local Group satellite dE's and the large dE populations of nearby clusters. We review some of these advances, with particular attention to how well currently available data can constrain(a)models for the formation of dE's(b)the physical and evolutionary connections between different types of galaxies (nucleated and nonnucleated dE's, compact E's, irregulars, and blue compact dwarfs) that overlap in the same portion of the mass-spectrum of galaxies(c)the contribution of dE's to the galaxy luminosity functions in clusters and the field(d)the star-forming histories of dE's and their possible contribution to faint galaxy counts, and(e)the clustering properties of dE's. In addressing these issues, we highlight the extent to which selection effects temper these constraints, and outline areas where new data would be particularly valuable.