Families of ellipsoidal stellar systems and the formation of dwarf elliptical galaxies

Abstract

Core radii and central surface brightnesses of bulges and elliptical galaxies are measured using CCD photometry obtained with the CFH Telescope. The correlations between core parameters are derived and compared for ellipticals, bulges, dwarf spheroidal galaxies, dwarf irregular galaxies, and globular clusters. The data confirm the existence of well-defined correlations between the core parameters of elliptical galaxies. The bulges of disk galaxies are basically similar to elliptical galaxies. Ordinary and dwarf elliptical galaxies do not form a continuous sequence. Rather, bulges and ellipticals, dwarf spheroidals, and globular clusters appear to be three very distinct kinds of stellar systems. Dwarf spheroidal galaxies are most closely related to dwarf irregular galaxies and may have evolved from them.