Compact Groups of Galaxies: Evolution of the Stellar Population

Abstract

We present a study focusing on the nature of compact groups (CGs) through the study of their elliptical (E) galaxies. Parameters describing the internal dynamics and the stellar populations of the galaxies are compared with their counterparts in other environments. Our sample has24 bright E galaxies located in the core of Hickson CGs and 11 bright ‘bona fide’ Es, located in the field or very loose groups. Their spectra were obtained with the 2.1 m Telescope at KPNO and have a 4.1 A resolution over the wavelength range 3500–7000 A. We have found that, from the dynamical point of view, E galaxies in CGs are essentially similar to those in dense clusters. Moreover, the stellar populations of Es in CGs seem to be older and less metal rich than those in the field, behaviour which has also been observed by Rose et al. (1994).