Comparing galaxy populations in compact and loose groups of galaxies

Abstract

We perform a comparison of the properties of galaxies in compact groups, loose groups and in the field to deepen our understanding of the physical mechanisms acting upon galaxy evolution in different environments. We select samples of galaxies in compact groups identified by McConnachie et al., loose groups identified by Zandivarez and Martinez, and field galaxies from the Sloan Digital Sky Survey. We compare properties of the galaxy populations in these different environments: absolute magnitude, colour, size, surface brightness, stellar mass and concentration. We also study the fraction of red and early type galaxies, the luminosity function, the colour-luminosity and luminosity-size relations. The population of galaxies in compact groups differ from that of loose groups and the field. The fraction of read and early type galaxies is higher in compact groups. On average, galaxies in compact groups are systematically smaller, more concentrated and have higher surface brightness than galaxies in the field and in loose groups. For fixed absolute magnitude, or fixed surface brightness, galaxies in compact groups are smaller. The physical mechanisms that transform galaxies into earlier types could be more effective within compact groups given the high densities and low velocity dispersion that characterise that particular environment, this could explain the large fraction of red and early type galaxies we found in compact groups. Galaxies inhabiting compact groups have undergone a major transformation compared to galaxies that inhabit loose groups.