Effects of both extremes of environments on galaxy properties

Aims. We investigate the dependence of galaxy properties on the local environment. Methods. Member galaxies of compact groups (CGs) and isolated galaxies are located at both extremes of density, which are identified from the volume-limited Main galaxy sample of the Sixth Data Release of the Sloan Digital Sky Survey(SDSS DR6), while the volume-limited Main galaxy sample represents the mean density. We perform comparative studies of distributions of various physical properties among member galaxies of CGs, isolated galaxies, and the volume-limited Main galaxy sample. Results. We find that physical properties of galaxies, such as luminosity, size, colors, concentration index, and morphology strongly depend on the local environment: luminous, red, and early-type galaxies exist preferentially in the densest regions of the universe (e.g., in groups), while faint, blue, and late-type galaxies are located preferentially in low-density regions.