Environmental Dependence of Properties of Galaxies in the Sloan Digital Sky Survey

We investigate the dependence of physical properties of galaxies brighterthan M_r=-18.0 in the SDSS on environment, as measured by local density usingan adaptive smoothing kernel. We find that variations of galaxy properties withenvironment are almost entirely due to the dependence of morphology andluminosity on environment. Because galaxy properties depend not only onluminosity but also on morphology, it is clear that galaxy properties cannot bedetermined solely by dark halo mass. When morphology and luminosity are fixed,other physical properties, such as color, color-gradient, concentration, size,velocity dispersion, and star formation rate, are nearly independent of localdensity. The only feature is the sharp decrease of late type fraction above thecritical luminosity of about M_r=-21.3 in the morphology versus luminosityrelation. Weak residual dependences on environment include that of the color oflate-types (bluer at lower density) and of the L-sigma relation of early-types(larger dispersion at higher density for bright galaxies). The early-typefraction is a monotonically increasing function of local density andluminosity. The morphology-density- luminosity relation should be a keyconstraint on galaxy formation models. We demonstrate that the dependence onenvironment of the morphology of galaxie originates from variations in densityon effective Gaussian smoothing scales much smaller than 12 h^{-1}Mpc. We findthat galaxy morphology varies both with density measured on an effectiveGaussian smoothing scale of 4.7 h^{-1} Mpc and on distance to the nearestbright galaxy (particularly, for about 0.2 h^{-1}Mpc). We propose a mechanismthat the morphology of galaxies in galaxy systems is transformed by the tidalforce.Comment: typos corrected, matched to the published versio