Further studies of the local environmental dependence of galaxy properties

Using the three-dimensional galaxy local density in a comoving sphere with a radius of the distance to the fifth nearest galaxy for each galaxy, we construct two samples at both extremes of density from the volume-limited Main galaxy sample of the Sixth Data Release of the Sloan Digital Sky Survey (SDSS DR6). It is found that the sample at low density has a higher proportion of faint, blue, and late-type galaxies and a lower proportion of luminous, red, and early-type galaxies than the sample at high density. We also measure the projected local density Sigma(5), which is computed from the distance to the fifth nearest neighbor within a redshift slice +/- 1000 km s(-1) of each galaxy, and come to the same conclusions. In addition, we note that there is no significant difference between the mean luminosity and the mean colors of two samples (< 1 sigma), which is consistent with the conclusion obtained by Deng and colleagues in 2007.