The properties of galaxy groups from the luminous red galaxies (LRGs) of SDSS DR6

Using an approximately volume-limited LRG sample of SDSS DR6, we investigate the basic properties of groups identified by Berlind et al. [A.A. Berlind, J. Frieman, D.H. Weinberg, et al., ApJS 167 (2006) 1] 's algorithm and Davis et al. [M. Davis, G. Efstathiou, C.S. Frenk, S.D.M. White, ApJ 292 (1985) 371]'s algorithm, respectively. It is found that the basic properties of groups strongly depend on the values of the linking parameters. Different group samples have mean physical parameters which are rather different. We may confess that there is no values for the linking lengths that will work perfectly for every sample. In addition, we note that the luminosity distribution of member galaxies of groups identified by different algorithms is nearly the same, but member galaxies of groups identified using the linking lengths b⊥=0.14, b//=0.75 have a higher proportion of red galaxies and a lower proportion of blue galaxies than member galaxies of groups identified using the linking length b = 0.2.