SDSS-DR8 groups and clusters of galaxies

We add environmental parameters to our catalogue, together with other galaxy parameters (e.g., morphology), missing from our previous catalogues. We use a modified friends-of-friends (FoF) method with a variable linking length in the transverse and radial directions to eliminate selection effects and to find reliably as many groups as possible to track the supercluster network.

We use the groups of galaxies as a basis to determine the luminosity density field. We take into account various selection effects caused by a magnitude limited sample. Our final sample contains 576493 galaxies and 77858 groups.