Groups and clusters of galaxies in the SDSS DR8

Abstract

Aims: We intend to compile a new galaxy group and cluster sampleof the latest available SDSS data, adding several parameter for thepurpose of studying the supercluster network, galaxy and group evolution,and their connection to the surrounding environment. Methods: Weused a modified friends-of-friends (FoF) method with a variable linkinglength in the transverse and radial directions to eliminate selectioneffects and to find reliably as many groups as possible. Using thegalaxies as a basis, we calculated the luminosity density field.Results: We create a new catalogue of groups and clusters for theSDSS data release 8 sample. We find and add environmental parametersto our catalogue, together with other galaxy parameters (e.g., morphology),missing from our previous catalogues. We take into account variousselection effects caused by a magnitude limited galaxy sample. Ourfinal sample contains 576 493 galaxies and 77 858 groups. The groupcatalogue is available at http://www.aai.ee/~elmo/dr8groups/ andat the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/540/A106