We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey ( 2dFGRS ) observed areas and have identified 431 Abell , 173 APM and 343 EDCC clusters .
Precise redshifts , velocity dispersions and new centroids have been measured for the majority of these objects , and this information has been used to study the completeness of these catalogues , the level of contamination from foreground and background structures along the cluster ’ s line of sight , the space density of the clusters as a function of redshift , and their velocity dispersion distributions .
We find that the Abell and EDCC catalogues are contaminated at the level of about 10 % , whereas the APM catalogue suffers only 5 % contamination .
If we use the original catalog centroids , the level of contamination rises to approximately 15 % for the Abell and EDCC catalogues , showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues .
There is a deficiency of clusters at z \sim 0.05 that may correspond to a large underdensity in the Southern hemisphere .
From the cumulative distribution of velocity dispersions for these clusters , we derive an upper limit to the space density of \sigma > 1000 { km s ^ { -1 } } clusters of 3.6 \times 10 ^ { -6 } h ^ { 3 } { Mpc } ^ { -3 } .
This result is used to constrain models for structure formation ; our data favour low-density cosmologies , subject to the usual assumptions concerning the shape and normalization of the power spectrum .