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Clusters and groups of galaxies in the 2dF galaxy redshift
survey. A new Catalogue

E. Tago, J. Einasto, E. Saar, M. Einasto, I. Suhhonenko,
M. Jõeveer, J. Vennik, P. Heinämäki and D. L. Tucker
We create a new catalogue of groups and clusters, applying
the friends-of-friends method to the 2dF GRS final release. We
investigate various selection effects due to the use of a magnitude
limited sample. For this purpose we follow the changes in group
sizes and mean {\bf galaxy number densities within groups} when
shifting nearby observed groups to larger distances. We study the
distribution of sizes of dark matter haloes in $N$-body simulations
and compare properties of these haloes and the 2dF groups. We show
that at large distances from the observer luminous and intrinsically
greater groups dominate, but in these groups only very bright
members are seen, which form compact cores of the groups. These two
effects almost cancel each other, so that the mean properties of
groups do not change considerably with distance. Our final sample
contains 10750 groups in the Northern part, and 14465 groups in the
Southern part of the 2dF survey with membership $N_g \geq $ 2. We
estimate the total luminosities of our groups, correcting for group
members fainter than the observational limit of the survey. The
cluster catalogue is available at our web-site
(http://www.aai.ee/~maret/2dfgr.html).

A paper on the 2dF GRS groups with high resolution figures,
and with group and galaxy tables can be found
here

Here we show the spatial distribution of our groups:

Northern sky

Southern sky

The sizes of spheres are proportional to their virial radii.
Only groups with at least 4 member galaxies are shown.
Colors are coded according to the total luminosities
of groups.
Lumonosity limits: (in units of solar luminosities):

red > L=0.1E+12

yellow > L=0.2E+11

blue > L=0.5E+10

gray < L=0.5E+10

We present a catalogue of 2dF groups.

A catalogues
of 2dF groups, galaxies in groups and isolated galaxies

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