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Issue A&A
Volume 439, Number 1, August III 2005
Page(s) 45 - 58
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20042347



A&A 439, 45-58 (2005)
DOI: 10.1051/0004-6361:20042347

Toward understanding environmental effects in SDSS clusters

J. Einasto1, E. Tago1, M. Einasto1, E. Saar1, I. Suhhonenko1, P. Heinämäki1, 2, G. Hütsi1, 3 and D. L. Tucker4

1  Tartu Observatory, 61602 Tõravere, Estonia
    e-mail: einasto@aai.ee
2  Tuorla Observatory, Väisäläntie 20, Piikkiö, Finland
3  Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Str 1, 86740 Garching, FRG, Germany
4  Fermi National Accelerator Laboratory, MS 127, PO Box 500, Batavia, IL 60510, USA

( Received 9 November 2004 / Accepted 5 April 2005 )

Abstract
We find groups and clusters of galaxies using the Data Releases DR1 and DR3 of the Sloan Digital Sky Survey. We calculate a low-resolution density field with a smoothing length of 10 h-1 Mpc to characterise the density of the cluster environment, and a medium-resolution density field with a smoothing length of 2 h-1 Mpc to characterise the galaxy environment. We determine the luminosity function of clusters, and investigate properties of galaxies and clusters in various environments. We show that clusters in a high-density environment are about 5 times more luminous than in a low-density environment, and luminosities of galaxies in different environments differ by a factor of $\sim $25. We see similar effects in numerical simulations - simulated clusters in a high-density environment are ~100 times more massive than those in a low-density environment. Comparison of the density distribution in simulations at various epochs shows that in large low-density regions (voids) dynamical evolution is very slow and stops early. In contrast, in large regions of higher density (superclusters) dynamical evolution starts early and continues until the present; here particles cluster early, and by merging of smaller groups very rich systems of galaxies form.


Key words: large-scale structure of Universe -- galaxies: clusters: general -- dark matter




© ESO 2005


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