Volume 439, Number 1, August III 2005
|Page(s)||45 - 58|
|Section||Cosmology (including clusters of galaxies)|
|Published online||22 July 2005|
Toward understanding environmental effects in SDSS clusters
Tartu Observatory, 61602 Tõravere, Estonia e-mail: firstname.lastname@example.org
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
Accepted: 5 April 2005
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 ∼25. We see similar effects in numerical simulations – simulated clusters in a high-density environment are ~ 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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