Volume 545, September 2012
|Number of page(s)||10|
|Section||Cosmology (including clusters of galaxies)|
|Published online||14 September 2012|
Environments of galaxies in groups within the supercluster-void network
1 Tuorla Observatory, Department of Physics and Astronomy,
University of Turku, Väisäläntie 20, Piikkiö 21500, Finland
2 National Institute of Chemical Physics and Biophysics, 10143 Tallinn, Estonia
3 Tartu Observatory, 61602 Tõravere, Tartumaa, Estonia
Received: 5 April 2012
Accepted: 26 July 2012
Context. The majority of all galaxies reside in groups of fewer than 50 member galaxies. These groups are distributed in various large-scale environments from voids to superclusters.
Aims. The evolution of galaxies is affected by the environment in which they reside. Our aim is to study the effects of the local group scale and the supercluster scale environments on galaxy evolution.
Methods. We use a luminosity-density field to determine the density of the large-scale environment of galaxies in groups of various richnesses. We calculate the fractions of different types of galaxies in groups with richnesses of up to 50 member galaxies and in different large-scale environments from voids to superclusters.
Results. The fraction of passive elliptical galaxies rises and the fraction of star-forming spiral galaxies declines when the richness of a group of galaxies rises from two to approximately ten galaxies. On large scales, passive elliptical galaxies become more numerous than star-forming spirals when the environmental density grows to values typical of superclusters. The large-scale environment affects the level of these fractions in groups: galaxies in equally rich groups are more likely to be elliptical in supercluster environments than at lower densities. The crossing point, where the number of passive and star-forming galaxies is equal, occurs in superclusters in groups that are of lower richness than in voids. Galaxies in low-density environments need to occupy richer groups to evolve from star-forming to passive than galaxies in high-density environments. Groups in superclusters are on average more luminous than groups in large-scale environments of lower density. These results imply that the large-scale environment affects the properties of galaxies and groups.
Conclusions. Our results suggest that the evolution of galaxies is affected by both, the group in which the galaxy resides and its large-scale environment. Galaxies in lower-density regions develop later than galaxies in similar mass groups in high-density environments.
Key words: galaxies: statistics / galaxies: groups: general / large-scale structure of Universe
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.