Query : 2009A&A...494..857N

2009A&A...494..857N - Astronomy and Astrophysics, volume 494, 857-865 (2009/2-2)

The origin of redshift asymmetries: how ΛCDM explains anomalous redshift.


Abstract (from CDS):

Several authors have found a statistically significant excess of galaxies with higher redshifts relative to the group centre, so-called discordant redshifts, in particular in groups where the brightest galaxy, identified in apparent magnitudes, is a spiral. Our aim is to explain the observed redshift excess. We use a semi-analytical galaxy catalogue constructed from the Millennium Simulation to study redshift asymmetries in spiral-dominated groups in the Λcold dark matter (ΛCDM) cosmology. We create two mock catalogues of galaxy groups with the Friends-of-Friends percolation algorithm to carry out this study. We show that discordant redshifts in small galaxy groups arise when these groups are gravitationally unbound and the dominant galaxy of the group is misidentified. About one quarter of all groups in our mock catalogues belong to this category. The redshift excess is especially significant when the apparently brightest galaxy can be identified as a spiral, in full agreement with observations. On the other hand, the groups that are gravitationally bound do not show a significant redshift asymmetry. When the dominant members of groups in mock catalogues are identified by using the absolute B-band magnitudes, our results show a small blueshift excess. This result is due to the magnitude limited observations that miss the faint background galaxies in groups. When the group centre is not correctly identified it may cause the major part of the observed redshift excess. If the group is also gravitationally unbound, the level of the redshift excess becomes as high as in observations. There is no need to introduce any ``anomalous'' redshift mechanism to explain the observed redshift excess. Further, as the Friends-of-Friends percolation algorithm picks out the expanding parts of groups, in addition to the gravitationally bound group cores, group catalogues constructed in this way cannot be used as if the groups are purely bound systems.

Abstract Copyright:

Journal keyword(s): galaxies: clusters: general - galaxies: distances and redshifts - methods: N-body simulations - methods: numerical - cosmology: large-scale structure of Universe

Simbad objects: 2

goto Full paper

goto View the references in ADS

Number of rows : 2
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 NAME Virgo Cluster ClG 12 26 32.1 +12 43 24           ~ 6551 0
2 NAME Local Group GrG ~ ~           ~ 8225 0

To bookmark this query, right click on this link: simbad:objects in 2009A&A...494..857N and select 'bookmark this link' or equivalent in the popup menu


© Université de Strasbourg/CNRS

    • Contact