Galaxy groups in the 2dF Galaxy Redshift Survey: the number density of groups

Eke, V. R.; Baugh, C. M.; Cole, Shaun; Frenk, Carlos S.; Navarro, Julio F.

doi:10.1111/j.1365-2966.2006.10568.x

Cited by 67 publications

(107 citation statements)

References 68 publications

(98 reference statements)

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“…In the ¼ 2 model, there is an upturn of the mass-to-light ratio of early types around M u ¼ 3 ; 10 11 h À1 M (for those measured in other bands, see Yang et al 2003;Eke et al 2006), which means that the star formation in galaxies is strongest at this mass scale. A fitting formula for the mass-to-light ratio can be derived from…”

Section: Simulation and Halo Findingmentioning

confidence: 99%

A Subhalo‐Galaxy Correspondence Model of Galaxy Biasing

Kim

Park

Choi

2008

Astrophysical Journal

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We propose a model for allocating galaxies in cosmological N-body simulations. We identify each subhalo with a galaxy and assign luminosity and morphological type, assuming that the galaxy luminosity is a monotonic function of the host subhalo mass. Morphology is assigned using two simple relations between the subhalo mass and galaxy luminosity for different galaxy types. The first uses a constant luminosity ratio between early-type ( E/SO) and late-type (S/Irr) galaxies at a fixed subhalo mass. The other assumes that galaxies of different morphological types but equal luminosity have a constant ratio of subhalo mass. We made a series of comparisons of the properties of these mock galaxies with those of SDSS galaxies. The resulting mock galaxy sample is found to successfully reproduce the observed local number density distribution except in high-density regions. We study the luminosity function as a function of local density, and find that the observed luminosity functions in different local density environments are overall well reproduced by the mock galaxies. A discrepancy is found at the bright end of the luminosity function of early types in the underdense regions and at the faint end of both morphological types in very high density regions. A significant fraction of the observed earlytype galaxies in voids seem to have undergone relatively recent star formation and become brighter. The lack of faint mock galaxies in dense regions may be due to the strong tidal force of the central halo, which destroys less massive satellite subhalos around the simulation. The mass-to-light ratio is found to depend on the local density in a way similar to that observed in the SDSS sample. We have found an impressive agreement between our mock galaxies and the SDSS galaxies in the dependence of central velocity dispersion on the local density and luminosity.

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Section: Simulation and Halo Findingmentioning

confidence: 99%

A Subhalo‐Galaxy Correspondence Model of Galaxy Biasing

Kim

Park

Choi

2008

Astrophysical Journal

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“…This success reflects the fact that simulations of this kind make it possible to construct mock surveys where the simulated galaxy population is "observed" with a virtual telescope to produce a sample in which galaxy properties and the large-scale structure can be compared directly with those observed in real surveys (see Fig.3). Such comparisons can be used to test the effectiveness of observational procedures for identifying galaxy groups and clusters and for measuring their masses [102][103][104]. They also brings to light both inadequacies in the galaxy formation modelling [96,98] and, potentially, discrepancies with the underlying ΛCDM paradigm.…”

Section: Putting In the Galaxiesmentioning

confidence: 99%

Dark matter and cosmic structure

2012

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The current standard model for the evolution of cosmic structure is reviewed, tracing its development over the last forty years and focussing specifically on the role played by numerical simulations and on aspects related to the nature of dark matter. PreambleThe development of a standard model of cosmological structure formation over the last forty years must count as one of the great success stories in Physics. The model describes the geometry and material content of the Universe, explaining how structure -galaxies of various sizes and types, groups and clusters of galaxies, the entire cosmic web of filaments and voids -emerged from a hot and near-uniform Big Bang. This astonishing richness appears to have grown from quantum zero-point fluctuations produced during a period of cosmic inflation occurring very soon after the beginning of our Universe. Over the subsequent 13.7 billion years, these small density perturbations were amplified by the relentless action of gravitational forces due predominantly to dark matter, but illuminated by complex astrophysical phenomena involving ordinary matter. In the standard model, the dark matter, which makes up five sixths of all matter, is hypothesised to be a weakly interacting non-baryonic elementary particle, created in the early stages of cosmic evolution.In this article we will review the standard model of cosmic structure formation, focusing on the nonlinear processes that transformed the near-uniform universe that emerged from the Big Bang into the highly structured world we observe today. We will highlight the critical role that computer simulations have played in understanding this transformation, emphasizing gravitational phenomena associated with the dark matter, and only rather briefly discussing the crucially important, but more complex, processes that shape the directly observable baryonic components. Rather than presenting a complete and thorough review of the literature, our intention is to provide an account of the main ideas and advances that have shaped the subject. We begin by presenting in Table 1 a chronological listing of the landmark developments that have driven this remarkable story.

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“…As groups observed by Eke et al (2004Eke et al ( , 2006 are typically much further away, these groups are not expected to show significant redshift asymmetry. In our groups the distance ratio of the far side of the group relative to the front side of the group can be rather large, and this causes the interesting effects that are discussed next.…”

Section: Comparison With Observationsmentioning

confidence: 93%

“…However, before explaining these asymmetries we briefly compare our results to the findings of other authors. Eke et al (2004Eke et al ( , 2006) have previously applied the same method to galaxy groups identified in the 2dFGR Survey. These groups are typically much further away than our groups, as the median redshift of their groups is 0.11.…”

Section: Comparison With Observationsmentioning

confidence: 99%

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The origin of redshift asymmetries: how ΛCDM explains anomalous redshift

Niemi

Valtonen²

2008

A&A

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Aims. Several authors have found a statistically significant excess of galaxies with higher redshifts relative to the group centre, socalled 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. Methods. 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. Results. 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. Conclusions. 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.

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Galaxy groups in the 2dF Galaxy Redshift Survey: the number density of groups

Cited by 67 publications

References 68 publications

A Subhalo‐Galaxy Correspondence Model of Galaxy Biasing

A Subhalo‐Galaxy Correspondence Model of Galaxy Biasing

Dark matter and cosmic structure

The origin of redshift asymmetries: how ΛCDM explains anomalous redshift

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