Superclusters-Void Network

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Superclusters-Void Network

• Jaan Einasto
• With Maret Einasto, Enn Saar, Erik Tago, Gert
  Hütsi, Juhan Liivamägi, Ivan Suhhonenko, Mihkel
  Jõeveer, Volker Müller, Alexander Knebe, Douglas
  Tucker
• Tartu 26.02.2007

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Overview

• Distribution of galaxies and clusters
• Superclusters in the 2d Field and Sloan redshift
  surveys
• Luminosity and multiplicity functions of
  superclusters
• Wavelet analysis of the density field
• Evolution of the Supercluster-Void network
• Conclusions

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Looking for galaxy systems
Distribution of galaxies (dots) and Abell
clusters (filled circles) in the Perseus region
(Joeveer, Einasto 1977). Galaxies and clusters
populate identical regions (superclusters),
regions between superclusters almost void of
galaxies.
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Supercluster-void network 2dF data
The cosmic web 2dF Northern and Southern regions
contain filamentary superclusters of various
richness and voids
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Supercluster-void network SDSS data
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Rich superclusters
High- and low-resolution view of the richest
supercluster in 2dF Northern part. Large number
of compact density knots (DF-clusters) are
visible
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Luminosity function
Note the difference between real and simulated
superclusters
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Supercluster richness (multiplicity function)
Supercluster richness is defined as the number of
rich clusters of galaxies in the supercluster
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Cosmic web left Millennium simulation Right
2dF North Real Universe has more very rich
supeclusters than predicted by current models.
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Understanding differences between models and data

• Real data show the presence of more rich
  superclusters than predicted by models.
• To understand the difference we made a
  decomposition of the density field using wavelet
  technique.
• Wavelet analysis shows how density waves of
  different scales contribute to the present
  distribution of galaxies, clusters, superclusters
  and voids

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Left Northern SDSS slice Right The same field
but phases randomized There are no filaments,
clusters superclusters Groups galaxies
located randomly Phases are crucial to generate
Supercluster-void network
N2
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Characteristic scale 512 256 128
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64 32 2dF Original
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LCDM 256 Mpc/h Evolution of a large (w6) wave
z 0, z 1 z 2, z 5, z
10 Positions of maxima do not change Amplitudes
increase Standing wave
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LCDM 256 Mpc/h Evolution of a medium (w4) wave
z 0, z 1 z 2, z 5, z
10 Positions of maxima change little. The
increase of the amplitude depends on the location
in respect to large waves near large scale
maxima the increase is greater than near minima.
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Numerical experiment of the role of waves of
different length
Structure of models where large waves are
cut Filaments are created by medium waves,
superclusters by large waves
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Density evolution in under- and over-density
regions
In under-density regions the density continuously
decreases, in over-density regions in increases
until collapses this is formation of galaxies,
sheets and chains. The collapse (and void
emptifying) is the more rapid the higher is the
over(under)-density.
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Evolution of the supercluster-void network
Left superclusters-filaments-voids at z2 right
at z0. Contours separate high-, medium and
low-density regions using low-resolution density
field (Epanechnikov kernel of 8 Mpc radius). In
supercluster regions matter contracts and forms
rich galaxy systems, in void regions matter
expands and very few dwarf galaxies form. We
define superclusters as galaxy systems in
high-density regions. Filaments in medium-density
regions often continue supercluster filaments.
The fraction of matter in supercluster regions is
50 .
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Conclusions

• Superclusters form in regions where large density
  waves combine in similar high-density phases
• Superclusters are the richer the larger is the
  wavelength of phase synchronization
• Voids form in regions where large density waves
  combine in similar low-density phases
• But there are more very rich superclusters than
  models predict
• Large perturbations evolve very slowly and
  represent the fluctuation field at the epoch of
  inflation
• The difference between observations and models
  can be explained in two ways
• Large-scale perturbations are not incorporated in
  models, i.e. Models need improvement
• There were presently unknown processes during
  the inflation epoch