Evolution of galaxies and Evolution of galaxies and
clusters in voids and clusters in voids and
superclusters superclusters
Jaan Einasto Jaan Einasto
Maret Einasto, Enn Saar, Erik Tago, Gert Hütsi, Juhan Liivamägi, Ivan Maret Einasto, Enn Saar, Erik Tago, Gert Hütsi, Juhan Liivamägi, Ivan Suhhonenko
Suhhonenko - - Tartu ObservatoryTartu Observatory Volker Müller, Alexander Knebe,
Volker Müller, Alexander Knebe, Stefan Gottlöber - AIPStefan Gottlöber - AIP Douglas Tucker
Douglas Tucker - Fermilab- Fermilab Amsterdam 14.12.2006 Amsterdam 14.12.2006
Overview Overview
Peebles question: why voids are empty? Peebles question: why voids are empty?
Numerical modeling of structure evolution; wavelet Numerical modeling of structure evolution; wavelet decomposition
decomposition
Numerical modeling: evolution in void, filament, Numerical modeling: evolution in void, filament, supercluster environment
supercluster environment
Numerical modeling: the role of perturbations of Numerical modeling: the role of perturbations of different wavelength
different wavelength
SDSS & 2dF data: voids, filaments, superclusters SDSS & 2dF data: voids, filaments, superclusters
Conclusions Conclusions
Structure of the Supercluster-void network Structure of the Supercluster-void network
Galaxies are concentrated to long essentially 1-D filaments; rich filaments form superclusters, poor filaments cross low-density regions.
Concentration of galaxies to filaments is impossible in a later epoch:
galaxies must form in filaments (Einasto, Saar, Joeveer 1977, 1980).
Evolution of under- and over-density regions
Over-densities contract until collapse, the
formation time is earlier for higher over-densities.
Forming objects have sizes ~ 1 Mpc/h
Under-densities expand,
local density decreases,
but never reaches zero
level – analytic solution by
Saar (1979)
Modeling the evolution in various Modeling the evolution in various
environment environment
Models: LCDM 256 (200) Mpc/h box, 256^3 particles, z = 10, 5, 2, 1, 0.5, 0 Density field found with 2 smoothing lengths
8 Mpc/h – global environment 0.8 Mpc/h – local environment Assumptions:
1. The mixing between large-scale environment regions is small
2. Galaxies form only there where local density exceeds the mean density 3. Unclustered matter In under-dense regions is primordial
Simulation volume is divided into 4 regions according to global density:
1. Supercluster regions, containing 30 % of matter 2. Rich filament region 30 %
3. Poor filament region 30 % 4. Void region 10 %
z = 5, z = 2 z = 1, z = 0 Main structural elements form early at z > 10 as low-density
systems, at z = 5 they have well- defined structure.
During the
evolution clusters
& filaments
merge.
Evolution of sizes of cluster particle clouds Evolution of sizes of cluster particle clouds
Clusters/groups at the present epoch were
found in high-resolution density field (41060).
Positions of cluster
particles were located at earlier epochs, and mean radii of particle clouds were found. In SCL core regions the size
decreases 5 times
(present clusters form via mergers of many
subhalos). In void region sizes do not change – groups do not evolve.
Wavelet analysis of the density field Wavelet analysis of the density field
We use the ‘a trous wavelet transform.
The field is decomposed into several frequency bands, each band contains frequencies twice the previous band, in the range ±√2 x main frequency. The sum of these bands
restores the original field.
We show the decomposition of
1) The model M256 at present epoch
2) The evolution of waves w6 and w4 from z = 10 to z = 0 3) The real density field of SDSS around SCL126
LCDM 256 Mpc/h
Evolution of w6 wave:
z = 0, z = 1 z = 2, z = 5, z = 10 Positions of maxima do not change
Amplitudes increase
Standing wave
LCDM 256 Mpc/h
Evolution of 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 maxima
increase much, near minima increase little.
Numerical experiment of the role of waves of Numerical experiment of the role of waves of different length
different length
Supercluster-void network scale is determined by largest waves present. In the absence of large &
medium scale perturbations galaxies & groups form
everywhere – there are no superclusters & filaments.
SDSS Original L=500 Mpc w2 w3 w4 w5 w6
Density perturbations as an Density perturbations as an
acoustic phenomenon acoustic phenomenon
If there exists a dominating wavelength (tone), then overtones of this wave are amplified, and intermediate waves not.
In the SDSS slice the wave 250 Mpc/h has enhanced amplitude (scale w5), its 1
stovertone (scale w4) is also amplified, as well the next 1
stovertone (scale w3).
Superclusters form in regions where large density waves Superclusters form in regions where large density waves
combine in similar high-density phases combine in similar high-density phases
Superclusters are the richer the larger is the wavelength of Superclusters are the richer the larger is the wavelength of
phase synchronization
phase synchronization
The role of waves of different wavelength The role of waves of different wavelength
Large waves form superclusters and large voids, medium waves form galaxy chains/filaments, short waves form galaxies and groups/clusters:
rich near maxima of large waves, poor near minima of large waves. No galaxy formation takes place near minima of large and medium waves, since the overall density is here below the mean density level.
Evolution of under- and over-density regions
Over-densities contract until collapse, the
formation time is earlier for higher over-densities.
Forming objects have sizes ~ 1 Mpc/h
Under-densities expand,
local density decreases,
but never reaches zero
level – analytic solution by
Saar (1979)
Conclusions I Conclusions I
Superclusters form in regions where large density Superclusters form in regions where large density waves combine in similar high-density phases
waves combine in similar high-density phases
Superclusters are the richer the larger is the Superclusters are the richer the larger is the wavelength of phase synchronization
wavelength of phase synchronization
Voids form in regions where large density waves Voids form in regions where large density waves combine in similar low-density phases
combine in similar low-density phases
Conclusions II Conclusions II
In supercluster regions the dynamical evolution is rapid, the In supercluster regions the dynamical evolution is rapid, the primordial population is consumed rapidly, and the later
primordial population is consumed rapidly, and the later
evolution consists of the transition of poor galaxy systems to evolution consists of the transition of poor galaxy systems to
rich clusters rich clusters
In void regions the mean density decreases continuously, DM-In void regions the mean density decreases continuously, DM- halos in poor filaments evolve very little, and most particles halos in poor filaments evolve very little, and most particles
remain primordial (non-clustered) remain primordial (non-clustered)
Galaxy-sized density perturbations in void regions between Galaxy-sized density perturbations in void regions between filaments
filaments had always local density below the threshold had always local density below the threshold to start galaxy formation
to start galaxy formation
In filament regions the evolution is intermediate: about one In filament regions the evolution is intermediate: about one quarter of matter is still in primordial stage, the growth of quarter of matter is still in primordial stage, the growth of
cluster population is slow, most of matter is in galaxy cluster population is slow, most of matter is in galaxy
population population..
Luminosity & multiplicity Luminosity & multiplicity
functions of 2dF, SDSS & Mill functions of 2dF, SDSS & Mill
superclusters superclusters
Left: Integrated luminosity function of 2df, SDSS & Mill simulation
superclusters. Luminosity is expressed in units of the mean luminosity of richness class 1 superclusters.
Right: Multiplicity function of observed (2dF+SDSS) superclusters, Abell cluster superclusters & Mill superclusters. Multiplicity is defined as the number of rich clusters of galaxies in the supercluster.
The number of very rich superclusters is much larger than model predicts.
LCDM z = 0: original L= 256 Mpc, w2, w3 w4, w5, w6
