arXiv subjects

J. Einasto

Publications and source records attributed to J. Einasto.

72 records · Page 4Linked to original sources

arXiv1999

The supercluster-void network V. Alternative evidence for its regularity

The distribution of Abell clusters of galaxies is analysed to study the regularity of the supercluster-void network. A new geometric method sensitive to the regularity of the location of clusters is applied. We find that the supercluster-void network resembles a cubical lattice over the whole space investigated. The distribution of rich superclusters is not isotropic: along the main axis of the network it is periodic with a step of length about 130 Mpc (for Hubble constant h=1), whereas along the diagonal of the network the period is larger. This large-scale inhomogeneity is compatible with recent CMB data.

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arXiv1998

Steps toward the power spectrum of matter. I.The mean spectrum of galaxies

We calculate the mean power spectrum of galaxies using published power spectra of galaxies and clusters of galaxies. On small scales we use the power spectrum derived from the 2-dimensional distribution of APM galaxies, on large scales we use power spectra derived from 3-dimensional data for galaxy and cluster samples. Spectra are reduced to real space and to the amplitude of the power spectrum of APM galaxies. Available data indicate the presence of two different populations in the nearby Universe. Clusters of galaxies sample a relatively large region in the Universe where rich, medium and poor superclusters are well represented. Their mean power spectrum has a spike on scale 120 h^{-1}Mpc, followed by an approximate power-law spectrum of index n = -1.9 towards small scales. The power spectrum found from LCRS and IRAS 1.2 Jy surveys is flatter around the maximum, which may represent regions of the Universe with medium-rich and poor superclusters.

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arXiv1998

Steps toward the power spectrum of matter. II. The biasing correction with sigma_8 normalization

A new method to determine the bias parameter of galaxies relative to matter is suggested. The method is based on the assumption that gravity is the dominating force which determines the formation of the structure in the Universe. Due to gravitational instability the galaxy formation is a threshold process: in low-density environments galaxies do not form and matter remains in primordial form. We investigate the influence of the presence of void and clustered populations to the power spectrum of matter and galaxies. The power spectrum of galaxies is similar to the power spectrum of matter; the fraction of total matter in the clustered population determines the difference between amplitudes of fluctuations of matter and galaxies, i.e. the bias factor. To determine the fraction of matter in voids and clustered population we perform numerical simulations. The fraction of matter in galaxies at the present epoch is found using a calibration through the sigma_8 parameter.

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arXiv1998

Steps toward the power spectrum of matter. III. The primordial spectrum

Observed power spectrum of matter found in Papers I and II is compared with analytical power spectra. Spatially flat cold and mixed dark matter models with cosmological constant and open models are considered. The primordial power spectrum of matter is determined using the power spectrum of matter and the transfer functions of analytical models. The primordial power spectrum has a break in amplitude. We conclude that a scale-free primordial power spectrum is excluded if presently available data on the distribution of clusters and galaxies represent the true mass distribution of the Universe.

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arXiv1998

The Power Spectrum of Matter

We calculate the mean power spectrum of galaxies using published power spectra of galaxies and clusters of galaxies. The mean power spectrum has a relatively sharp maximum on scale 120 Mpc (for Hubble constant h=1), followed by an almost exact power-law spectrum of index n = -1.9 toward smaller scales. The power spectrum found from APM 2-D galaxy distribution and from LCRS and IRAS 1.2 Jy surveys is flatter around the maximum. Power spectra of galaxies and matter are similar in shape, we find the bias parameter of galaxies relative to matter 1.3 + - 0.1. We compare the empirical power spectrum of matter with analytical power spectra and show that the primordial power spectrum has a break in amplitude and a spike.

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arXiv1998

Structure and Evolution of Stellar Populations in Local Group Galaxies

We use detailed modeling of stellar populations of nearby galaxies to calculate population parameters. Our sample of galaxies includes most galaxies of the Local Group and several more distant giant galaxies. Available data are sufficient to decompose galaxies into the nucleus, the metal rich core, the bulge, the halo, the young and old disks, and the dark halo. We compare mass-to-luminosity ratios and colors of bulges, disks and halos with results of models of galactic chemical evolution. The luminosity weighted mean of the mass-to-luminosity ratio of visible stellar population is M/L_B = 4 +- 1.4 in solar units. This ratio is surprisingly constant for galaxies of very different absolute magnitude.

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arXiv1998

The Supercluster-Void Network. IV. The Shape and Orientation of Superclusters

We present a study of the shape, size, and spatial orientation of superclusters of galaxies. Approximating superclusters by triaxial ellipsoids we show that superclusters are flattened, triaxial objects. We find that there are no spherical superclusters. The sizes of superclusters grow with their richness: the median semi-major axis of rich and poor superclusters (having at least 8 and less than 8 member clusters) is 42 and 31 Mpc, respectively. Similarly, the median semi-minor axis is 12 and 5 Mpc for rich and poor superclusters. The spatial orientation of superclusters, as determined from the axes of ellipsoids, is nearly random. We do not detect any preferable orientation of superclusters, neither with respect to the line of sight, nor relative to some other outstanding feature in the large scale structure, nor with respect to the directions of principal axes of adjacent superclusters.

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arXiv1997

A 120 Mpc scale in the Universe

Recent analysis of the distribution of clusters of galaxies is reviewed. Clusters of galaxies located in rich superclusters form a quasiregular lattice with a step size 120 Mpc. The power spectrum of clusters of galaxies has a sharp peak at the same wavelength. The matter power spectrum is compared with angular spectrum of background radiation for a wide variety of cosmological parameters. It is shown that the peaked spectrum is in agreement with CMB data. The peak in the power spectrum may be due to processes during the inflationary stage of the structure evolution.

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arXiv1997

Large scale structure of the Universe: Introduction

The changes of main paradigms on the structure and evolution of the Universe are reviewed. Two puzzles of the modern cosmology, the mean density of matter and the regularity of the Universe on large scales, as well as the possibility to solve these puzzles by the introduction of more complicated form of inflation, are discussed.

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arXiv1997

Has the Universe a honeycomb structure?

Recent analysis of the distribution of clusters of galaxies is reviewed. Clusters of galaxies located in rich superclusters form a quasiregular lattice similar in structure to honeycombs. The power spectrum of clusters of galaxies has a sharp peak at wavelength 120 Mpc corresponding to the lattice step. The peak in the spectrum may be due to processes during the inflationary stage of the structure evolution.

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arXiv1997

Regularity of the large-scale structure of the Universe

The distribution of Abell-ACO clusters of galaxies shows that clusters located in rich superclusters form a quasiregular network with step size 120 Mpc. The power spectrum of clusters of galaxies has a sharp peak at a wavelength equal to the step size of the network, the correlation function of clusters is oscillating with this period. We show that spectra with a spike are in agreement with temperature anisotropies measured by the Saskatoon experiment. The corresponding initial power spectrum of matter has a peak followed by a break.

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arXiv1997

Void Hierarchy in the Northern Local Void: Faint structures in low density regions of the nearby Universe

The Northern Local Void is a huge underdense region of the nearby Universe situated between the Hercules, Coma and Local Superclusters. We present an investigation of the galaxy distribution in the Northern Local Void using void statistics. In particular galaxies of different morphological type and luminosity have been studied separately and void catalogues have been compiled from three different luminosity limited galaxy samples for the first time. Our approach is complementary to most other methods usually used in Large-Scale Structure studies and has the potential to detect and describe subtle structures in the galaxy distribution. We found that the resulting sets of voids form a hierarchical system: The fainter the limiting luminosity of the galaxies the smaller are the voids defined by them. Voids outlined by bright galaxies are interlaced by a fine network of faint galaxy filaments dividing them into smaller subvoids. This Void Hierarchy is an important property of the Large-Scale Structure in the Universe which constrains any realistic galaxy and structure formation scenario. In addition, this concept of Void Hierarchy may help to devise new concepts for the study of the Large-Scale Structure in the Universe.

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arXiv1997

A built-in scale in the initial spectrum of density perturbations: evidence from cluster and CMB data

We calculate temperature anisotropies of the cosmic microwave background (CMB) for several initial power spectra of density perturbations with a built-in scale suggested by recent optical data on the spatial distribution of rich clusters of galaxies. Using cosmological models with different values of spectral index, baryon fraction, Hubble constant and cosmological constant, we compare the calculated radiation power spectrum with the CMB temperature anisotropies measured by the Saskatoon experiment. We show that spectra with a sharp peak at 120 h^{-1} Mpc are in agreement with the Saskatoon data. The combined evidence from cluster and CMB data favours the presence of a peak and a subsequent break in the initial matter power spectrum. Such feature is similar to the prediction of an inflationary model where an inflaton field is evolving through a kink in the potential.

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arXiv1997

The supercluster--void network II. An oscillating cluster correlation function

We use rich clusters of galaxies in the Northern and Southern Galactic hemispheres up to a redshift z=0.12 to determine the cluster correlation function. We show that superclusters of galaxies and voids between them form a moderately regular network. As a result the correlation function determined for clusters located in rich superclusters oscillates: it has a series of regularly spaced secondary maxima and minima. The scale of the supercluster-void network, determined from the period of oscillations, is P=115 Mpc. The amplitude of oscillations is about 3 times larger than the estimated error. We compare the observed cluster correlation function with similar functions derived for popular models of structure formation. We find that the production of the observed cluster correlation function in any model with a smooth transition of the power spectrum from a Harrison-Zeldovich regime with positive spectral index on long wavelengths to a negative spectral index on short wavelengths is highly unlikely. The power spectrum must have an extra peak located at the wavelength equal to the period of oscillations of the correlation function.

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arXiv1997

The supercluster--void network III. The correlation function as a geometrical statistic

We investigate properties of the correlation function of clusters of galaxies using geometrical models. On small scales the correlation function depends on the shape and the size of superclusters. On large scales it describes the geometry of the distribution of superclusters. If superclusters are distributed randomly then the correlation function on large scales is featureless. If superclusters and voids have a tendency to form a regular lattice then the correlation function on large scales has quasi-regularly spaced maxima and minima of decaying amplitude; i.e., it is oscillating. The period of oscillations is equal to the step size of the grid of the lattice. We calculate the power spectrum for our models and compare the geometrical information of the correlation function with other statistics. We find that geometric properties (the regularity of the distribution of clusters on large scales) are better quantified by the correlation function. We also analyse errors in the correlation function and the power spectrum by generating random realizations of models and finding the scatter of these realizations.

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arXiv1997

A 120-Mpc Periodicity in the Three-Dimensional Distribution of Galaxy Superclusters

Using a new compilation of available data on galaxy clusters and superclusters we present evidence for a quasiregular three-dimensional network of rich superclusters and voids, with the regions of high density separated by about 120 Mpc. We calculate the power spectrum for clusters of galaxies; it has a peak on the wavelength equal to the step of the network; the excess in the amplitude of the spectrum over that of the cold dark matter model is by a factor of 1.4. The probability that the spectrum can be formed within the framework of the standard cosmogony is very small. If the cluster distribution reflects the distribution of all matter (luminous and dark), then there must exists some hithero unknown process that produces regular structure on large scales.

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arXiv1996

The Las Campanas Redshift Survey Galaxy-Galaxy Autocorrelation Function

Presented are measurements of the observed redshift-space galaxy-galaxy autocorrelation function, xi(s), for the Las Campanas Redshift Survey (LCRS). For separations 2.0/h Mpc < s < 16.4/h Mpc, xi(s) can be approximated by a power law with slope of -1.52 +/- 0.03 and a correlation length of s_0 = (6.28 +\- 0.27)/h Mpc. A zero-crossing occurs on scales of roughly 30 - 40/h Mpc. On larger scales, xi(s) fluctuates closely about zero, indicating a high level of uniformity in the galaxy distribution on these scales. In addition, two aspects of the LCRS selection criteria - a variable field-to-field galaxy sampling rate and a 55 arcsec galaxy pair separation limit - are tested and found to have little impact on the measurement of xi(s). Finally, the LCRS xi(s) is compared with those from numerical simulations; it is concluded that, although the LCRS xi(s) does not discriminate sharply among modern cosmological models, redshift-space distortions in the LCRS xi(s) will likely provide a strong test of theory.

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arXiv1995

Evolution of the Supercluster-Void Network

Recently, the observed cellular nature of the large-scale structure of the Universe with its quasi-regular pattern of superclusters and voids has been pointed out by several authors. In this paper, we investigate properties of the initial power spectrum which lead to prediction of structure consistent with these observations.For this purpose, we analyze the evolution of structure within four sets of 2- and 3-dimensional cosmological models, which differ in their initial power spectrum. The models include HDM and CDM models as well as double power-law models. We discuss in detail the impact of model parameters such as the large scale and small scale power and the position and height of the maxima of the power spectra on the predicted structure. The best agreement with observations was observed in the model with the Harrison-Zeldovich spectrum on large scales, a power index $n\approx -1.5$ on small scales, and a maximum of the power spectrum at $\approx 130$~\Mpc. In this model the distribution of masses of clusters and superclusters, the correlation function of clusters, and the void distribution reproduce well the respective observed distributions. We also investigated the dynamical evolution of the supercluster-void structure. The results show that the basic supercluster-void network is formed very early and is essentially given by initial conditions.

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