Yu. V. Baryshev

On the quiescence of the Hubble flow in the vicinity of the Local Group - A study using galaxies with distances from the Cepheid PL-relation

Cepheid distances of local galaxies (<7 Mpc) are used to study the very nearby velocity field, as pioneered by Sandage (Sandage 1986) who also pointed out its remarkable properties: linearity and quietness. The new data show that the velocity dispersion in the distance range as seen from the barycentre of the Local Group 1-8 Mpc is as low as 38 km/sec. The local rate of expansion coincides with the global Hubble constant. Down to 1.5 Mpc we cannot detect a deviation from the linear Hubble flow. This puts an upper limit for the mass of the Local Group, for a wide class of Friedman models, including those with the cosmological constant.

Facts and ideas in modern cosmology

Abstract A review of the principles of observational testing of cosmological theories is given with a special emphasis on the distinction between observational facts and theoretical hypotheses. A classification of modern cosmological theories and possible observational tests for these theories is presented. The main rival cosmological models are analyzed from the point of view of observational testing of their initial hypothesis. A comparison of modern observational data with theoretical predictions is presented. In particular we discuss in detail the validity of the two basic assumptions of modern cosmology that are the Cosmological Principle and the Expanding Space Paradigm. It is found that classical paradigms need to be reanalyzed and that it is necessary to develop crucial cosmological tests to discriminate alternative theories.

Large scale correlations in galaxy clustering from the two degree field galaxy redshift survey

We study galaxy correlations from samples extracted from the 2dFGRS final release. Statistical properties are characterized by studying the nearest neighbor probability density, the conditional density and the reduced two-point correlation function. The result is that the conditional density has a power-law behavior in redshift space described by an exponent y = 0.8 ± 0.2 in the interval from about 1 Mpc/h, the average distance between nearest galaxies, up to about 40 Mpc/h, corresponding to radius of the largest sphere contained in the samples. These results are consistent with other studies of the conditional density and are useful to clarify the subtle role of finite-size effects on the determination of the two-point correlation function in redshift and real space.

The method of a two-point conditional column density for estimating the fractal dimension of the distribution of galaxies

We suggest a new method for estimating the fractal dimension of the spatial distribution of galaxies: the method of selected cylinders. We show the capabilities of this method by constructing a two-point conditional column density for galaxies with known redshifts from the LEDA database. The fractal dimension of a sample of LEDA and EDR SDSS galaxies has been estimated to be 2.1±0.1 for cylinder lengths of 200 Mpc. A major advantage of the suggested method is that it allows scales comparable to the catalog depth to be analyzed for galaxy surveys in the form of conical sectors and small fields in the sky.

The non-uniform distribution of galaxies from data of the SDSS DR7 survey

We have analyzed the spatial distribution of galaxies from the latest release of the Sloan Digital Sky Survey of galactic redshifts (SDSS DR7), applying the complete correlation function (conditional density), two-point conditional density (cylinder), and radial density methods. Our analysis demonstrates that the conditional density has a power-law form for scales lengths 0.5–30 Mpc/h, with the power-law corresponding to the fractal dimension D = 2.2 ± 0.2; for scale lengths in excess of 30 Mpc/h, it enters an essentially flat regime, as is expected for a uniform distribution of galaxies. However, in the analysis applying the cylinder method, the power-law character with D = 2.0 ± 0.3 persists to scale lengths of 70 Mpc/h. The radial density method reveals inhomogeneities in the spatial distribution of galaxies on scales of 200 Mpc/h with a density contrast of two, confirming that translation invariance is violated in the distribution of galaxies to 300 Mpc/h, with the sampling depth of the SDSS galaxies being 600 Mpc/h.

On the fractal nature of the large-scale structure of the universe

Abstract The observational evidences of the fractality of the large-scale distribution of galaxies are reviewed. A perfect linearity of the redshift-distance relation deeply inside the inhomogeneity cell in the fractal structure are stressed upon being contradictory to the traditional interpretation of the Hubble law as a consequence of homogeneity. It is shown that this contradiction could be resolved with allowance for the effect of gravitational cosmological redshift within a fractal structure with the fractal dimension DF ≃ 2.

MICROWAVE BACKGROUND RADIATION AND COSMOLOGICAL LARGE NUMBERS

Abstract The possible interpretations of the cosmic microwave background radiation (CMBR) in different cosmological models are reviewed. It is shown that the wavelength of the maximum in microwave background spectrum is expressed as a geometrical mean of the Planck and Hubble length: λMB ∼. This is not a coincidence but a direct consequence of physical laws in an extreme selfgravitating object, “Hubbloid”, with an upper limit of equilibrium radiation temperature about 30 K.

Study of faint galaxies in the field of GRB021004

We present an analysis of BV RcIc observations of the field sized around 4′ × 4′ centered at the host galaxy of the gamma-ray burst GRB021004 with the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We measured the magnitudes and constructed the color diagrams for 311 galaxies detected in the field (S/N>3). The differential and integral counts of galaxies up to the limit, corresponding to 28.5 (B), 28.0 (V), 27.0 (Rc), 26.5 (Ic) were computed. We compiled the galaxy catalog, consisting of 183 objects, for which the photometric redshifts up to the limiting magnitudes 26.0 (B), 25.5 (V), 25.0 (Rc), 24.5 (Ic) were determined using the HyperZ code. We then examined the radial distribution of galaxies based on the z estimates. We have built the curves expected in the case of a uniform distribution of galaxies in space, and obtained the estimates for the size and contrast of the possible super-large-scale structures, which are accessible with the observations of this type.

Quasar-galaxy associations as lensing by middle-mass objects

Abstract We discuss the problem of associations between QSOs and galaxies. It is shown that under certain reliable assumptions some of the associations can be explained as gravitational lensing by middle-mass objects, which are situated in the haloes of giant galaxies, dwarf galaxies and globular clusters. The mass distribution of middle mass objects was approximated by the King profile. The large values of the bending angle near the lens core permit the dwarf galaxies and globular clusters to have good lensing properties (if their cores are transparent). The amplification in the central, image can reach 5–7m. We consider the catalogue of Arps pairs published by Burbidge G. et al, as a catalogue of quasars lensed by middle-mass objects in galactic surroundings. The distributions of redshifts of galaxies and quasars in this catalogue can help to obtain some knowledge on the number density of dwarf galaxies and globular clusters and their masses.

A new approach to the large cosmological numbers coincidences

Abstract A new line of interpretation of the Large Numbers coincidences based on the order of magnitude comparison of the Planck and Eddington luminosities is considered.