It has been a long-standing cosmological issue to explain why the statistical distribution of the radial pairwise peculiar velocity of galaxies has an exponential shape rather than the Gaussian, as suggested by observations and explicitly shown by results of N-body simulations. Previous explanations on the exponential distribution are based on highly nonlinear dynamics of galactic systems (R < 1h–1 Mpc). That is, the exponential feature appears as a result of superposition of Gaussian velocity distributions in clumps with various velocity dispersions. Hence although this model is suitable to account for a symmetric exponential distribution with vanishing mean net relative velocity, a more elaborate treatment is necessary in order to reproduce an asymmetric exponential distribution with its peak at a negative relative velocity as observed in numerical simulations.

By using the data of the CfA redshift catalogue(1995.4), the structure, substructures and some astrophysical properties of the Virgo galaxy cluster are studied in depth (Shao 1996).

We derive the gas mass function of clusters of galaxies to measure the density fluctuation spectrum on cluster scales. The baryon abundance confined in rich clusters is computed from the gas mass function and compared with the mean baryon density in the universe which is predicted by the BBN. This baryon fraction and the slope of the gas mass function put constraints on σ8 and the slope of the fluctuation spectrum. Adopting the density parameter of baryons Ωbh2 = 0.0175 ± 0.0075 and assuming that , we find for h = 0.7 ± 0.1. Our value of σ8 is independent of Ω0 and thus we can estimate Ω0 by combining σ8 as obtained in this study with those from Ω0-dependent analyses to date. Constraints are also derived for CDM and CHDM models.

Peebles (1997) has proposed a non-Gaussian χ2 isocurvature model which gives rise to early galaxy assembly at redshifts ≥ 3–4. We test whether the higher order moments (skewness and kurtosis) of such a model are compatible with the moments of the observed density field, and find that in the absence of bias these models produce moments that are much higher than those measured for the APM survey (Gaztañaga, 1994). We have applied different biasing schemes to see whether bias can bring the moments down, and find that for power law, Cen-Ostriker, and censor threshold biasing schemes (Mann et al 1997) the moments can be brought into agreement with the APM measurements only for linear bias values b > 3. This however, would give a redshift distortion parameter, βopticai = (Ω0.6/b) < 0.16 which is inconsistent with current estimates from redshift surveys of βoptical = 0.40 ± 0.12 (e.g. Peacock 1997). We conclude that for an acceptable level of bias in the schemes we have tested, the χ2 isocurvature model moments disagree with current measurements of skewness and kurtosis from the APM survey.

Anisotropies in luminosity distance-redshift relation (dL − z relation) caused by the large-scale structure (LSS) of the universe are studied. We solve the Raychaudhuri equation on FRW models taking account of LSS by the linear perturbation method. Numerical calculations to evaluate the amplitude of the anisotropies are done on flat models with cosmological constant and open models, employing Cold Dark Matter models and COBE-normalization for the power spectrum of the density perturbations.

We discuss the theoretical and observational implications of an inhomogeneous cosmological model consisting of three regions: the inner low-density homogeneous region, the self-similar (or partially similar) inhomogeneous region and the outer nearly flat homogeneous region. When we assume Einstein's gravitational theory without cosmological constant, the standard inflation theory, and the observational fact of local low density around us, this model is found to be reasonable. The boundary between the inner region and the self-similar region is assumed to be in a spherical shell corresponding to the epoch of redshift z = 1.5–2.0, when the numbers of QSOs and Ly α clouds changed rapidly.

Applying a discrete wavelet transformation (DWT)1 to the spiral (SP) and elliptical+lenticular (EL) galaxies in A PM bright galaxy catalog (APMBGC)2, we investigated the scale-dependence of bias parameter b in the linear bias model

We study the total luminosity function (LF) and the type-specific LF of 7 nearby clusters of galaxies (A1060, S805, A2063, A1736, A1644, A1631, and A754) using the R-band image (1.0 × 0.5 deg2) taken with our mosaic CCD camera mounted on 1-m telescope at the Las Campanas Observatory.

We carefully re-examine the evolution of small scale cosmological perturbations, motivated from the studies of cosmic structure formation in the high-z universe. Under the assumption of the hierarchical clustering scenario, the evolution of density fluctuations on very small scales is especially important for the early formation of the bound objects such as population III stars or primordial sub-galaxies.

We have investigated the scale-invariant solutions of the BBGKY equations for spatial correlation functions of cosmological density fluctuations and the mean relative peculiar velocity in the strongly nonlinear regime. It is found that the solutions for the mean relative physical velocity depend on the three-point spatial correlation function and the skewness of the velocity fields. We find that the stable condition in which the mean relative physical velocity vanishes on the virialized regions is satisfied only under the assumptions which Davis & Peebles took in there paper. It is found, however, that their assumptions may not be general in real. The power index of the two-point correlation function in the strongly nonlinear regime depends on the mean relative peculiar velocity, the three-point correlation function and the skewness. If self-similar solutions exist, then the power index in the strongly nonlinear regime is related to the power index of the initial power spectrum and its relation depends on the three-point correlation function and the skewness through the mean relative peculiar velocity. We also investigate stability of the solutions of the BBGKY equations for two-point spatial correlation functions. In the case that the background skewness is equal to 0, we found that there is no local instability in the strongly non-linear regime.

We investigate the cosmological model dependence of galaxy luminosity function (GLF) obtained by the Press–Schechter (PS) prescription. We consider the power–law spectra as well as a CDM spectrum for primordial density fluctuations, assuming a variety of cosmological models. We do not consider any galaxy luminosity (chemical) evolution in this report.

About 30000 sources were cataloged by the Miyun 232 MHz survey1 covering sky area north of declination 30°. (Zhang et al., 1997). For source count purpose, subcounts for different ratio of signal to noise and galactic latitude of steep-spectrum and flatspectrum sources were carried out respectively.

This review begins with a brief survey of the observational constraints on the standard big bang cosmology, pointing out that the various limits leave a very narrow window in the parameter space of plausible models. There is thus a strong case for alternative cosmologies. The rest of the review concentrates on one alternative, the quasi steady state cosmology (QSSC) and summarises the recent work on this model. This includes, the theoretical formulation and simple exact solutions of the basic equations, their relationship to observations, the stability of solutions and the toy model for understanding the growth of structures in the universe.

Modern cosmology began with the realization that there were solutions to Einstein's theory of gravity discovered by Friedmann and Lemaitre which when combined with the redshift distance relation of Hubble and others could be interpreted as showing that we live in an expanding universe. By 1930, the scientific establishment and many of the lay public believed this. It was then only elementary logic to argue that if time reversal was applied, the universe must originally have been so compact that we could talk of a beginning. Lemaitre tried to describe this state as the “Primeval Atom.” For a decade or so after the war, Gamow, Alpher and Herman and other leading physicists explored this dense configuration trying to make the chemical elements from protons and neutrons. They soon learned that this was not possible because of the absence of stable masses of five and eight, but they also realized that if such an early stage had occurred the universe would contain an expanding cloud of radiation which would preserve its black body form. Dicke and his colleagues in Princeton rediscovered this idea and decided to try and detect the radiation. Penzias and Wilson found such a radiation field, and COBE has demonstrated that it has a perfect black body form out to radio wavelengths. This history of the discovery together with the fact that the light elements D, He3 and He4 in about the right amounts can be made in a hot big bang has led to the widely held, but simplistic view, that the standard cosmology - the hot big bang - is correct.

Analysis of ROSAT observations demonstrate that X-ray sources are associated with bright Seyfert galaxies up to distances of about 40 arc min. These X-ray sources are predominantly identified with blue stellar objects (BSO's) some of which are already catalogued as quasars.

The X-ray sources tend to pair and align across the nucleus of the active Seyfert. Enough redshifts are now available to indicate the similarities of the redshifts in the quasar pairs and to enable computation of ejection velocities of about 0.1c.

Recently Arp (1997) has published a list of x-ray emitting blue stellar objects (BSO) around 24 Seyfert galaxies. Herewith we present our optical identification of 5 BSOs in the field NGC3516 obtained on April 4-5, 1997 using the 2.16m telescope at Xinlong Station, Beijing Astronomical Observatory. One of the objects Q1107+7232 with z=2.10 (θ = 4.34′, θ is the angular distance from the center of NGC3516) is already listed in the Hewitt-Burbidge Catalog (1993). We find the other four objects are all quasars: Q1108+7226 with z=0.328 (θ = 11.23′); Q1106+7244, z=0.690 (θ = 10.23′); Q1105+7242, z=0.930, (θ = 10.990; QH05+7238, z=1.399 (θ = 7.42′) Q1107+7232, z=2.10 (θ = 4.34′)

Large scale voids are a very prominent feature in recent redshift surveys: here we attempt an explanation in terms of a first order phase transition occurring during the slow roll epoch of a two field inflation, a process where one field drives the slow roll while the other undergoes quantum tunneling through a potential barrier. The ensuing bubble like perturbations – nucleated at a number of e-folds N ≈ 55 before reheating – are thought to be the precursors of the voids we observe today, while the zero-point fluctuations of the inflaton are the small, Gaussian perturbations seen by COBE on the large angular scales.

If this is so, primordial bubbles must have left a trace on the CMB, unless Silk damping and/or early reionization have erased it. We predict this imprint to have power on small angular scales, ≈ 10 arcmin or ≈ ≈ 1000. Therefore the physics at the Planck energy may be tested astronomically both indirectly through the large scale structure and directly through the forthcoming high resolution MAP and Planck satellites.

Evaluating the temperature fluctuation in the cosmic microwave background radiation, the viability of the one bubble inflation scenario is studied. It is shown that it is possible to construct a model which explains the creation of an open universe.

Mirror (shadow) particles are required to restore symmetry between left- and right-handed coordinate systems. If mirror world exists, it has been born at the same time as the ordinary world and has the same evolution (in the case of the shadow world - broken mirror symmetry, the evolution and structure of the shadow world does not correspond with the observed world). Mirror world is a kind of dark matter. According to Bahcall (1984) local dark matter has a density approximately equal to the density of observed (ordinary) matter.

A solution of the cosomlogical constant problem seems to come from a version of the scalar-tensor theory of gravity, which is characterized by a “nonminimal coupling“ in place of the standard Einstein-Hilbert action, where ɸ is the scalar field while ξ a constant. One then encounters an inherent question never fully answered: How can one single out a right conformai frame?