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We have compiled a new sample of galaxies with published catalogs of HII region coordinates. This sample, together with the former catalog of Garcia-Gomez and Athanassoula (1991) will form the basis for subsequent studies of the spiral…
We compute the evolution of the space-dependent mass distribution of galaxies in clusters due to binary aggregations by solving a space-dependent Smoluchowski equation. We derive the distribution of intergalactic distance for different…
Using a multi-plane lensing method that we have developed, we follow the evolution of light beams as they propagate through inhomogeneous universes. We use a P3M code to simulate the formation and evolution of large-scale structure. The…
Any viable cosmological framework has to match the observed proportion of early- and late-type galaxies. In this contribution, we focus on the distribution of galaxy morphological types in the standard model of cosmology (Lambda cold dark…
We suggest a new scenario in which the Universe starts its evolution with a fractal topological structure. This structure is described by a gas of wormholes. It is shown that the polarization of such a gas in external fields possesses a…
The assumption that the universe is homogeneous and isotropic on large scales is one of the fundamental postulates of cosmology. We have tested the large scale homogeneity of the galaxy distribution in the Sloan Digital Sky Survey Data…
In order to understand nature of building blocks of galaxies in the early universe, we investigate "genuine irregular galaxies (GIGs)" in the nearby universe. Here, GIGs are defined as isolated galaxies without regular structures (spheroid,…
The empirical correlation between the H$\beta$ luminosity ($L$) and the ionized gas velocity dispersion ($\sigma$) in HII starburst galaxies (HIIGs) provides a foundation for using them as cosmological standard candles. A key unresolved…
We present a new approach to calculating the statistical distributions for magnification, shear, and rotation of images of cosmological sources due to gravitational lensing. In this approach one specifies an underlying Robertson-Walker…
The distribution of galaxies on the mass-size plane as a function of redshift or environment is a powerful test for galaxy formation models. Here we use integral-field stellar kinematics to interpret the variation of the mass-size…
The redshifts of lens galaxies in known gravitational lens systems probe the volume distribution of lensing mass. Following earlier work by Kochanek, we re-derive the lens redshift probability distribution, allowing for mass and number…
The properties of spatial distribution of luminous matter are investigated analysing all the available three dimensional catalogues of galaxies. In standard view, galaxies are believed to have a fractal distribution at small scale with a…
An overview over the current status of modeling galaxies by means of numerical simulations is given. After a short description of how galaxies form in hierarchically clustering scenarios, success and failures of current simulations are…
The distribution on the sky of unidentified sources at the highest energies where such a population is evident is investigated. For this purpose, sources without identification in the first Fermi-LAT catalog >10 GeV (1FHL) that are good…
Adopting known data on positions and distances, we make use of the analytical geometry and look for the plane that minimizes the distances of all galaxies to it. A planar distribution is indeed found that, however, does not coincide with…
The normalized inclination distributions are presented for the spiral galaxies in RC3. The results show that, except for the bin of $81^{\circ}$-$90^{\circ}$, in which the apparent minor isophotal diameters that are used to obtain the…
We use topological summaries based on Betti curves to characterize the large-scale spatial distribution of simulated dark matter haloes and galaxies. Using the IllustrisTNG and CAMELS-SAM simulations, we show that the topology of the galaxy…
We present the Morphology-Density and Morphology-Radius relations (T-Sigma and T-R, respectively) obtained from the WINGS database of galaxies in nearby clusters. Aiming to achieve the best statistics, we exploit the whole sample of…
Galaxy morphologies, kinematics, and stellar populations are thought to be linked to each other. However, both simulations and observations have pointed out mismatches therein. In this work, we study the nature and origin of the present-day…
We develop a new method which measures the projected density distribution w_p(r_p)n of photometric galaxies surrounding a set of spectroscopically-identified galaxies, and simultaneously the projected correlation function w_p(r_p) between…