Piotr Flin

Substructures in Abell clusters of galaxies

Aims. We present the results of substructure detection on a large sample of Abell clusters. Methods. We apply the wavelet transform to positions of galaxies in 183 Abell clusters. The significance of the substructuring detected was determined using Monte Carlo simulations on sets of 1000 randomly generated distributions of galaxies for each cluster and wavelet scale. Results. 62 of the investigated clusters are strongly substructured; the frequency of occurrence of substructure is 0.34. The investigated clusters were classified as unimodal, bimodal or complex systems. The clusters were divided into clusters having substructures in the field of the cluster S f or in the core region S c . The Kolmogorov-Smirnov test show no significant differences at the level

Letter: Rotation of the Universe and the Angular Momenta of Celestial Bodies

\alpha=0.05

Some remarks on the angular momenta of galaxies, their clusters and superclusters

in the distribution of clusters having S c and S f substructures with redshift. Using a

THE ORIENTATIONS OF GALAXY GROUPS AND FORMATION OF THE LOCAL SUPERCLUSTER

\chi^2

ORIENTATION OF BRIGHTER GALAXIES IN NEARBY GALAXY CLUSTERS

test we found no correlation between the existence of subclustering and the morphological type of galaxy clusters.

Morphology and evolution of simulated and optical clusters: a comparative analysis

We discuss the equation of motion of the rotating homogenous and isotropic model of the Universe. We show that the model predicts the presence of a minimum in the relation between the mass of an astronomical object and its angular momentum. We show that this relation appears to be universal, and we predict the masses of structures with minimal angular momenta in agreement with observations. In such a manner we suggest the possibility at acquirement of angular momenta of celestial bodies during their formation from the global rotation of the Universe.

On the investigations of galaxy redshift periodicity

We discuss the relation between angular momenta and masses of galaxy structures base on the Li model of the universe with global rotation. In our previous paper [15] it was shown that the model predicts the presence of a minimum in this relation. In the present paper we discuss observational evidence allowing us to verify this relation. We find null angular momentum J = 0 for the masses corresponding to the groups mass of the galaxy, and non-vanishing angular momenta for other galactic structures. We check these theoretical predictions analysing Tully’s galaxy groups. The existing data comparing alignment in different galactic structures are consistent with the obtained theoretical relation J(M) if we interpret the growing alignment as the galactic increasing angular momenta in the galactic structure.

THE EVOLUTION OF LOW-REDSHIFT GALAXY STRUCTURES

We analyzed the orientation of galaxy groups in the Local Supercluster (LSC). It is strongly correlated with the distribution of neighboring groups in the scale up to about 20 Mpc. The group major axis is in alignment with both the line joining the two brightest galaxies and the direction toward the center of the LSC, i.e., Virgo cluster. These correlations suggest that two brightest galaxies were formed in filaments of matter directed toward the protosupercluster center. Afterward, the hierarchical clustering leads to aggregation of galaxies around these two galaxies. The groups are formed on the same or similarly oriented filaments. This picture is in agreement with the predictions of numerical simulations.

THE SHAPE OF GALAXY STRUCTURES

A sample of 6188 nearby galaxy structures, complete to rF = 183 and containing at least 10 members each, was the observational basis for an investigation of the alignment of bright galaxies with the major axes for the parent clusters. The distribution of position angles for galaxies within the clusters, specifically the brightest, the second brightest, the third, and the tenth brightest galaxies was tested for isotropy. Galaxy position angles appear to be distributed isotropically, as are the distributions of underlying cluster structure position angles. The characterization of galaxy structures according to richness class also appears to be isotropic. Characterization according to BM types, which are known for 1056 clusters, is more interesting. Only in the case of clusters of BM type I is there an alignment of the brightest cluster member with the major axis of the parent cluster. The effect is observed at the 2 significance level. In other investigated cases the distributions are isotropic. The results confirm the special role of cD galaxies in the origin/evolution of large-scale structures.

The environmental effects in the origin of angular momenta of galaxies

We have made a comparative study of morphological evolution in simulated dark matter (DM) haloes and X-ray brightness distribution, and in optical clusters. Samples of simulated clusters include star formation with supernovae feedback, radiative cooling and simulation in the adiabatic limit at three different redshifts, z= 0.0, 0.10 and 0.25. The optical sample contains 208 Abell, Corwin & Olowin (ACO) clusters within redshift, z≤ 0.25. Cluster morphology, within 0.5 and 1.0 h−1 Mpc from cluster centre, is quantified by multiplicity and ellipticity. We find that the distribution of the DM haloes in the adiabatic simulation appears to be more elongated than the galaxy clusters. Radiative cooling brings halo shapes in excellent agreement with observed clusters; however, cooling along with feedback mechanism makes the haloes more flattened. Our results indicate relatively stronger structural evolution and more clumpy distributions in observed clusters than in the structure of simulated clusters, and slower increase in simulated cluster shapes compared to those in the observed one. Within z≤ 0.1, we note an interesting agreement in the shapes of clusters obtained from the cooling simulations and observation. We also note that the different samples of observed clusters differ significantly in morphological evolution with redshift. We highlight a few possibilities responsible for the discrepancy in morphological evolution of simulated and observed clusters.