Redshift quantization - a review

Redshift quantization has three main facets: 1) the internal organization of galaxies, 2) differential effects between galaxies in physical systems, 3) global effects linking all galaxies and cosmology. The subject originated as an outgrowth of redshift correlation studies including studies of internal kinematics of galaxies. While possibly central to understanding redshift quantization, this aspect is complex and largely undeveloped. The bulk of the evidence for redshift quantization comes from differential and global periodicity testing. More recently redshift variability has been associated with the phenomenon. Early work in theory led to a determination ofq0 close to 0.5. A new association between quantization and the Cosmic Background Radiation further links redshift quantization with basic cosmology.     

Colour indices of the Markarian galaxies

By use of the ANS ultraviolet fluxes, optical (UBV) and IRAS infrared fluxes, several colour indices for a few Markarian galaxies have been investigated. A comparison of these indices with those for normal NGC galaxies has been carried out. Similarities and differences in the indices for the two groups of galaxies have been discussed and possible causes have been indicated.     

Galaxy photometry in the Virgo cluster. II

For two fields of the Virgo cluster of galaxies a photometry in B, V, and R has been performed. A total of 72 galaxies has been identified and their magnitudes and diameters have been determined.     

Quasi-periodical structures in the galaxy populations: mass and luminosity functions for the cluster galaxies

A search and estimation of the statistical significance of the quasi-periodical structures (QPS) has been carried out: for the luminosity function of the galaxies in a few rich clusters; for the integrated mass function of galaxies in the superclusters identified via = 21 cm observations. Some statistically significant QPS have been revealed. The periods for these structures are in agreement between each other, at this basis the hypothesis has been proposed that an effect of the QPS at the level of galaxies has some universal character. Frequency doubling has been discovered for these QPS.     

Concerning the errors arising through the use of Tully-Fisher relation for estimation of the Virgo cluster distance

The distance modulus of the Virgo cluster has been reexamined based on the Tully-Fisher relation between fully corrected B. ₁ ⁰ values and 21 cm velocity width derived from RC3 catalogue for spiral galaxies of Sbc-Sdm types, belonging to the “low-velocity” Virgo subcluster, singled out according to the statistical method proposed by Anosova, and led to the value μ = 31.15 ± 0.57 mag. A strong dependence of the intrinsic scatter in the Tully-Fisher relation on the apparent axes ratio of galaxies has been found, with a value of 0.4 mag for strongly flattened, highly inclined galaxies and galaxies with small inclinations and a value of 0.72 mag for objects with intermediate values of axes ratio. The restriction to samples only with galaxies with photoelectric observations does not lead to a considerable change of amplitude of scatter and decreases the value the of distance modulus. Published in Astrofizika, Vol. 42, No. 1, pp. 37–46, January–March, 1999.     

The role of diffuse matter in galactic coronas

An upper limit to the gas content in the coronas of giant galaxiesM _gas<0.04M _cor has been calculated on the basis of observational data on the emission of clusters of galaxies in different wavelength ranges. An analysis of companion galaxies has revealed a correlation of their morphological types with the distances to central giant galaxies. A gasodynamical interpretation of this regularity is suggested and a possible picture of the evolution of the galactic coronas is presented.     

The anisotropy of galaxy orientation in the Coma/A1367 supercluster

The spatial orientations of the galactic planes for galaxies in the Coma/A1367 supercluster have been determined. Owing to the ambiguity in the determination of the inclination angle, two possible orientations of the normal to the galaxy plane were found. Two angles, the polar angle δ _D and the azimuthal angle η , describe the orientation of normals. The distribution of both angles has been checked for isotropy. It is shown that the distribution is not isotropic. The same alignment is observed for samples containing elliptical and lenticular galaxies and for samples containing only spirals, as well as for samples containing galaxies located in different parts of the supercluster. In the case of spiral galaxies, the anisotropy shows that galaxy rotation axes strongly favour alignment with the main plane of the supercluster. The projection of the rotation axes on to the main plane of the supercluster has a preferential direction pointing towards the supercluster, but this effect is weak. A comparison with theory is also presented.     

Active Galactic Nuclei

The term Active Galactic Nuclei includes QSOs (Quasi-Stellar Objects), Seyfert galaxies, BL Lac objects and nuclei showing unusual amounts of star formation. South African work has centred on the photometric properties of these objects, both in the optical(UBVRI) and the infrared(JHKL). Photometry has been used to investigate the nature of the relevant emission mechanisms by studying both the colours of the nuclear components and their variations. In particular, it has been demonstrated convincingly that circumnuclear dust shells are present in several Seyfert 1 galaxies at temperatures of around 1500 K.It has also been shown that the variable component in many Seyfert 1 galaxies retains a constant spectral shape independent of its actual flux at a given time. Further, there is evidence that this shape is largely the same in all Seyfert 1 galaxies. Other studies have concentrated on surveys of morphological, spectroscopic and photometric characteristics of certain classes of galaxies such as those found by the IRAS satellite and those listed in the Arp-Madore catalogue of interacting galaxies.     

Some statistical properties of spiral galaxies along the Hubble sequence

A statistical study has been made for the variations along the Hubble sequence, os such parameters as the degree of tightness of winding of spiral arm λ, the pitch angle μ, the flatness of the disk H/D₂₅ and the thickness H along the Hubble sequence for 365 spiral galaxies published in A&Ap Supplement Series. The mean values of these quantities for the various Hubble types have been obtained for the first time. The results of the statistics show clearly 1) that the Hubble classification of spiral galaxies is one which has only a qualitative and statistical significance, and 2) that the dispersion relation in the density wave theory is valid for most spiral galaxies, i.e., the arms of most spiral galaxies satisfy the requirements of being tightly wound.     

Oxygen abundance in giant H II galaxies

A sample of 93 emission-line high luminosity galaxies from the Sloan Digital Sky Survey (SDSS) has been investigated. Line intensities have been measured in 116 SDSS spectra. Oxygen abundance has been determined in the studied galaxies. Since the auroral line of twice ionized oxygen [O III] λ 436.3 nm cannot be detected in the spectra of the sample, the intensity ratio of nebular to auroral lines needed to determine the electron temperature is calculated using the ff-relation. The oxygen abundances obtained in SDSS high luminosity galaxies are 0.2–0.5 dex lower than the maximum attainable value. This is caused by the fact that the sample includes only the gas-rich galaxies in which intense bursts of star formation occur. The equivalent number of O7 V stars which are responsible for excitation of luminescent H II regions in the studied sample is two or three orders of magnitude more than the number of stars which cause the luminescence of the brightest H II regions in nearby galaxies, and it exceeds by one order of magnitude the number of stars which cause gas in SBS 0335-052 E to glow.     

Spectrophotometric Study of Galaxies with UV Excess

Results from a spectrophotometric study of 21 galaxies with UV excess are presented. The half widths (FWHM) and equivalent widths of observed spectrum lines of these galaxies, as well as the relative intensities of the emission lines observed in the spectrum of the galaxy Kaz243, are determined. It is conjectured that the latter galaxy has the properties of an Sy2 type galaxy. The electron densities and masses of the gaseous components are found for 15 galaxies, along with the masses of 8 galaxies for which the ratio M/L has been calculated. It is shown that the spectral structures of these galaxies do not depend on whether they are members of physical systems or are isolated.     

Spectroscopy and photometry of ShCG 191 – Abell 1097

In the course of investigation of Shakhbazian compact groups we studied the group ShCG 191 which has been identified also as the Abell cluster A1097. By its richness it may be classified as a rich compact group or a poor cluster. We determined redshifts of 14 objects in the area of the cluster and found that two of the supposed members of the group are stars. Redshifts of 12 galaxies show that the system is gravitationally bound. The V and R magnitudes of 23 member galaxies and their morphological types are determined. We present in this paper also the surface brightness contours of member galaxies in the central area of the cluster, the curves of isophotal twisting and the Fourier parameter a₄. It is shown that some galaxies in the cluster are interacting with each other. Physical parameters of the group are close to those of ShCGs. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The close approaches and coalescence in triple systems of gravitating masses,I

By computer simulations, the dynamical evolution of plane triple systems of gaseous protogalaxies and galaxies with zero initial velocities has been studied. Inside the regionD of initial configurations some subregions have been revealed corresponding to a coalescence of protogalaxies on the first double approach. The average spin momenta of mergers are approximately equal to those typical of disk galaxies. In triple galaxies, a coalescence on the first double approach does not occur. The presence of significant hidden mass makes the approaches wider and prevents the coalescence of bodies in the systems without a central object. A central pair in a group of galaxies aids to coalescence. Also the change during time of the virial coefficient has been investigated.     

Structures in the large-scale distribution of galaxies with different luminosities

The large-scale structures of volume-limites subsample sorted out from the CfA catalog have been analysed by percolation method. The result shows that the features in the distribution of galaxies with different luminosities are significantly different. Especially, the most luminous galaxies are likely to exhibit hierarchical clustering on a scale about 50h ₅₀ ^–1 Mpc, and the least luminous galaxies in our subsamples show string-like or sheet-like character in their distribution. These results suggest that the large-scale distribution of galaxies consists of clusters or cluster cores of most luminous galaxies and the less luminous galaxies spread out from these cores with a string-like or sheet-like structure. This picture of the large-scale distribution consists with previous results from two-point correlation analysis and fractal analysis. The implication of these results has been discussed.     

Photometry of Chain-Like Groups of Compact Galaxies

The integrated V and R stellar magnitudes of 231 objects, comprising 42 chain-like groups of compact galaxies, have been measured. It has been determined, using a compactness parameter, that 92 of these objects are, with a high probability, stars. Of the 42 groups, 23 consist of galaxies in the vast majority.     

Search for nearby host galaxies of short gamma-ray bursts detected and well localized by BATSE/IPN

We have collected the observational data accumulated before the Swift experiment to check the possible connection of short gamma-ray bursts (GRBs) with low-redshift galaxies. The BATSE/IPN experimental data on well-localized short GRBs and the SDSS DR5 and PSCz catalogs of galaxies are used. The PSCz sky coverage has allowed us to search for host galaxies for a sample of 34 short GRBs. One or more galaxies have been found in the error boxes of six bursts, but the probability of a chance coincidence for each of them is high. No excess of nearby galaxies in the total sample has been detected. The 90% confidence limit corresponds to the fact that no more than 7%of the short GRBs could originate in nearby galaxies of the PSCz sample. The estimated upper limit of several percent may be considered to be valid in the volume z = 0.015–0.025. Based on the results of our search, we have estimated the lower limits for the isotropic energies E _γiso of 31 short bursts from our sample. Their values lie within the range 1.0 × 10⁴⁷–2.7 × 10⁴⁹ erg. The possible fraction of the flares from magnetars in our sample of short GRBs is discussed. The SDSS sky coverage is currently insufficient to perform a similar analysis.     

Modelling of seeing effects in extragalactic astronomy and cosmology

Convolution methods for modelling of astronomical seeing effects have been investigated. The advantages and disadvantages of several techniques are discussed, and particular attention is given to the fast Fourier transform (FFT) method. This method is then applied to two classes of problems, the structure of cores of elliptical galaxies, appearance of distant galaxies and the consequences of seeing effects in some cosmological tests. Estimates are presented for dimming of the central surface brightness and changes in the apparent core radius for elliptical galaxies, as well as seeing-induced changes in ellipticity. Modelling of galaxies with stellar nuclei has also been performed. Some consequences of these effects in investigations of dynamics of elliptical galaxies are addressed briefly. The influence of seeing in observational cosmology is discussed in the context of Hubble diagram (m-z) tests. It is shown that inadequate compensation for seeing effects can seriously distort the conclusions in such tests. Some suggestions for future work in this direction are offered.     

HCGs: stable and rotating systems?

It is shown that the radial velocity dispersion of the elongated HCGs (b/a ≤ 0.2) with smaller two‐dimensional galaxy‐galaxy median projected separation R is, on average, higher than those of the groups with larger R. It shows that galaxies in a group move preferentially along its elongation. Inspection of radial velocities of member galaxies in chain‐like and in roundish HCGs shows that galaxies in HCGs most probably rotate around the gravitational center of the corresponding group. Other two possible mechanisms: flying apart of galaxies from the group in opposite directions, and infall of field galaxies upon the group are excluded. It follows that HCGs are, probably, more stable formations, than it has been assumed. In this case the known inconsistencies between the results of the N‐body simulations and the observational facts are being excluded.     

Multiwavelength study of 230 IRAS FSC galaxies

A sample of 230 galaxies has been compiled based on their IRAS FSC fluxes to study their multiwavelength properties and carry out comparative analyses with other similar samples. To understand the nature of these galaxies, a comparison with a sample of bright ULIRGs having fluxes at 60 μm fν > 1 Jy and 14 optically faint IRAS FSC galaxies is presented. This comparison shows that galaxies found by IRAS are not always strong infrared sources and that the objects from the sample of ULIRGs represent a sample of extreme galaxies, which are very powerful infrared sources. We have confirmed the consistency between Star Formation Rates (SFRs) calibrated based on luminosities of the PAH feature at 7.7 μm and radio 1.4 GHz flux densities. We have estimated the extinction for our 230 objects using SFRs calibrated from the PAH feature compared to ultraviolet flux, which shows that only 1% of the ultraviolet continuum typically escapes extinction by dust within a starburst.     

Orientation of first-ranked galaxies in rich clusters

We present new evidence that first ranked galaxies are aligned with their parent cluster and with the direction of the nearest neighbour cluster (scale 15h ^–1 Mpc). The effect is stronger for cD and gE galaxies than for first-ranked galaxies of later type. The relevance of this result for different galaxy formation scenarios is discussed. In hierarchical clustering scenarios like the cold dark matter theory, galactic halos and clusters of galaxies are expected to have moderate asphericity. We present some numerical results of an on-going study of the dissipationless collapse of moderately aspherical systems. Our results indicate that the central part of the collapsed and virialized system does show the large scale elongation imposed by the initial conditions. It is pointed out that this may have important implications also for the properties of disk galaxies in dark halos.