M. Einasto, E. Saar, V. J. Martinez, J. Einasto, L. J. Liivam"agi, E. Tago, J. -L. Starck, V. Mueller, P. Hein"am"aki, P. Nurmi, S. Paredes, M. Gramann, G. Huetsi
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23 pages, accepted for publication in The Astrophysical Journal
We present a morphological study of the two richest superclusters from the 2dF Galaxy Redshift Survey (SCL126, the Sloan Great Wall, and SCL9, the Sculptor supercluster). We use Minkowski functionals, shapefinders, and galaxy group information to study the substructure of these superclusters as formed by different populations of galaxies. We compare the properties of grouped and isolated galaxies in the core region and in the outskirts of superclusters. The fourth Minkowski functional $V_3$ and the morphological signature $K_1$- $K_2$ show a crossover from low-density morphology (outskirts of supercluster) to high-density morphology (core of supercluster) at mass fraction $m_f \approx 0.7$. The galaxy content and the morphology of the galaxy populations in supercluster cores and outskirts is different. The core regions contain a larger fraction of early type, red galaxies, and richer groups than the outskirts of superclusters. In the core and outskirt regions the fine structure of the two prominent superclusters as delineated by galaxies from different populations also differs. Our results suggest that both local (group/cluster) and global (supercluster) environments are important in forming galaxy morphologies and colors (and determining the star formation activity). The differences between the superclusters indicate that these superclusters have different evolutional histories (Abridged).
We use catalogues of superclusters of galaxies from the 2dF Galaxy Redshift Survey to study the properties of galaxies in superclusters. We compare the properties of galaxies in high and low density regions of rich superclusters, in poor superclusters and in the field, as well as in groups, and of isolated galaxies in superclusters of various richness. We show that in rich superclusters the values of the luminosity density smoothed on a scale of 8 \Mpc are higher than in poor superclusters: the median density in rich superclusters is $δ\approx 7.5$, in poor superclusters $δ\approx 6.0$. Rich s…
We study the morphology of the richest superclusters from the catalogues of superclusters of galaxies in the 2dF Galaxy Redshift Survey and compare the morphology of real superclusters with model superclusters in the Millennium Simulation. We use Minkowski functionals and shapefinders to quantify the morphology of superclusters: their sizes, shapes, and clumpiness. We generate empirical models of simple geometry to understand which morphologies correspond to the supercluster shapefinders. We show that rich superclusters have elongated, filamentary shapes with high-density clumps in their core …
We investigate properties of superclusters of galaxies found on the basis of the 2dF Galaxy Redshift Survey, and compare them with properties of superclusters from the Millennium Simulation. We study the dependence of various characteristics of superclusters on their distance from the observer, on their total luminosity, and on their multiplicity. The multiplicity is defined by the number of Density Field (DF) clusters in superclusters. Using the multiplicity we divide superclusters into four richness classes: poor, medium, rich and extremely rich. We show that superclusters are asymmetrical a…
We study the morphology of galaxy populations of the richest superclusters from the catalogue of superclusters of galaxies in the 2dF Galaxy Redshift Survey using the luminosity density distribution and Minkowski functional V3. We compare the properties of grouped and isolated galaxies in regions of different density in superclusters. We find that in high-density cores of rich superclusters there is an excess of early type, passive galaxies, among galaxies in groups and clusters, as well as among those which do not belong to groups, while in lower density outer regions there are more blue, sta…
We study the spatial distribution of loose groups from the Las Campanas Redshift Survey, comparing it with the supercluster-void network delineated by rich clusters of galaxies. We use density fields and the friends-of-friends algorithm to identify the members of superclusters of Abell clusters among the Las Campanas loose groups. We find that systems of loose groups tend to be oriented perpendicularly to the line-of-sight, and discuss possible reasons for that. We show that loose groups in richer systems (superclusters of Abell clusters) are themselves also richer and more massive than groups…
We investigate the distribution of superclusters and voids using a new catalogue of superclusters of rich clusters of galaxies which extends up to a redshift of z=0.12. The new catalogue contains 220 superclusters of rich clusters, of which 90 superclusters have been determined for the first time. Two thirds of those superclusters with eight or more member clusters are concentrated to a Dominant Supercluster Plane almost perpendicular to the plane of the Local Supercluster. Several independent methods indicate consistently the presence of a quite regular supercluster-void network with scale of…
The Pisces-Cetus supercluster (redshift z~0.06) is one of the richest nearby (z<0.1) superclusters of galaxies, and emerges as a remarkable filament of galaxies at the edges of the two-degree-field galaxy redshift survey and the ongoing Sloan Digital Sky Survey. We explore the extent of the supercluster on the sky and in redshift space, and map the distribution of its constituent clusters and groups. We find evidence of enhanced star formation in galaxies belonging to groups in the supercluster compared to those in the field. This effect appears to be higher among the poorer groups than in the…
Rich clusters of galaxies are the most massive virialized systems known. Even though they contain only a small fraction of all galaxies, rich clusters provide a powerful tool for the study of galaxy formation, dark matter, large-scale structure, and cosmology. Superclusters, the largest known systems of galaxies, extend to (approx) 100h^{-1} Mpc in size and highlight the large-scale structure of the universe. This large-scale structure reflects initial conditions in the early universe and places strong contraints on models of galaxy formation and on cosmology. Some of the questions that can be…
We study the distribution of X-ray selected clusters of galaxies with respect to superclusters determined by Abell clusters of galaxies and show that the distribution of X-ray clusters follows the supercluster-void network determined by Abell clusters. We find that in this network X-ray clusters are more strongly clustered than other clusters. Poor, non-Abell X-ray clusters follow the supercluster-void network as well: these clusters are embedded in superclusters determined by rich clusters and populate filaments between them. We present a new catalog of superclusters of Abell clusters out to …
We use rich clusters of galaxies in the Northern and Southern Galactic hemispheres up to a redshift z=0.12 to determine the cluster correlation function. We show that superclusters of galaxies and voids between them form a moderately regular network. As a result the correlation function determined for clusters located in rich superclusters oscillates: it has a series of regularly spaced secondary maxima and minima. The scale of the supercluster-void network, determined from the period of oscillations, is P=115 Mpc. The amplitude of oscillations is about 3 times larger than the estimated error.…
We present new radial velocities for 306 bright (R<16) galaxies in a 77 square deg region of the Shapley supercluster measured with the FLAIR-II spectrograph on the UK Schmidt Telescope. The galaxies we measured were uniformly distributed over the survey area in contrast to previous samples which were concentrated in several rich Abell clusters. Most of the galaxies (230) were members of the Shapley supercluster: they trace out two previously unknown sheets of galaxies linking the Abell clusters of the supercluster. In a 44 square deg area of the supercluster excluding the Abell clusters, thes…
We generate the 2-dimensional high-resolution density field of galaxies of the Early Data Release of the Sloan Digital Sky Survey and the Las Campanas Redshift Survey with a smoothing length 0.8 Mpc/h to extract clusters and groups of galaxies, and a low-resolution field with a smoothing length 10 Mpc/h to extract superclusters of galaxies. We investigate properties of density field clusters and superclusters and compare the properties of these clusters and superclusters with those of Abell clusters, and superclusters found on the basis of Abell clusters. We found that clusters in a high-densi…
Two-dimensional high-resolution density field of galaxies of the Las Campanas Redshift Survey (LCRS) with a smoothing length 0.8 Mpc/h is used to extract clusters and groups of galaxies, and a low-resolution field with a smoothing length 10 Mpc/h to find superclusters of galaxies. Properties of these density field (DF) clusters and superclusters are studied and compared with the properties of Abell clusters and superclusters, and LCRS loose groups. We calculate the DF-cluster luminosity function, and show that most luminous clusters in high-density environments are about ten times brighter tha…
High sensitivity 21-cm HI line observations, with an rms noise level of \sim 0.5 mJy, were made of 35 spiral galaxies in the Coma Supercluster, using the refurbished Arecibo telescope, which resulted in the detection of 25 objects. These data, combined with the measurements available from the literature, provide the set of HI data for 94% of all late-type galaxies in the Coma Supercluster with an apparent photographic magnitude m_p <15.7 mag. We confirm that the typical scale of HI deficiency around the Coma cluster is 2 Mpc, i.e. one virial radius. Comparing the HI mass function (HIMF) of clu…
We find clusters and superclusters of galaxies using the Data Release 1 of the Sloan Digital Sky Survey. Density fields with smoothing lengthst of 10 and 0.8 Mpc/h are calculated. We found that galaxies and clusters in a high-density environment have luminosities that are five to ten times higher than in a low-density environment. Numerical simulations show that in underdense regions most particles form a rarefied population of pregalactic matter whereas in overdense regions most particles form a clustered population in rich clusters. Simulations show also that very massive superclusters are g…
The core region is dominated by three rich Abell clusters and two poor clusters. Their spatial distributions of gas temperature and metal abundance provide us with information on the interactions and motions of member clusters. From eight ASCA pointing observations, temperature, abundance, and X-ray luminosity for five member clusters are similar to the other field clusters not belonging to superclusters. This result and the mean gravitational mass density of the core region indicate that the members are growing in the same way as the nonmember clusters, and the core of the supercluster is jus…
Using a new compilation of available data on galaxy clusters and superclusters we present evidence for a quasiregular three-dimensional network of rich superclusters and voids, with the regions of high density separated by about 120 Mpc. We calculate the power spectrum for clusters of galaxies; it has a peak on the wavelength equal to the step of the network; the excess in the amplitude of the spectrum over that of the cold dark matter model is by a factor of 1.4. The probability that the spectrum can be formed within the framework of the standard cosmogony is very small. If the cluster distri…
This paper investigates the evolution of a void and an adjacent galaxy supercluster. For this purpose the quasispherical Szekeres model is employed. The Szekeres model is an exact solution of the Einstein field equations. In this way investigations of the evolution of the cosmic structures presented here can be freed from such assumptions as small amplitude of the density contrast. Studying the evolution of a void and an adjacent supercluster results not only in better understanding the evolution of cosmic structures but also in acquainting us with the Szekeres model. The main results include …
We have used the ROSAT All-Sky Survey to detect a known supercluster at z=0.087 in the North Ecliptic Pole region. The X-ray data greatly improve our understanding of this supercluster's characteristics, approximately doubling our knowledge of the structure's spatial extent and tripling the cluster/group membership compared to the optical discovery data. The supercluster is a rich structure consisting of at least 21 galaxy clusters and groups, 12 AGN, 61 IRAS galaxies, and various other objects. A majority of these components were discovered with the X-ray data, but the supercluster is also ro…
We study the distribution of galaxies and galaxy clusters in a 10^deg x 6^deg field in the Aquarius region. In addition to 63 clusters in the literature, we have found 39 new candidate clusters using a matched-filter technique and a counts-in-cells analysis. From redshift measurements of galaxies in the direction of these cluster candidates, we present new mean redshifts for 31 previously unobserved clusters, while improved mean redshifts are presented for 35 other systems. About 45% of the projected density enhancements are due to the superposition of clusters and/or groups of galaxies along …
We present the results of a redshift survey of both cluster and intercluster galaxies in the central part of the Shapley Concentration, the richest supercluster of clusters in the nearby Universe, consisting of ~2000 radial velocities. We estimate the total overdensity in galaxies of the supercluster and its mass and we discuss the cosmological implications of these results. Moreover, using a Principal Components Analysis technique, we study the influence of the cluster and supercluster dynamics on the galaxy spectral morphology.
We find clusters and superclusters of galaxies using the Data Release 1 of the Sloan Digital Sky Survey. We determine the luminosity function of clusters and find that clusters in a high-density environment have a luminosity a factor of ~5 higher than in a low-density environment. We also study clusters and superclusters in numerical simulations. Simulated clusters in a high-density environment are also more massive than those in a low-density environment. Comparison of the density distribution at various epochs in simulations shows that in large low-density regions (voids) dynamical evolution…
We study the infrared (K_s band) properties of clusters of galaxies in the Ursa Major supercluster using data from 2MASS (Two-Micron All-Sky Survey) and SDSS (Sloan Digital Sky Survey). We identified three large filaments with mean redshifts of z = 0.051, 0.060, and 0.071. All clusters of the supercluster are located in these filaments. We determined the total K_s-band luminosities and masses for 11 clusters of galaxies within comparable physical regions (within a radius R_200 close to the virial radius) using a homogeneous method. We constructed a combined luminosity function for the superclu…
We investigate the variation of current star formation in galaxies as a function of distance along three supercluster filaments, each joining pairs of rich clusters, in the Pisces-Cetus supercluster, which is part of the 2dFGRS. We find that even though there is a steady decline in the rate of star formation, as well as in the fraction of star forming galaxies, as one approaches the core of a cluster at an extremity of such a filament, there is an increased activity of star formation in a narrow distance range between 3-4/h_70 Mpc, which is 1.5-2 times the virial radius of the clusters involve…
We present the results from a multi-band optical imaging program which has definitively confirmed the existence of a supercluster at z = 0.91. Two massive clusters of galaxies, CL1604+4304 at z = 0.897 and CL1604+4321 at z = 0.924, were originally observed in the high-redshift cluster survey of Oke, Postman & Lubin (1998). They are separated by 4300 km/s in radial velocity and 17 arcminutes on the plane of the sky. Their physical and redshift proximity suggested a promising supercluster candidate. Deep BRi imaging of the region between the two clusters indicates a large population of red galax…
(abridged) We present the results of a redshift survey of intercluster galaxies in the central region of the Shapley Concentration supercluster, aimed at determining the distribution of galaxies in between obvious overdensities. Our sample is formed by 442 new redshifts, mainly in the b_J magnitude range 17-18.8. Adding the data from our redshift surveys on the A3558 and A3528 complexes, which are close to the geometrical centre of this supercluster, we obtain a total sample of ~2000 radial velocities. Using the 1440 galaxies of our total sample in the magnitude range 17 - 18.8, we reconstruct…
With the help of a statistical parameter derived from optical spectra, we show that the current star formation rate of a galaxy, falling into a cluster along a supercluster filament, is likely to undergo a sudden enhancement before the galaxy reaches the virial radius of the cluster. From a sample of 52 supercluster-scale filaments of galaxies joining a pair of rich clusters of galaxies within the two-degree Field Redshift Survey region, we find a significant enhancement of star formation, within a narrow range between 2-3 h/70 Mpc of the centre of the cluster into which the galaxy is falling.…
We investigate the distribution of clusters of galaxies and determine the cluster correlation function and power spectrum. Clusters of galaxies located in rich superclusters with at least 8 members form a quasiregular network of superclusters and voids. The correlation function of clusters in rich superclusters is oscillating with a period of 120 Mpc (for Hubble constant h=1), the power spectrum for the whole cluster sample has a peak at the corresponding wavelength. The power index on small wavelengths is n=-1.8, on large wavelengths the power index is within observational errors compatible w…
We present results of our wide-field redshift survey of galaxies in a 285 square degree region of the Shapley Supercluster (SSC), based on a set of 10529 velocity measurements (including 1201 new ones) on 8632 galaxies obtained from various telescopes and from the literature. Our data reveal that the main plane of the SSC (v~ 14500 km/s) extends further than previous estimates, filling the whole extent of our survey region of 12~degrees by 30~degrees on the sky (30 x 75~h-1 Mpc). There is also a connecting structure associated with the slightly nearer Abell~3571 cluster complex (v~ 12000km/s. …
3D Voronoi's tessellation method was first applied to identify groups of galaxies in the structure of a supercluster. The sample under consideration consists of more than 7000 galaxies of the Local Supercluster (LS) with radial velocities up to 3100 km/s. Because of an essential non-homogeneity of the LS catalogue, it was proposed to overscale distances in such an ''artificial'' way that the concentration of galaxies was varying as with increase of the distance a power-behaved function with the same exponent beta as for the full homogeneous catalogue. Various parameters of clustering were taki…
We present a weak shear analysis of the Abell 901/902 supercluster, composed of three rich clusters at z=0.16. Using a deep R-band image from the 0.5 x 0.5 degree MPG/ESO Wide Field Imager together with supplementary B-band observations, we build up a comprehensive picture of the light and mass distributions in this region. We find that, on average, the light from the early-type galaxies traces the dark matter fairly well, although one cluster is a notable exception to this rule. The clusters themselves exhibit a range of mass-to-light (M/L) ratios, X-ray properties, and galaxy populations. We…
We present new results of our wide-field redshift survey of galaxies in a 182 square degree region of the Shapley Supercluster (SSC) based on observations with the FLAIR-II spectrograph on the UK Schmidt Telescope. We present new measurements to give a total sample of redshifts for 710 bright (R<16.6) galaxies, of which 464 are members of the SSC (8000<v<18000 kms). Our data reveal that the main plane of the SSC extends further than previously realised, filling the whole extent of our survey region of 10 degrees by 20 degrees on the sky (35 Mpc by 70 Mpc). There is also a significant structure…
Using the apparatus of correlation Gamma-function (``conditional density''), we have analyzed spatial clustering of objects from several different samples of galaxies, clusters and superclusters. On small scales the distribution of objects obeys a power law drop of density with a power index of 0.9--1.5. On a scale of ~30 Mpc for independent samples of bright galaxies and clusters of galaxies we have detected a pronounced break in the slope of the Gamma-function with a power index decreasing to ~0.3. The clustering is much less pronounced in the region from 40 to 100 Mpc, and there is reason t…
We perform a weak lensing and photometric study of the z=0.42 supercluster MS0302+17 using deep I and V band images taken with the UH8K CCD mosaic camera at the CFHT. We use archival ROSAT HRI data to estimate fluxes, gas masses and, in one case, the binding mass of the three major clusters. We then use our CCD data to determine the optical richness and luminosities of the clusters and to map out the spatial distribution of the early type galaxies in the supercluster and in other foreground and background structures. We measure the gravitational shear from a sample of \simeq 30,000 faint backg…
The availability of the Hipparcos Catalogue triggered many kinematic and dynamical studies of the solar neighbourhood. Nevertheless, those studies generally lacked the third component of the space velocities, i.e., the radial velocities. This work presents the kinematic analysis of 5952 K and 739 M giants in the solar neighbourhood which includes for the first time radial velocity data from a large survey performed with the CORAVEL spectrovelocimeter. It also uses proper motions from the Tycho-2 catalogue, which are expected to be more accurate than the Hipparcos ones. The UV-plane constructed…
Recently, it was suggested that large concentrations or groups of quasars may trace sites of enhanced matter density at medium and high redshifts analogous to how galaxy clusters trace them in nearby space. We have checked existing quasar data for the presence of such groups. Large Quasar Groups (LQGs) were identified using a well-known cluster analysis technique. Our final list consists of 12 groups, including one reported previously. Most of the quasars in these groups come from deep homogeneous surveys. We have found that: (i) the probability that the detected groups are random is rather sm…
We study the relationship between the mid-IR (5-18 $μ$m) emission of late-type galaxies and various other star formation tracers in order to investigate the nature of the dust heating sources in this spectral domain. The analysis is carried out using a sample of 123 normal, late-type, nearby galaxies with available data at several frequencies. The mid-IR luminosity (normalized to the H-band luminosity) correlates better with the far-IR luminosity than with more direct tracers of the young stellar population such as the H$α$ and the UV luminosity. The comparison of resolved images reveals a rem…
We analyse the cluster color-magnitude relation (CMR) for early-type galaxies in two of the richer clusters in the z ~ 0.9 supercluster system to derive average ages and formation redshifts for the early-type galaxy population. Both clusters were observed with the Advanced Camera for Surveys aboard the {\it Hubble Space Telescope} through the F606W and F814W filters, which brackets the rest-frame 4000 Åbreak at the cluster redshifts of z\sim 0.9. We fit the zeropoint and slope of the red cluster sequence, and model the scatter about this relation to estimate average galaxy ages and formation r…
Modern redshift surveys such as the 2 degree field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS) reveal the fully 3 dimensional distribution of a million or so galaxies over a large cosmological volume. Visually galaxies appear to be distributed along sheet-like and/or filamentary superclusters. The CfA Great Wall, Southern Great Wall and the recently discovered SDSS Great Wall are very spectacular superclusters. Clearly theoretical predictions for galaxy clustering must be tested against these rich datasets. This can be achieved by means of the Minkowski Functionals …
We present a new model for the creation of cool cores in rich galaxy clusters within a LambdaCDM cosmological framework using the results from high spatial dynamic range, adaptive mesh hydro/N-body simulations. It is proposed that cores of cool gas first form in subclusters and these subclusters merge to create rich clusters with cool, central X-Ray excesses. The rich cool clusters do not possess ``cooling flows'' due to the presence of bulk velocities in the intracluster medium in excess of 1000 km/sec produced by on-going accretion of gas from supercluster filaments. This new model has sever…
The Jeans criterion for the minimum self-gravitational condensation scale is extended to include the possibility of condensation on non-acoustic density nuclei at Schwarz scales, where structure formation begins in the plasma epoch at proto-supercluster masses about 10,000 years after the Big Bang, decreasing to galaxy masses at 300,000 years. Then the plasma universe became relatively inviscid gas and condensed to 10^23-26 kg "primordial fog particle" (PFP) masses. Baryonic dark matter by this theory should be mostly non-aggregated PFPs that persist in galactic halos. Schild (1996) suggests f…
We report a catalog of 509 pairs identified among 10403 nearby galaxies with line-of-sight velocities V_LG < 3500 km/s.We selected binary systems in accordance with two criteria (bounding and temporal), which require the physical pair of galaxies to have negative total energy and its components to be located inside the zero-velocity surface. We assume that individual galaxy masses are proportional to their total K-band luminosities, M = L_K x 6M/L. The catalog gives the magnitudes and morphological types of galaxies and also the projected (orbital) masses and pair isolation indices. The compon…
We use large-scale cosmological simulations to estimate the mass-to-light ratio of galaxy systems as a function of scale, and compare the results with observations of galaxies, groups, clusters, and superclusters of galaxies. We find remarkably good agreement between observations and simulations. Specifically, we find that the simulated mass-to-light ratio increases with scale on small scales and flattens to a constant value on large scales, as suggested by observations. We find that while mass typically follows light on large scales, high overdensity regions --- such as rich clusters and supe…
We analyze the properties of a sample of galaxies identified in a 21-cm, HI-line survey of selected areas in the Perseus-Pisces supercluster and its foreground void. Twelve fields were observed in the supercluster, five of them (target fields) centered on optically bright galaxies, and the other seven (blank fields) selected to contain no bright galaxies. We detected nine previously uncataloged, gas-rich galaxies, six of them in the target fields. We also detected HI from seven previously cataloged galaxies in these fields. Observations in the void covered the same volume as the twelve supercl…
It appears that the dynamical status of clusters and groups of galaxies is related to the large-scale structure of the Universe. A few interesting trends have been established: (1) The Cluster Substructure - Alignment Connection, by which clusters show a strong correlation between their tendency to be aligned with their neighbors and their dynamical state (as indicated by the existence of significant substructres). (2) The Cluster Dynamics -Cluster Clustering Connection, by which dynamically young clusters are more clustered than the overall cluster population. (3) The Cluster- Supercluster Al…
We present an analysis of the effects of environment on the photometric properties of galaxies in the core of the Shapley Supercluster at z=0.05, one of the most massive structures in the local universe. The Shapley Optical Survey (SOS) comprises archive WFI optical imaging of a 2.0 deg^2 region containing the rich clusters A3556, A3558 and A3562 which demonstrate a highly complex dynamical situation including ongoing cluster mergers. The B-R/R colour-magnitude relation has an intrinsic dispersion of 0.045 mag and is 0.015\pm0.005 mag redder in the highest-density regions, indicative of the re…
The distributions of peculiar velocities of rich clusters and of groups of galaxies are investigated for different cosmological models and are compared with observations. Four cosmological models are studied: standard ($Ω=1$) CDM, low-density CDM, HDM ($Ω=1$), and PBI. We find that rich clusters of galaxies exhibit a Maxwellian distribution of peculiar velocities in all models, as expected from a Gaussian initial density fluctuation field. The cluster 3-D velocity distribution is generally similar in the models: it peaks at $v \sim 500$ km s$^{-1}$, and extends to high cluster velocities of $v…
We present the results of a study of the spectral properties of galaxies in the central part of the Shapley Concentration, covering an extremely wide range of densities, from the rich cluster cores to the underlying supercluster environment. Our sample is homogeneous, in a well defined magnitude range (17=<b_J=<18.8) and contains ~1300 spectra of galaxies at the same distance, covering an area of ~26 sq.deg. These characteristics allowed an accurate spectral classification, that we performed using a Principal Components Analysis technique. This spectral classification, together with the [OII] …
The distributions of peculiar velocities of rich clusters and of groups of galaxies are investigated for different cosmological models and are compared with observations. Four cosmological models are studied: standard ($Ω=1$) CDM, low-density ($Ω=0.3$) CDM, HDM ($Ω=1$), and PBI ($Ω=0.3$), all COBE normalized. We find that rich clusters of galaxies exhibit a Maxwellian distribution of peculiar velocities in all models,as expected from a Gaussian initial density field. The cluster 3-D velocity distribution typically peaks at $v \sim 600$ km s$^{-1}$, and extends to high cluster velocities of $v …
The study of shapes of the images of objects is an important issue not only because it reveals its dynamical state but also it helps to understand the object's evolutionary history. We discuss a new technique in cosmological image analysis which is based on a set of non-parametric shape descriptors known as the Minkowski Functionals (MFs). These functionals are extremely versatile and under some conditions give a complete description of the geometrical properties of objects. We believe that MFs could be a useful tool to extract information about the shapes of galaxies, clusters of galaxies and…
We report the first results of a spectroscopic survey of galaxies in the core of the Shapley Concentration, the richest nearby supercluster of clusters of galaxies. We have measured 311 new galaxy redshifts in an area of $\sim 4.5$ square degrees centered around the Abell cluster A3558. Considering also the data already available in the literature, the total number of galaxy redshifts in this area amounts to more than 500. On the basis of these data we estimate the mean velocities and the velocity dispersions of the Abell clusters A3556, A3558 and the poor cluster SC 1329 -314. Finally, from a…
We investigated the structures on scales beyond the typical clusters of galaxies. These structures are crucial to understand the cosmic gravitational clustering in the pre-virialized stage, or quasilinear règime. Based on the multi-resolution analysis of the discrete wavelet transformation, we got statistical available ensembles of $r_{cl}$-clusters, i.e. the structures on scale $r_{cl}$, in the range $1 \leq r_{cl} \leq 24 h^{-1}$ Mpc for both N-body simulation and the IRAS 1.2 Jy galaxy survey samples. If the mass-to-light ratio on scales larger than clusters asymptotically reaches a constan…
The Shapley Concentration is the richest supercluster of clusters in the nearby universe and its core is a remarkable complex formed by the ACO clusters A3558, A3562 and A3556, and by the two minor groups SC 1327-312 and SC 1329-314. This structure has been studied in various wavelength bands, revealing that it is probably dynamically very active. In this paper we present 174 new galaxy redshifts in this cluster complex, which are added to the sample of 540 already existing velocities. The large number of redshifts permits a more accurate and robust analysis of the dynamical parameters of the …
Deep imaging data from the Keck II telescope are employed to study the globular cluster (GC) populations in the cores of six rich Abell clusters. The sample includes A754, A1644, A2124, A2147, A2151, and A2152, and spans the redshift range z = 0.035-0.066. The clusters also range in morphology from spiral-rich, irregular systems to centrally concentrated cD clusters rich in early-type galaxies. Globular cluster specific frequencies S_N and luminosity function dispersions are measured for a total of 9 galaxies in six central fields. The measured values of S_N for the six brightest cluster galax…
