Sloan Great Wall as a complex of superclusters with collapsing cores

Context. The formation and evolution of the cosmic web is governed by the gravitational attraction of dark matter and antigravity of dark energy (cosmological constant). In the cosmic web, galaxy superclusters or their high-density cores are the largest objects that may collapse at present or during the future evolution.Aims. We study the dynamical state and possible future evolution of galaxy superclusters from the Sloan Great Wall (SGW), the richest galaxy system in the nearby Universe.Methods. We calculated supercluster masses using dynamical masses of galaxy groups and stellar masses of galaxies. We employed normal mixture modelling to study the structure of rich SGW superclusters and search for components (cores) in superclusters. We analysed the radial mass distribution in the high-density cores of superclusters centred approximately at rich clusters and used the spherical collapse model to study their dynamical state.Results. The lower limit of the total mass of the SGW is approximately M = 2.5 x 10(16) h(-1) M-circle dot. Different mass estimators of superclusters agree well, the main uncertainties in masses of superclusters come from missing groups and clusters. We detected three high-density cores in the richest SGW supercluster (SCl 027) and two in the second richest supercluster (SCl 019). They have masses of 1.2-5.9 x 10(15) h(-1) M-circle dot and sizes of up to approximate to 60 h(-1) Mpc. The high-density cores of superclusters are very elongated, flattened perpendicularly to the line of sight. The comparison of the radial mass distribution in the high-density cores with the predictions of spherical collapse model suggests that their central regions with radii smaller than 8 h(-1) Mpc and masses of up to M = 2 x 10(15) h(-1) M-circle dot may be collapsing.Conclusions. The rich SGW superclusters with their high-density cores represent dynamically evolving environments for studies of the properties of galaxies and galaxy systems

Shell-like structures in our cosmic neighbourhood

Context. Signatures of the processes in the early Universe are imprinted in the cosmic web. Some of them may define shell-like structures characterised by typical scales. Examples of such structures are shell-like systems of galaxies, which are interpreted as a signatures of the baryon acoustic oscillations.Aims. We search for shell-like structures in the distribution of nearby rich clusters of galaxies drawn from the SDSS DR8.Methods. We calculated the distance distributions between rich clusters of galaxies and groups and clusters of various richness, searched for the maxima in the distance distributions and selected candidates of shell-like structures. We analysed the space distribution of groups and clusters that form shell walls.Results. We find six possible candidates of shell-like structures, in which galaxy clusters have the maximum in their distance distribution to other galaxy groups and clusters at a distance of about 120-130 h(-1) Mpc. Another, less probable maximum is found at a distance of about 240 h(-1) Mpc. The rich galaxy cluster A1795, which is the central cluster of the Bootes supercluster, has the highest maximum in the distance distribution of all other surrounding groups and clusters in our rich cluster sample. It lies at a distance of about 120 h(-1) Mpc. The structures of galaxy systems that cause this maximum form an almost complete shell of galaxy groups, clusters, and superclusters. The richest systems in the nearby universe, the Sloan Great Wall, the Corona Borealis supercluster, and the UrsaMajor supercluster, are among them. The probability that we obtain maxima like this from random distributions is lower than 0.001.Conclusions. Our results confirm that shell-like structures can be found in the distribution of nearby galaxies and their systems. The radii of the possible shells are larger than expected for a baryonic acoustic oscillations (BAO) shell (approximate to 109 h(-1) Mpc versus approximate to 120-130 h(-1) Mpc), and they are determined by very rich galaxy clusters and superclusters. In contrast, BAO shells are barely seen in the galaxy distribution. We discuss possible consequences of these differences

BOSS Great Wall: morphology, luminosity, and mass

Context. Galaxy superclusters are the largest systems in the Universe that can give us information about the formation and evolution of the cosmic web.Aims. We study the morphology of the superclusters from the BOSS Great Wall (BGW), a recently discovered very rich supercluster complex at the redshift z = 0.47.Methods. We have employed the Minkowski functionals to quantify supercluster morphology. We calculate supercluster luminosities and masses using two methods. Firstly, we used data about the luminosities and stellar masses of high stellar mass galaxies with log(M-*/h(-1) M-circle dot) >= 11.3. Secondly, we applied a scaling relation that combines morphological and physical parameters of superclusters to obtain supercluster luminosities, and obtained supercluster masses using the mass-to-light ratios found for local rich superclusters.Results. The BGW superclusters are very elongated systems, with shape parameter values of less than 0.2. This value is lower than that found for the most elongated local superclusters. The values of the fourth Minkowski functional V-3 for the richer BGW superclusters (V-3 = 7 and 10) show that they have a complicated and rich inner structure. We identify two Planck SZ clusters in the BGW superclusters, one in the richest BGW supercluster, and another in one of the poor BGW superclusters. The luminosities of the BGW superclusters are in the range of 1-8x10(13) h(2) L-circle dot, and masses in the range of 0.4-2.1x10(16) h(1) M-circle dot. Supercluster luminosities and masses obtained with two methods agree well.Conclusions. The BGW is a complex of massive, luminous and large superclusters with very elongated shape. The search and detailed study, including the morphology analysis of the richest superclusters and their complexes from observations and simulations can help us to understand formation and evolution of the cosmic web

The Sloan Great Wall. Rich clusters

We present the results of the study of the substructure and galaxy content of ten rich clusters of galaxies in three different superclusters of the Sloan Great Wall. We determine the substructure in clusters using the 'Mclust' package from the 'R' statistical environment and analyse their galaxy content. We analyse the distribution of the peculiar velocities of galaxies in clusters and calculate the peculiar velocity of the first ranked galaxy. We show that clusters in our sample have more than one component; in some clusters different components also have different galaxy content. We find that in some clusters with substructure the peculiar velocities of the first ranked galaxies are large. All clusters in our sample host luminous red galaxies. They can be found both in the central areas of clusters as well as in the outskirts, some of them have large peculiar velocities. About 1/3 of red galaxies in clusters are spirals. The scatter of colours of red ellipticals is in most clusters larger than that of red spirals. The presence of substructure in rich clusters, signs of possible mergers and infall, as well as the large peculiar velocities of the first ranked galaxies suggest that the clusters in our sample are not yet virialized. We present merger trees of dark matter haloes in an N-body simulation to demonstrate the formation of present-day dark matter haloes via multiple mergers during their evolution. In simulated dark matter haloes we find a substructure similar to that in observed clusters