3 research outputs found
Unusual A2142 supercluster with a collapsing core: distribution of light and mass
We study the distribution, masses, and dynamical properties of galaxy groups
in the A2142 supercluster. We analyse the global luminosity density
distribution in the supercluster and divide the supercluster into the
high-density core and the low-density outskirts regions. We find galaxy groups
and filaments in the regions of different global density, calculate their
masses and mass-to-light ratios and analyse their dynamical state with several
1D and 3D statistics. We use the spherical collapse model to study the
dynamical state of the supercluster. We show that in A2142 supercluster groups
and clusters with at least ten member galaxies lie along an almost straight
line forming a 50 Mpc/h long main body of the supercluster. The A2142
supercluster has a very high density core surrounded by lower-density outskirt
regions. The total estimated mass of the supercluster is M_est = 6.2
10^{15}M_sun. More than a half of groups with at least ten member galaxies in
the supercluster lie in the high-density core of the supercluster, centered at
the rich X-ray cluster A2142. Most of the galaxy groups in the core region are
multimodal. In the outskirts of the supercluster, the number of groups is
larger than in the core, and groups are poorer. The orientation of the cluster
A2142 axis follows the orientations of its X-ray substructures and radio halo,
and is aligned along the supercluster axis. The high-density core of the
supercluster with the global density D8 > 17 and perhaps with D8 > 13 may have
reached the turnaround radius and started to collapse. A2142 supercluster with
luminous, collapsing core and straight body is an unusual object among galaxy
superclusters. In the course of the future evolution the supercluster may be
split into several separate systems.Comment: 13 pages, 9 figures, Astronomy and Astrophysics, in press. References
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Tracing high redshift cosmic web with quasar systems
We trace the cosmic web at redshifts 1.0 <= z <= 1.8 using the quasar data
from the SDSS DR7 QSO catalogue (Schneider et al. 2010). We apply a
friend-of-friend (FoF) algorithm to the quasar and random catalogues to
determine systems at a series of linking lengths, and analyse richness and
sizes of these systems. At the linking lengths l <= 30 Mpc/h the number of
quasar systems is larger than the number of systems detected in random
catalogues, and systems themselves have smaller diameters than random systems.
The diameters of quasar systems are comparable to the sizes of poor galaxy
superclusters in the local Universe, the richest quasar systems have four
members. The mean space density of quasar systems is close to the mean space
density of local rich superclusters. At intermediate linking lengths (40 <= l
<= 70 Mpc/h) the richness and length of quasar systems are similar to those
derived from random catalogues. Quasar system diameters are similar to the
sizes of rich superclusters and supercluster chains in the local Universe. At
the linking length 70 Mpc/h the richest systems of quasars have diameters
exceeding 500 Mpc/h. The percolating system which penetrate the whole sample
volume appears in quasar sample at smaller linking length than in random
samples (85 Mpc/h). Quasar luminosities in systems are not correlated with the
system richness. Quasar system catalogues at our web pages
http://www.aai.ee/~maret/QSOsystems.html serve as a database to search for
superclusters of galaxies and to trace the cosmic web at high redshifts.Comment: 10 pages, 8 figures, accepted for publication in Astronomy and
Astrophysic
The evolution of high-density cores of the BOSS Great Wall superclusters
Context. High-density cores (HDCs) of galaxy superclusters that embed rich clusters and groups of galaxies are the earliest large objects to form in the cosmic web, and the largest objects that may collapse in the present or future.Aims. We aim to study the dynamical state and possible evolution of the HDCs in the BOSS Great Wall (BGW) superclusters at redshift z approximate to 0.5 from the CMASS (constant mass) galaxy sample, based on the Baryon Oscillation Spectroscopic Survey (BOSS) in order to understand the growth and evolution of structures in the Universe.Methods. We analysed the luminosity density distribution in the BGW superclusters to determine the HDCs in them. We derived the density contrast values for the spherical collapse model in a wide range of redshifts and used these values to study the dynamical state and possible evolution of the HDCs of the BGW superclusters. The masses of the HDCs were calculated using stellar masses of galaxies in them. We found the masses and radii of the turnaround and future collapse regions in the HDCs of the BGW superclusters and compared them with those of local superclusters.Results. We determined eight HDCs in the BGW superclusters. The masses of their turnaround regions are in the range of M-T approximate to 0.4-3.3 x 10(15) h(-1) M-circle dot, and radii are in the range of R-T approximate to 3.5-7 h(-1) Mpc. The radii of their future collapse regions are in the range of R-FC approximate to 4-8h(-1) Mpc. Distances between individual cores in superclusters are much larger: of the order of 25-35h(-)(1) Mpc. The richness and sizes of the HDCs are comparable with those of the HDCs of the richest superclusters in the local Universe.Conclusions. The BGW superclusters will probably evolve to several poorer superclusters with masses similar to those of the local superclusters. This may weaken the tension with the ACDM model, which does not predict a large number of very rich and large superclusters in our local cosmic neighbourhood, and explains why there are no superclusters as elongated as those in the BGW in the local Universe.Peer reviewe