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Unusual A2142 supercluster with a collapsing core: distribution of light and mass
Einasto, Maret,Gramann, Mirt,Saar, Enn,Liivamä,gi, Lauri Juhan,Tempel, Elmo,Nevalainen, Jukka,Heinä,mä,ki, Pekka,Park, Changbom,Einasto, Jaan EDP Sciences 2015 Astronomy and astrophysics Vol.580 No.-
<P>Context. Superclusters of galaxies can be used to test cosmological models of the formation and evolution of the largest structures in the cosmic web, and of galaxy and cluster evolution in superclusters. Aims. We study the distribution, masses, and dynamical properties of galaxy groups in the A2142 supercluster. Methods. 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 these regions, calculate their masses and mass-to-light ratios and analyse their dynamical state with 1D and 3D statistics. We use the spherical collapse model to study the dynamical state of the supercluster. Results. In the A2142 supercluster rich groups and clusters lie along an almost straight line forming the 50h<SUP>−1</SUP> Mpc long main body of the supercluster. The A2142 supercluster has a very high density core surrounded by lower-density outskirts. The total estimated mass of the supercluster is M<SUB>est</SUB> = 6.2 × 10<SUP>15</SUP> M<SUB>⊙</SUB>. More than a half of groups with at least ten member galaxies in the supercluster lie in the high-density core of the supercluster, centred at the X-ray cluster A2142. Most of the 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 axis of the cluster A2142 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 started to collapse. Conclusions. A2142 supercluster with collapsing core and straight body, is an unusual object among superclusters. In the course of the future evolution, the supercluster may split into several systems.</P>
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Tracing a high redshift cosmic web with quasar systems
Einasto, Maret,Tago, Erik,Lietzen, Heidi,Park, Changbom,Heinä,mä,ki, Pekka,Saar, Enn,Song, Hyunmi,Liivamä,gi, Lauri Juhan,Einasto, Jaan EDP Sciences 2014 Astronomy and astrophysics Vol.568 No.1
<P>Context. To understand the formation, evolution, and present-day properties of the cosmic web we need to study it at low and high redshifts. Aims. We trace the cosmic web at redshifts that range from 1.0 ≤ z ≤1.8 by using the quasar (QSO) data from the SDSSDR7QSO catalogue. Methods. We apply a friend-of-friend algorithm to the quasar and random catalogues to determine systems at a series of linking length and analyse richness and sizes of these systems. Results. At the linking lengths l ≤ 30 h<SUP>−1</SUP> Mpc, the number of quasar systems is larger than the number of systems detected in random catalogues, and the 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, ≈10<SUP>−7</SUP> (h<SUP>−1</SUP> Mpc)<SUP>−3</SUP>, is close to the mean space density of local rich superclusters. At intermediate linking lengths (40 ≤ l ≤70 h<SUP>−1</SUP> Mpc), 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. The percolating system, which penetrate the whole sample volume appears in a quasar sample at a smaller linking length than in random samples (85 h<SUP>−1</SUP> Mpc). At the linking length 70 h<SUP>−1</SUP> Mpc, the richest systems of quasars have diameters exceeding 500 h<SUP>−1</SUP> Mpc. Quasar luminosities in systems are not correlated with the system richness. Conclusions. Quasar system catalogues in our web pages and at the Strasbourg Astronomical Data Center (CDS) serve as a database for searching superclusters of galaxies and for tracing the cosmic web at high redshifts.</P>
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