THE SLOAN GREAT WALL. MORPHOLOGY AND GALAXY CONTENT

Author(s): Einasto, M.; Liivamaegi, L. J.; Tempel, E.; et al.

Source: ASTROPHYSICAL JOURNAL  Volume: 736   Issue: 1     Article Number: 51   DOI: 10.1088/0004-637X/736/1/51   Published: JUL 20 2011

We present the results of a study of the morphology and galaxy content of the Sloan Great Wall (SGW), the richest galaxy system in the nearby universe. We use the luminosity density field to determine superclusters in the SGW, and the fourth Minkowski functional V-3 and the morphological signature (the K-1-K-2 shapefinder curve) to show the different morphologies of the SGW, from a single filament to a multibranching, clumpy planar system. We show that the richest supercluster in the SGW, SCl 126, and especially its core, resembles a very rich filament, while another rich supercluster in the SGW, SCl 111, resembles a “multispider”-an assembly of high-density regions connected by chains of galaxies. We study the substructure of individual galaxy populations determined by their color in these superclusters using Minkowski functionals and find that in the high-density core of the SGW the clumpiness of red and blue galaxies is similar, but in the outskirts of superclusters the distribution of red galaxies is clumpier than that of blue galaxies. At intermediate densities, the systems of blue galaxies have tunnels through them. We assess the statistical significance of our results using the halo model and smoothed bootstrap. We study the galaxy content and the properties of groups of galaxies in the two richest superclusters of the SGW, paying special attention to bright red galaxies (BRGs) and the first ranked (the most luminous) galaxies in SGW groups. The BRGs are the nearby luminous red galaxies; they are mostly bright and red and typically reside in groups (several groups host five or more BRGs). About one-third of the BRGs are spirals. The scatter of colors of elliptical BRGs is smaller than that of spiral BRGs. About half of the BRGs and of first ranked galaxies in groups have large peculiar velocities. Groups with elliptical BRGs as their first ranked galaxies populate superclusters more uniformly than the groups that have a spiral BRG as their first ranked galaxy. The galaxy and group content of the core of the supercluster SCl 126 shows several differences in comparison with the outskirts of this supercluster and with the supercluster SCl 111. Here, groups with BRGs are richer and have larger velocity dispersions than groups with BRGs in the outskirts of this supercluster and in SCl 111. The fraction of those BRGs that do not belong to any group is the smallest here. In the core of the supercluster SCl 126, the fraction of red galaxies is larger than in the outskirts of this supercluster or in the supercluster SCl 111. Here, the peculiar velocities of the first ranked galaxies are larger than in the outskirts of this supercluster or in the supercluster SCl 111 and the peculiar velocities of elliptical BRGs are larger than those of spiral BRGs, while in the outskirts of this supercluster and in the supercluster SCl 111 the peculiar velocities of spiral BRGs are larger than those of elliptical BRGs. All this suggests that the formation history and evolution of individual neighbor superclusters in the SGW have been different and the SGW is not a genuine physical structure but an assembly of very rich galaxy systems.