Abstract:
The large-scale structure of the Universe comprising of galaxies and dark
matter has a web-like geometry which is called the 'Cosmic Web'. Its main
constituents are walls, filaments, clusters, and voids. The galaxy redshift
surveys have shown that there are structures present on even larger scales
than clusters and these are called the superclusters (clusters of galaxy clusters). Massive superclusters are the largest structures found in the Universe
and they are rare. The properties of superclusters can be used to test various
cosmological models while there are still unknowns how superclusters form
and evolve.
In this thesis, we present the discovery of a massive, 200 Mpc (Megaparsecs) scale supercluster, the Saraswati, at redshift of 0.28. Saraswati is
one of the most massive superclusters with at least 43 galaxy clusters and
a total mass of ~ 2 x 10^16 M_sun (solar masses). We also present a catalog of
superclusters, identified using the data on clusters, in the redshift range of
0.05 <= z <= 0.42. This is the largest catalog of superclusters (571 superclusters) in this redshift range having a range of masses and sizes with the most
massive supercluster being at z ~ 0.12 containing 59 clusters within ~ 170
Mpc. Our new catalog of superclusters is useful for the statistical studies of
their properties. With a goal to understand the relation between overdensities (dominated by dark matter) and under-densities (dominated by dark
energy), we have extracted voids and high-density regions from the Sloan
Digital Sky Survey. Using the Watershed and Voronoi tessellation methods,
we measured their two-point correlation functions. This study has led to the
understanding of the high correlation scales among voids and high-density
regions and their physical inter-relationship.
