Abstract Details
| Name: Joydeep Bagchi Affiliation: Inter University Centre for Astronomy & Astrophysics (IUCAA) Conference ID: ASI2017_1325 Title : Saraswati: An Extremely Massive ~200 Megaparsec Scale Supercluster Authors and Co-Authors : Shishir Sankhyayan (IISER, Pune) Prakash Sarkar (NIT, Jamshedpur) Somak Raychaudhury (IUCAA, Pune) Joe Jacob (Newman College, Thodupuzha) Pratik Dabhade (IUCAA, Pune) Abstract Type : Oral Abstract Category : General Relativity and Cosmology Abstract : Superclusters of galaxies are believed to be the largest concentrations of matter in the Universe whose origin is still debated. I will report the discovery of an extremely massive and large-scale super cluster (called `Saraswati') found in SDSS spectroscopic survey. It shows a vast concentration of galaxies and galaxy clusters forming a wall-like structure spanning at least 200~Mpc across at the redshift z ~0.3. This enormous structure is surrounded by a network of lesser galaxy filaments, clusters and large (~20 - 150 Mpc) voids. The density contrast (delta) relative to mean matter density of the Universe of `Saraswati' is >1.62 and the densest region of this supercluster comprises at least 43 massive galaxy clusters with total mass of 2 X 10^{16} M_sun and a bound core of ~20 Mpc. This places `Saraswati' among the few largest, most massive superclusters known till date, comparable to the extremely massive `Shapley Concentration' (z = 0.046) in the local universe. The `Saraswati' supercluster and its environs reveal that some extreme large scale, prominent matter density enhancements had already formed ~4 Gy in the past eon when dark-energy had just started to dominate structure formation. I will discuss how this large galactic over density helps understand the role of dark energy and cosmological initial conditions in supercluster formation, and tests the competing cosmological models. |