Saraswati: An Extremely Massive ∼200 Megaparsec Scale Supercluster

Journal Article · Thu Jul 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA7949· OSTI ID:22876010

Bagchi, Joydeep; Raychaudhury, Somak; Dabhade, Pratik ^[1]; Sankhyayan, Shishir ^[2]; Sarkar, Prakash ^[3]; Jacob, Joe ^[4]

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1. The Inter-University Centre for Astronomy and Astrophysics (IUCAA), S.P. Pune University Campus, Post Bag 4, Pune 411007 (India)
2. Indian Institute of Science Education and Research (IISER), Dr. Homi Bhabha Road, Pashan, Pune 411008 (India)
3. Dept. of Physics, National Institute of Technology (NIT), NIT Campus, P.O. RIT, Jamshedpur 831014 (India)
4. Department of Physics, Newman College, Thodupuzha 685585 (India)

Here we report the discovery of an extremely massive and large supercluster (called Saraswati{sup 5}) found in the Stripe 82 region of SDSS. This supercluster is a major concentration of galaxies and galaxy clusters, forming a wall-like structure spanning at least 200 Mpc across at redshift z≈0.3. This enormous structure is surrounded by a network of galaxy filaments, clusters, and large, ∼40–170 Mpc diameter, voids. The mean density contrast δ (relative to the background matter density of the universe) of Saraswati is ≳1.62 and the main body of the supercluster comprises at least 43 massive galaxy clusters (mean z = 0.28) with a total mass of ∼2×10{sup 16} M{sub ⊙}. The spherical collapse model suggests that the central region of radius ∼20 Mpc and mass at least 4×10{sup 15} M{sub ⊙} may be collapsing. This places it among the few largest and most massive superclusters known, comparable to the most massive “Shapley Concentration” (z≈0.046) in the nearby universe. The Saraswati supercluster and its environs reveal that some extreme large-scale, prominent matter density enhancements formed ∼4 Gyr in the past when dark energy had just started to dominate structure formation. This galactic concentration sheds light on the role of dark energy and cosmological initial conditions in supercluster formation, and tests the competing cosmological models.

• OSTI ID: 22876010
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 844; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPARATIVE EVALUATIONS
CONCENTRATION RATIO
COSMOLOGICAL MODELS
COSMOLOGY
GALAXIES
GALAXY CLUSTERS
MASS
NONLUMINOUS MATTER
RED SHIFT
UNIVERSE