Saraswati: An Extremely Massive ∼200 Megaparsec Scale Supercluster

Abstract

Here we report the discovery of an extremely massive and large supercluster (called Saraswati a) ) 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 the 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 ∼ 2×1016 M ⊙ . The spherical collapse model suggests that the central region of radius ∼ 20 Mpc and mass at least 4 × 10 15 M ⊙ 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 had formed ∼ 4 Gy 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.

A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy cluster

“…Cluster mergers are highly dynamical processes (Sarazin 2002), and numerous, heterogeneous merger episodes (Ferrari et al 2006;Poole et al 2006) are considered to be the most natural physical processes for disturbing both their cool-core and relaxed structure. Even in the present age, clusters are constantly growing by matter accretion at the nodes of large scale filaments of galaxies (Springel et al 2005;Dolag et al 2008;Tempel et al 2014;Bagchi et al 2017).…”

Traces of Anisotropic Quasi-Regular Structure in the SDSS Data

“…To our knowledge, up to now a few Great Walls have been reliably established, and their number is constantly growing. These are the CfA Great Wall [56], Sloan Great Wall [57,58], BOSS Great Wall [59] and Saraswati wall-like structure [60]. One can also refer to such objects as the supergalactic plane [61] in the local Universe, as well as the Sharpley Supercluster (e.g., [62,63]), and the recently revealed South Pole Wall [64].…”

“…In this regard, the question arises about the largest allowable scales of cosmological structures (huge superclusters and voids between them) consistent with the generally accepted ΛCDM cosmological model (e.g., [60]) with its extensive observation base. A possible answer to this question was given in [65], where it was shown that the largest structures of relatively low density can reach several hundred Megaparsecs without conflicting with the isotropy and uniformity of the ΛCDM model.…”

Third-Generation Calibrations for MeerKAT Observation

“…In this paper, we show the importance of the third-generation calibration (3GC, [11]) on wide field-of-view (FOV) radio interferometry observations, for example, the Saraswati supercluster [12]. In radio astronomy, subsequent developments in calibration and imaging techniques have enhanced our knowledge of the radio universe.…”