Dynamic cosmography of the local Universe: Laniakea and five more watershed superclusters

TL;DR

This paper maps the dynamical structure of the local Universe within z=0.1, identifying superclusters and voids as watersheds based on gravitational velocity fields, revealing larger-than-expected structures compared to cosmological models.

Contribution

It introduces a novel dynamical definition of superclusters and voids using gravitational velocity fields, providing detailed size, shape, and matter flow information for multiple superclusters.

Findings

Laniakea supercluster size confirmed at 2 million Mpc^3

Five additional superclusters dynamically characterized

Observed superclusters are larger than ΛCDM predictions

Abstract

This article delivers the dynamical cosmography of the Local Universe within z=0.1 (1 giga light-years). We exploit the gravitational velocity field computed using the CosmicFlows-4 catalog of galaxy distances to delineate superclusters as watersheds, publishing for the first time their size, shape, main streams of matter and the location of their central attractor. Laniakea, our home supercluster's size is confirmed to be 2 $\times 10^6$ (Mpc $h^{-1}$)$^3$. Five more known superclusters are now dynamically defined in the same way: Apus, Hercules, Lepus, Perseus-Pisces and Shapley. Also, the central repellers of the Bootes and Sculptor voids are found and the Dipole and Cold Spot repellers now appear as a single gigantic entity. Interestingly the observed superclusters are an order of magnitude larger than the theoretical ones predicted by cosmological $\Lambda$CDM simulations.