Identification of Basins of Attraction in the Local Universe

TL;DR

This paper reconstructs the large-scale structure of the Universe using galaxy data and a Hamiltonian Monte-Carlo method, identifying basins of attraction and revealing their sizes and associations with known cosmic features.

Contribution

It introduces a probabilistic method to identify and analyze basins of attraction in the Universe's structure using the latest Cosmicflows-4 data.

Findings

Laniakea is likely part of the larger Shapley basin of attraction.

The Sloan Great Wall is associated with the largest basin of attraction.

The largest basin covers over 15 million cubic megaparsecs.

Abstract

Structure in the Universe is believed to have evolved out of quantum fluctuations seeded by inflation in the early Universe. These fluctuations lead to density perturbations that grow via gravitational instability into large cosmological structures. In the linear regime, the growth of structure is directly coupled to the velocity field since perturbations are amplified by attracting (and accelerating) matter. Surveys of galaxy redshifts and distances allow one to infer the underlying density and velocity fields. Here, assuming the LCDM standard model of cosmology and applying a Hamiltonian Monte-Carlo algorithm to the grouped Cosmicflows-4 (CF4) compilation of 38,000 groups of galaxies, the large scale structure of the Universe is reconstructed out to a redshift corresponding to about 30, 000 km/s. Our method provides a probabilistic assessment of the domains of gravitational potential minima: basins of attraction (BoA). Earlier Cosmicflows catalogs suggested the Milky Way Galaxy was associated with a BoA called Laniakea. Now with the newer CF4 data, there is a slight probabilistic preference for Laniakea to be part of the much larger Shapley BoA. The largest BoA recovered from the CF4 data is associated with the Sloan Great Wall with a volume within the sample of 15.5 10^6(Mpc/h)^3, which is more than twice the size of the second largest Shapley BoA.