In search of the Local Universe dynamical homogeneity scale with CF4++ peculiar velocities

¹ Université Claude Bernard Lyon 1, IUF, IP2I Lyon, 4 Rue Enrico Fermi, 69622 Villeurbanne, France
² Centre for Astrophysics & Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia
³ ARC Centre of Excellence for Dark Matter Particle Physics, Swinburne University VIC 3122, Australia
⁴ Korea Institute for Advanced Study, 85, Hoegi-ro, Dongdaemun-gu, Seoul 02455, Republic of Korea
⁵ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China

^⋆ Corresponding author: h.courtois@ip2i.in2p3.fr

Received: 3 January 2025
Accepted: 20 June 2025

Abstract

This article explores an update to the cosmography of the local Universe within z = 0.1, incorporating galaxy peculiar velocity datasets from the first data releases of the WALLABY, FAST, and DESI surveys. The number of galaxies with peculiar velocities currently selected in each survey is 655, 4796, and 4191, respectively. The new CF4++ compendium enables a more comprehensive study of the nearby Universe bulk flow dynamics. We find a bulk flow of 315 ± 40 km s⁻¹ at 150 h⁻¹ Mpc. This analysis additionally reveals that the dynamical scale of homogeneity is not yet reached in the interval [200−300] h⁻¹ Mpc from the observer. This new data also refines the structure of local superclusters, revealing more spherical shapes and more clearly defined boundaries for key regions such as the Great Attractor (Laniakea) and the Coma cluster. The addition of a few measurements has made a big difference in our ability to reveal the hidden Vela supercluster. To help colleagues obtain a peculiar velocity prediction for the object they are currently studying (e.g. SNIa, gravitational waves), we publicly release the CF4++ catalogue, as well as the reconstructed density and velocity fields used in this work.