Hidden Vela Supercluster Revealed by First Hybrid Redshift & Peculiar Velocity Reconstruction

TL;DR

This paper introduces a hybrid reconstruction method combining galaxy peculiar velocities and new redshift data, revealing the Vela supercluster as a major mass concentration in the southern Galactic plane, significantly enhancing our understanding of large-scale cosmic structures.

Contribution

The study develops a novel hybrid approach integrating peculiar velocities and redshifts, including new MeerKAT HI data, to map the obscured large-scale structures in the Zone of Avoidance.

Findings

Vela supercluster is a dominant mass concentration rivaling Shapley and Laniakea.

The hybrid method uncovers the Vela supercluster's mass of 33.8 x 10^16 M_sun.

The approach provides a more complete picture of the southern Zone of Avoidance.

Abstract

A large fraction of the extragalactic sky is obscured by foreground dust and stars along the plane of the Milky Way, leaving a major gap (~ 20%) in whole-sky maps of large-scale structures -- an incompleteness that is even more severe for peculiar velocity samples. This has long limited an unambiguous interpretation of observed cosmic flows and their connection to the underlying mass-density field. We present a new hybrid reconstruction methodology which combines 65,518 galaxy peculiar velocity distances from the CF4++ catalogue (Courtois2025) with 8283 new galaxy redshifts observed near the southern Galactic plane (|b| <= 10 degrees) Zone of Avoidance. A major advance is the inclusion of 2176 high-sensitivity, interferometric HI redshifts obtained with the SARAO MeerKAT telescope which for the first time provide coverage of the innermost 3degrees-wide strip of the southern ZOA and to unprecedented depth. This hybrid redshifts & peculiar velocities approach yields a substantially revised view of the inferred overdensities in and around the ZOA. In particular, the Vela supercluster emerges as a dominant mass concentration, rivaling the Shapley concentration and exceeding the mass associated with Laniakea and the Great Attractor region. With a total mass of 33.8 10^16 Msol, a characteristic radius of 70 hmpc, and a double core morphology at a distance of 189 hmpc, Vela dominates the mass budget and gravitational influence of the southern Zone of Avoidance. These results provide the most complete and dynamically consistent picture to date of the southern Zone of Avoidance and demonstrate the transformative potential of hybrid reconstruction techniques tailored for the next generation of large-scale surveys.