2026MNRAS.545f1960S -
Mon. Not. R. Astron. Soc., 545, part no 6, 1960 (2026/January-2)
The Velocity Field Olympics: assessing velocity field reconstructions with direct distance tracers.
STISKALEK R., DESMOND H., DEVRIENDT J., SLYZ A., LAVAUX G., HUDSON M.J., BARTLETT D.J. and COURTOIS H.M.
Abstract (from CDS):
The peculiar velocity field of the local Universe provides direct insights into its matter distribution and the underlying theory of gravity, and is essential in cosmological analyses for modelling deviations from the Hubble flow. Numerous methods have been developed to reconstruct the density and velocity fields at $z \lesssim 0.05$, typically constrained by redshift-space galaxy positions or by direct distance tracers such as the Tully-Fisher relation, the Fundamental Plane, or Type Ia supernovae. We introduce a validation framework to evaluate the accuracy of these reconstructions against catalogues of direct distance tracers. Our framework assesses the goodness-of-fit of each reconstruction using Bayesian evidence, residual redshift discrepancies, velocity scaling, and the need for external bulk flows. Applying this framework to a suite of reconstructions - including those derived from the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm and from linear theory - we find that the non-linear BORG reconstruction consistently outperforms others. We highlight the utility of such a comparative approach for supernova or gravitational wave cosmological studies, where selecting an optimal peculiar velocity model is essential. Additionally, we present calibrated bulk flow curves predicted by the reconstructions and perform a density-velocity cross-correlation using a linear theory reconstruction to constrain the growth factor, yielding $S_8 = 0.793 \pm 0.035$. The result is in good agreement with both weak lensing and Planck, but is in strong disagreement with some peculiar velocity studies.
Abstract Copyright:
© The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society.
Journal keyword(s):
galaxies: distances and redshifts - distance scale - large-scale structure of Universe
Simbad objects:
6
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