Is the local Hubble flow consistent with concordance cosmology?

TL;DR

This study investigates whether the local Hubble flow aligns with the standard cosmological model by analyzing redshift data and predicting Doppler effects using linear perturbation theory, finding consistency with the concordance model at certain scales.

Contribution

The paper demonstrates that linear perturbation theory can effectively predict Doppler effects on redshifts and distances, and confirms the consistency of local Hubble flow measurements with the concordance cosmology.

Findings

Data at 20-150 Mpc is consistent with the concordance model.

Linear analysis captures key aspects of nonlinear structure effects.

Differences in measured Hubble constants depend only on observer relative velocity.

Abstract

Yes. In a perturbed Friedmann model, the difference of the Hubble constants measured in two rest-frames is independent of the source peculiar velocity and depends only on the relative velocity of the observers, to lowest order in velocity. Therefore this difference should be zero when averaging over sufficient sources, which are at large enough distances to suppress local nonlinear inhomogeneity. We use a linear perturbative analysis to predict the Doppler effects on redshifts and distances. Since the observed redshifts encode the effect of local bulk flow due to nonlinear structure, our linear analysis is able to capture aspects of the nonlinear behaviour. Using the largest available distance compilation from CosmicFlows-3, we find that the data is consistent with simulations based on the concordance model, for sources at $20-150\,$Mpc.