Assess the robustness of the negative-SGX feature under unified uncertainty modeling

Determine whether the negative-SGX feature in the Cosmicflows-4 large-scale velocity field survives a unified treatment of observational and cosmological uncertainties, including selection effects, correlated calibration and repeated-measurement errors, nonlinear velocity covariance, and an exact distance likelihood.

Background

The analysis identifies a localized excess coherent motion at approximately 100–150 h−1 Mpc, concentrated toward negative supergalactic X (SGX). Its significance depends on catalog composition, angular window, monopole treatment, distance-scale assumptions, and the covariance model used for measurement and cosmic-velocity uncertainties.

The authors state that a selection-matched mock-catalog analysis with predefined summary statistics, nonlinear velocity covariance, correlated calibration and repeated-measurement errors, and an exact distance likelihood is needed to assess whether the observed feature is robust. This remains unresolved because the present analysis does not incorporate all of these effects simultaneously.