Description
The Hubble tension is a significant (~4 sigma) discrepancy between the universe's expansion rate measured from supernovae and the rate predicted by the standard ΛCDM cosmological model based on CMB observations. Inspired by this tension, more detailed analyses of late-universe data have also revealed possible large-scale variation in the redshift–distance relationship across the sky, based on measurements from various sources including supernovae, strong lenses and galaxies. In this talk we focus on the anisotropy in the distance--redshift relation of clusters at z~0.1, as measured by the normalisations of various scaling relations linking their properties. This anisotropy forms a dipole pattern, the axis of which is approximately aligned with the CMB dipole, the anomalous bulk flow of CosmicFlow-4, and the anomalous matter dipole seen in high-redshift quasars. I will present the early stages of a Bayesian hierarchical model reanalysing these results, with the aim of accounting self-consistently for all relevant systematics including the joint intrinsic distributions of the clusters' properties. I will show preliminary results indicating that there is in fact no dipole in the expansion rate from these observations, and discuss implications for the Hubble tension.
