Dipole Mapping of the Local Hubble Expansion

Dipole mapping of the local Hubble expansion analyzes the low-redshift Pantheon+SH0ES Type Ia supernova sample (up to z_HD ≤ 0.10) as a directional residual field on the sky. We fit Hubble-diagram residuals with generalized least squares using the full statistical+systematic covariance, decomposing the signal into an isotropic monopole, a kinematic dipole scaling as 1/z, and a redshift-independent constant-amplitude dipole (“TEX”). Footprint-aware, whitened permutation tests quantify significance while accounting for direction fitting and survey geometry. Tomographic shell fits reveal a localized radial peak of the constant-amplitude component, motivating a minimal redshift floor to preserve interior–shell–exterior contrast on the real footprint. The results provide an empirical “dipole budget” framework for interpreting local anisotropy in nearby H₀ determinations.