2024ApJ...964...87Y

Recent research reveals that the Local Group is in motion toward (l, b) = (276, 30) relative to the cosmic background radiation, manifesting a velocity of 600 km s^–1, a phenomenon recognized as the cosmic background radiation dipole or cosmic microwave background dipole. Despite its well-documented nature, the precise cause of this peculiar motion remains elusive. High mass-density regions, such as galactic superclusters, stand out among the potential contributors to this cosmic flow. This paper employs chameleon fields to investigate anisotropies on both small and large scales. The data utilized in this study comprise Type Ia supernovae from the Pantheon catalog, totaling 1048 supernovae within the redshift range of 0.015 < z < 2.3. The analysis of the bulk flow at various redshifts has yielded noteworthy discoveries. On a smaller scale (less than 150 Mpc), the movement direction of the Local Group coincides with that of the bulk flow. On a larger scale, the bulk flow direction corresponds to the direction of the dark energy dipole. This implies that the anisotropy at the local scale originates from the same source as the anisotropy observed on a larger scale.