The Universe is Brighter in the Direction of Our Motion: Galaxy Counts and Fluxes are Consistent with the CMB Dipole

TL;DR

This study demonstrates that galaxy counts and fluxes align with the CMB dipole, confirming that galaxies are generally at rest relative to the early universe, thus supporting standard cosmological models.

Contribution

The paper provides observational evidence that galaxy distributions are consistent with the CMB dipole, resolving previous claims of excess galaxy counts and fluxes in the motion direction.

Findings

Galaxy counts and fluxes match the CMB dipole in direction and velocity.

Estimated dipole velocity is consistent with the CMB-derived velocity.

Results support the standard cosmological model with galaxies at rest relative to the early universe.

Abstract

An observer moving with respect to the cosmic rest frame should observe a concentration and brightening of galaxies in the direction of motion and a spreading and dimming in the opposite direction. The velocity inferred from this dipole should match that of the cosmic microwave background (CMB) temperature dipole if galaxies are on average at rest with respect to the CMB rest frame. However, recent studies have claimed a many-fold enhancement of galaxy counts and flux in the direction of the solar motion compared to the CMB expectation, calling into question the standard cosmology. Here we show that the sky distribution and brightness of extragalactic radio sources are consistent with the CMB dipole in direction and velocity. We use the first epoch of the Very Large Array Sky Survey combined with the Rapid Australian Square Kilometer Array Pathfinder Continuum Survey to estimate the dipole via several different methods, and all show similar results. Typical fits find a $331^{+161}_{-107}$ km s$^{-1}$ velocity dipole with apex $(\ell,b) = (271^{+55}_{-58}, 56^{+13}_{-35})$ in Galactic coordinates from source counts and $399^{+264}_{-199}$ km s$^{-1}$ toward $(\ell,b) = (301^{+30}_{-30}, 43^{+19}_{-17})$ from radio fluxes. These are consistent with the CMB-solar velocity, 370 km s$^{-1}$ toward $(\ell,b) = (264, 48)$, and show that galaxies are on average at rest with respect to the rest frame of the early universe, as predicted by the canonical cosmology.