Detection of the velocity dipole in the radio galaxies of the NRAO VLA Sky Survey

TL;DR

This paper reports the first detection of a velocity dipole in the distribution of distant radio galaxies, confirming the standard cosmological model's prediction of our motion relative to the cosmic background.

Contribution

It provides the first observational evidence of the velocity dipole in radio galaxy distribution, aligning with the CMB dipole and supporting cosmological theories.

Findings

Dipole anisotropy detected in radio galaxy distribution

Dipole aligns with the CMB dipole direction

Amplitude of the dipole matches theoretical expectations

Abstract

We are in motion against the cosmic backdrop. This motion is evidenced by the systematic temperature shift - or dipole anisotropy - observed in the Cosmic Microwave Background radiation (CMB). Because of the Doppler effect, the temperature of the CMB is 0.1 per cent higher in our direction of motion through the Universe. If our standard cosmological understanding is correct, this dipole should also be present as an enhancement in the surface density of distant galaxies. The main obstacle in finding this signal is the very uneven distribution of nearby galaxies in the Local Supercluster, which drowns out the small cosmological imprint. Here we report the first detection of the expected dipole anisotropy in the galaxy distribution, in a survey of galaxies detected in radio waves. Radio galaxies are mostly located at cosmological distances, so the contamination from nearby clusters should be small. With local radio sources removed, we find a dipole anisotropy in the radio galaxy distribution in the same direction as the CMB, close to the expected amplitude. This result is confirmation of the standard cosmological interpretation of the CMB.