The Cosmic Dipole in the Quaia Sample of Quasars: A Bayesian Analysis

Abstract

We present a Bayesian analysis of the Quaia sample of 1.3 million quasars as a test of the cosmological principle. This principle postulates that the universe is homogeneous and isotropic on sufficiently large scales, forming the basis of prevailing cosmological models. However, recent analyses of quasar samples have found a matter dipole inconsistent with the inferred kinematic dipole of the Cosmic Microwave Background (CMB), representing a tension with the expectations of the cosmological principle. Here, we explore various hypotheses for the distribution of quasars in Quaia, finding that the sample is influenced by selection effects with significant contamination near the galactic plane. After excising these regions, we find significant evidence that the Quaia quasar dipole is consistent with the CMB dipole, both in terms of the expected amplitude and direction. This result is in conflict with recent analyses, lending support to the cosmological principle and the interpretation that the observed dipole is due to our local departure from the Hubble flow.

14 pages, 7 figures, accepted for publication in MNRAS; updated to include published correction (2 pages, 2 figures)

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• The kinematic contribution to the cosmic number count dipole
• Resolution of the incongruency of dipole asymmetries within various large radio surveys -- implications for the Cosmological Principle
• Cosmic dipoles of active galactic nuclei at optical and radio wavelengths display much larger amplitudes than the cosmic microwave background dipole
• Cosmic dipole tensions: confronting the cosmic microwave background with infrared and radio populations of cosmological sources
• Exact model of gravitational wave and pure radiation
• Dipolar fluence distribution of statistically isotropic FERMI gamma-ray bursts
• Linear Relativistic Corrections in the Spherical Fourier-Bessel Power Spectrum
• Exploring the cosmic microwave background dipole direction using gamma-ray bursts
• Solar peculiar motion inferred from dipole anisotropy in redshift distribution of quasars appears to lie along the Galactic Centre direction
• The Ellis and Baldwin test of the Cosmic Dipole: Exploring the impact of multiple flux density cuts
• Secondary gravitational waves against a strong gravitational wave in the Bianchi VI universe
• Linear perturbations of an exact gravitational wave in the Bianchi IV universe