Ultra-compact radio sources and the isotropy and homogeneity of the Universe

Abstract

A 2.29 GHz VLBI all-sky survey of ultra-compact radio sources has formed the basis of a number of cosmological investigations, which examine the relationship between angular-size and redshift. Here I use a sample of 468 such sources with 0.5<z<=3.787, to investigate the isotropy of the Universe. The sample is divided into hemispherical sub-samples, over an all-sky 5 degree x 5 degree array, each of which is allowed to determine a value of Omega_m, assuming that we are living in a spatially flat homogeneous isotropic LambdaCDM model. If we regard the latter as a null hypothesis, then it fails the test -- the results show significant anisotropy, the smallest value of Omega_m being towards (l,b)=(253.9,24.1) degrees, the largest in the opposite direction. This is close to the CMB dipole axis, but in the obverse sense. This is interpreted as meaning that the Universe is not spatially homogeneous on the largest scales, and is better represented at late times by a spherically symmetric model with a density enhancement at its centre.

13 pages, 7 figures

References in corpus (2)

• Spectra and Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation
• Legacy data and cosmological constraints from the angular-size/redshift relation for ultra-compact radio sources

Cited by in corpus (19)

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• Constraints on anisotropic cosmic expansion from supernovae
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• Testing the Copernican principle by constraining spatial homogeneity
• Testing the Etherington's distance duality relation at higher redshifts: the combination of radio quasars and gravitational waves
• Testing the distance duality relation using type Ia supernovae and ultracompact radio sources
• The Copernican principle in light of the latest cosmological data
• Inflation and primordial power spectra at anisotropic spacetime inspired by Planck's constraints on isotropy of CMB
• Constraining the Anisotropy of the Universe from Supernovae and Gamma-ray Bursts
• Testing isotropy in the Universe using photometric and spectroscopic data from the SDSS
• Constraints on dark energy from the Lyα forest baryon acoustic oscillations measurement of the redshift 2.3 Hubble parameter
• Testing cosmic anisotropy with Pade approximation and Pantheon+ sample
• Observational constraints on dark energy cosmological model parameters
• Probing large scale homogeneity and periodicity in the LRG distribution using Shannon entropy
• A new method for testing isotropy with Shannon entropy
• Testing isotropy in the Two Micron All-Sky redshift survey with information entropy
• Pseudo-Evolution of Galaxies in LCDM Cosmology
• The failure of testing for cosmic opacity via the distance-duality relation