A large anisotropy in the sky distribution of 3CRR quasars and other radio galaxies

TL;DR

This study reveals significant anisotropies in the sky distribution of 3CRR quasars and radio galaxies, challenging the assumption of isotropy in the universe and raising questions about large-scale inhomogeneities and cosmological principles.

Contribution

It provides the first evidence of large-scale anisotropies in the distribution of powerful radio sources, suggesting potential violations of the cosmological principle.

Findings

33 of 48 quasars in one half of the sky

Probability of such anisotropy by chance is ~1%

Combined anisotropies probability is ~2×10^{-5}

Abstract

We report the presence of large anisotropies in the sky distributions of powerful extended quasars as well as some other sub-classes of radio galaxies in the 3CRR survey, the most reliable and most intensively studied complete sample of strong steep-spectrum radio sources. The anisotropies lie about a plane passing through the equinoxes and the north celestial pole. Out of a total of 48 quasars in the sample, 33 of them lie in one half of the observed sky and the remaining 15 in the other half. The probability that in a random distribution of 3CRR quasars in the sky, statistical fluctuations could give rise to an asymmetry in observed numbers up to this level is only $\sim 1\%$. Also only about 1/4th of Fanaroff-Riley 1 (FR1) type of radio galaxies lie in the first half of the observed sky and the remainder in the second half. If we include all the observed asymmetries in the sky distributions of quasars and radio galaxies in the 3CRR sample, the probability of their occurrence by a chance combination reduces to $\sim 2 \times 10^{-5}$. Two pertinent but disturbing questions that could be raised here are -- firstly why should there be such large anisotropies present in the sky distribution of some of the strongest and most distant discrete sources, implying inhomogeneities in the universe at very large scales (covering a fraction of the universe)? Secondly why should such anisotropies lie about a great circle decided purely by the orientation of earth's rotation axis and/or the axis of its revolution around the sun? Are these alignments a mere coincidence or do they imply that these axes have a preferential placement in the larger scheme of things, implying an apparent breakdown of the Copernican principle or its more generalization, cosmological principle, upon which the standard cosmological model is based upon?