A tomographic test of cosmic anisotropy with the recently-released quasar sample

Dong Zhao,Jun-Qing Xia

doi:10.1140/epjc/s10052-021-09701-9

Dong Zhao, Jun-Qing Xia

Open Access

https://doi.org/10.1140/epjc/s10052-021-09701-9

Copy DOI

Abstract

We test the cosmic anisotropy in the dipole-modulated Lambda CDM model and Finslerian cosmological model with the recently-released quasar sample. Based on the redshift tomographic method, the quasar sample is divided into two subsets z le z_{cut} and z > z_{cut} by different cutting redshifts. The dipole amplitudes of the two cosmological models from the subsets z le z_{cut} are very weak. We find that quasars at a higher redshift range may provide more detailed information about the dipole amplitude A_D. The dipole directions of each cosmological model from the subsets z le 1.1 and z > 1.1 are deviated by 1sigma level. The Pantheon sample is combined with the two subsets. The dipole amplitude from the two combined datasets is also very weak. In the dipole-modulated Lambda CDM model, the dipole direction from the combined dataset quasar at z le 1.1 and Pantheon sample is far away from the one given by the Pantheon sample. In the Finslerian cosmological model, the dipole directions from the two combined datasets are close to the one in the Pantheon sample.

Highlights

As one of the foundations in modern cosmology, the cosmological principle assumes that the Universe is homogeneous and isotropic at large scales [1]
The quasar sample is divided into two subsets by different cutting redshifts
In the dipole-modulated CDM model and Finslerian cosmological model, the free parameters are the matter density m, the dipole amplitude AD, the dipole direction (l, b), and the three parameters β, γ, and δ related to the quasar sample

Summary

Introduction

The low redshift observational datasets used to test cosmological models are mostly in the redshift range 0 ≤ z ≤ 2.3, such as the Type Ia supernova (SNe Ia) sample, the Hubble parameter observations, and the baryon acoustic oscillation measurements. The CDM model is barely consistent with the SNe Ia data at the redshift range z < 0.5 in the Union sample [99]. They combined the 2019 compilation of quasars [78] with the Pantheon sample [91] to test the dipole-modulated CDM model. They found that there is no evidence of cosmic anisotropy in the SN-Q sample. Zhao and Xia [83] tested the Finslerian cosmological model with the 2015 compilation of quasars. They found the cosmic anisotropy is very weak from the combination of the Pantheon sample and 2015 quasar compilation.

The quasar sample

The methodology

Results

Discussions and conclusions