Testing the anisotropy of cosmic acceleration from Pantheon supernovae sample

TL;DR

This study investigates the anisotropy of cosmic acceleration using the Pantheon supernovae sample, finding only weak anisotropy and supporting the isotropic cosmological model.

Contribution

It provides the first detailed analysis of cosmic acceleration anisotropy with the Pantheon supernovae dataset, employing hemisphere comparison and dipole fitting methods.

Findings

Dipole direction is approximately (37°, 33°) with maximum anisotropy level of 0.136.

Dipole magnitude of anisotropy is about 3.7 x 10^{-4} with a broad directional uncertainty.

Anisotropy is weak and consistent across different redshift ranges.

Abstract

In this paper, we study the anisotropy of cosmic acceleration the using Pantheon sample, which includes 1048 spectroscopically confirmed Type Ia supernovae (SNe Ia) covering the redshift range $0.01 < z < 2.3$. In hemisphere comparison method, we find the dipole direction is $(l = 37 \pm 40^{\circ}, b = 33 \pm 16^{\circ})$ with the maximum anisotropy level of $\delta=0.136 {}^{+0.009}_{-0.005}$. From the dipole fitting method, we find that the magnitude of anisotropy is $A = (3.7 {}^{+2.5}_{-3.7}) \times 10^{-4}$, and the direction of the dipole $(l = 329^{\circ}{}^{+ 101^{\circ}}_{-28^{\circ}}, b = 37^{\circ}{}^{+ 52^{\circ}}_{-21^{\circ}})$ in the galactic coordinate system. The result is weakly dependent on redshift from the redshift tomography analysis. The anisotropy is small and the isotropic cosmological model is an excellent approximation.