A Model-independent Test of Cosmic Isotropy with Low-z Pantheon Supernovae

TL;DR

This study tests the assumption of cosmic isotropy using low-redshift Pantheon supernova data in a model-independent way, finding no significant anisotropy and supporting the cosmological principle.

Contribution

It provides a model-independent analysis of cosmic isotropy with the latest supernova data, confirming the absence of anisotropy at low redshifts.

Findings

Data favors cosmic isotropy over anisotropy.

Observed anisotropy is due to nonuniform sky coverage.

Results support the cosmological principle at low redshifts.

Abstract

The assumption of homogeneity and isotropy on large scales is one of the main hypotheses of the standard cosmological model. In this paper, we revisit a test of cosmological isotropy using type Ia supernova (SN Ia) distances provided by the latest SN Ia compilation available, namely, the Pantheon compilation. We perform a model-independent analysis by selecting low-redshift subsamples lying in two redshift intervals, i.e., z $\leq$ 0.10 and z $\leq$ 0.20. By mapping the directional asymmetry of cosmological parameters across the sky, we show that the current SN Ia data favor the hypothesis of cosmic isotropy, as the anisotropy found in the maps can be mostly ascribed to the nonuniform sky coverage of the data rather than an actual cosmological signal. These results confirm that there is null evidence against the cosmological principle in the low-redshift universe.