On the isotropy of SnIa absolute magnitudes in the Pantheon+ and SH0ES samples

Understand

We use the hemisphere comparison method to test the isotropy of the SnIa absolute magnitudes of the Pantheon+ and SH0ES samples in various redshift/distance bins.

• We compare the identified levels of anisotropy in each bin with Monte-Carlo simulations of corresponding isotropised data to estimate the frequency of such levels of anisotropy in the context of an underlying isotropic cosmological.
• We find that the identified levels of anisotropy in all bins are consistent with the Monte-Carlo isotropic simulated samples.
• However, in the real samples for both the Pantheon+ and the SH0ES cases we find sharp changes of the level of anisotropy occuring at distances less than $40Mpc$.