Anisotropy of the Universe via the Pantheon supernovae sample revisited

Understand

We employ the hemisphere comparison (HC) method and the dipole fitting (DF) method to investigate the cosmic anisotropy in the recently released Pantheon sample of type Ia supernovae (SNe Ia) and five combinations among Pantheon.

• For the HC method, we find the maximum anisotropy level in the full Pantheon sample is $\mathrm{AL}_{max}=0.361\pm0.070$ and corresponding direction $(l,b)=({123.05^{\circ}}^{+11.25^{\circ}}_{-4.22^{\circ}}, {4.78^{\circ}}^{+1.80^{\circ}}_{-8.36^{\circ}})$.
• A robust check shows the statistical significance of maximum anisotropy level is about $2.1\sigma$.
• We also find that the Low-$z$ and SNLS subsamples have decisive impact on the overall anisotropy while other three subsamples have little impact.