The significance of anisotropic signals hiding in the type Ia supernovae

Understand

We use two different methods, i.e., dipole-fitting (DF) and hemisphere comparison (HC), to search for the anisotropic signals hiding in the Union2.1 data set.

• We find that the directions of maximum matter density derived using these two methods are about $114^{\circ}$ away from each other.
• We construct four Union2.1-like mock samples to test the statistical significance of these two methods.
• It is shown that DF method is statistically significant, while HC method is strongly biased by the distribution of data points in the sky.