2025/04/01 by Rahima Mokeddem, Maria Lopes, Mokeddem, Rahima +7 · 2 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae
paper · pdf · doi:10.48550/arxiv.2504.00903
In this study we investigate potential large-angle anisotropies in the angular distribution of the cosmological parameters H0 (the Hubble constant) and Ωm (the matter density) in the flat-ΛCDM framework, using the Pantheon+SH0ES supernovae catalog. For this we perform a directional analysis by dividing the celestial sphere into a set of directions, and estimate the best-fit cosmological parameters across the sky using a MCMC approach. Our results show a dominant dipolar pattern for both parameters in study, suggesting a preferred axis in the universe expansion and in the distribution of matter. However, we also found that for z \gtrsim 0.015, this dipolar behavior is not statistically significant, confirming the expectation -- in the ΛCDM scenario -- of an isotropic expansion and a uniform angular distribution of matter (both results at 1 σ confidence level). Nevertheless, for nearby supernovae, at distances \lesssim 60 Mpc or z \lesssim 0.015, the peculiar velocities introduce a highly significant dipole in the angular distribution of H0. Furthermore, we perform various robustness tests that support our findings, and consistency tests of our methodology.