Isotropic vs. Anisotropic components of BAO data: a tool for model selection

Abstract

We conduct a selective analysis of the isotropic ($D_V$) and anisotropic ($AP$) components of the most recent Baryon Acoustic Oscillations (BAO) data. We find that these components provide significantly different constraints and could provide strong diagnostics for model selection, also in view of more precise data to arrive. For instance, in the $\Lambda$CDM model, we find a mild tension of $\sim 2 \sigma$ for the $\Omega_m$ estimates obtained using $D_V$ and $AP$ separately. Considering both $\Omega_k$ and $w$ as free parameters, we find that the concordance model is in tension with the best-fit values provided by the BAO data alone at 2.2$\sigma$. We complemented the BAO data with the Supernova Ia (SNIa) and Observational \textit{Hubble} datasets to perform a joint analysis on the $\Lambda$CDM model and its standard extensions. By assuming $\Lambda$CDM scenario, we find that these data provide $H_0 = 69.4 \pm 1.7$ \text{km/s Mpc$^{-1} $} as the best-fit value for the present expansion rate. In the $k\Lambda$CDM scenario we find that the evidence for acceleration using the BAO data alone is more than $\sim 5.8\sigma$, which increases to $8.4 \sigma$ in our joint analysis.