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

TL;DR

This paper analyzes isotropic and anisotropic BAO data components separately, revealing their different constraints and potential for model selection, and assesses their implications for cosmological parameters and the acceleration of the universe.

Contribution

It introduces a comparative analysis of BAO data components for improved model diagnostics and combines multiple datasets to refine cosmological parameter estimates.

Findings

Isotropic and anisotropic BAO components provide different constraints.

Tension of ~2σ between Ω_m estimates from D_V and AP.

BAO data alone indicates universe acceleration at >5.8σ significance.

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.