Study of baryon acoustic oscillations with SDSS DR12 data and measurements of $\Omega_k$ and $\Omega_\textrm{DE}(a)$. Part II

TL;DR

This paper introduces new BAO observables derived from SDSS DR12 data that are independent of cosmological parameters, enabling constraints on curvature and dark energy evolution, revealing some tension with flat universe models.

Contribution

It defines parameter-independent BAO observables and uses them to constrain cosmological parameters, including curvature and dark energy evolution, with SDSS data and external measurements.

Findings

Constraints on mbda_k and mbda_DE(a) from BAO data

Detection of tension with flat universe and constant dark energy models

Use of BAO observables combined with CMB and external data

Abstract

We define Baryon Acoustic Oscillation (BAO) observables $\hat{d}_\alpha(z, z_c)$, $\hat{d}_z(z, z_c)$, and $\hat{d}_/(z, z_c)$ that do not depend on any cosmological parameter. From each of these observables we recover the BAO correlation length $d_\textrm{BAO}$ with its respective dependence on cosmological parameters. These BAO observables are measured as a function of redshift $z$ with the Sloan Digital Sky Survey (SDSS) data release DR12. From the BAO measurements alone, or together with the correlation angle $\theta_\textrm{MC}$ of the Cosmic Microwave Background (CMB), we constrain the curvature parameter $\Omega_k$ and the dark energy density $\Omega_\textrm{DE}(a)$ as a function of the expansion parameter $a$ in several scenarios. These observables are further constrained with external measurements of $h$ and $\Omega_\textrm{b} h^2$. We find some tension between the data and a cosmology with flat space and constant dark energy density $\Omega_\textrm{DE}(a)$.