Study of baryon acoustic oscillations with SDSS DR12 data and measurement of $\Omega_\textrm{DE}(a)$

TL;DR

This paper introduces new BAO distance measures from SDSS DR12 data, constrains cosmological parameters, finds tension with flat, constant dark energy models, and measures the evolution of dark energy density.

Contribution

It defines parameter-independent BAO distances and uses them to test cosmological models against SDSS data, revealing tensions with standard assumptions.

Findings

Detected 4.3 sigma tension with flat, constant dark energy models.

Measured the evolution of dark energy density  as a function of scale factor.

Demonstrated that relaxing certain constraints aligns models with observations.

Abstract

We define Baryon Acoustic Oscillation (BAO) distances $\hat{d}_\alpha(z, z_c)$, $\hat{d}_z(z, z_c)$, and $\hat{d}_/(z, z_c)$ that do not depend on cosmological parameters. These BAO distances are measured as a function of redshift $z$ with the Sloan Digital Sky Survey (SDSS) data release DR12. From these BAO distances alone, or together with the correlation angle $\theta_\textrm{MC}$ of the Cosmic Microwave Background (CMB), we constrain the cosmological parameters in several scenarios. We find $4.3 \sigma$ tension between the BAO plus $\theta_\textrm{MC}$ data and a cosmology with flat space and constant dark energy density $\Omega_\textrm{DE}(a)$. Releasing one and/or the other of these constraints obtains agreement with the data. We measure $\Omega_\textrm{DE}(a)$ as a function of $a$.