Clustering of Photometric Luminous Red Galaxies II: Cosmological Implications from the Baryon Acoustic Scale

TL;DR

This paper presents a new measurement of the angular baryon acoustic oscillation scale using photometric redshift data from SDSS Luminous Red Galaxies, providing insights into cosmological parameters and dark energy.

Contribution

First direct measurement of the angular BAO scale in galaxy distribution using photometric redshifts, confirming previous results and aiding cosmological parameter estimation.

Findings

BAO signal detected at ~2.3 sigma confidence level

Angular BAO scale measured as 3.90 ± 0.38 degrees at z=0.55

Results consistent with WMAP7 cosmology

Abstract

A new determination of the sound horizon scale in angular coordinates is presented. It makes use of ~ 0.6 x 10^6 Luminous Red Galaxies, selected from the Sloan Digital Sky Survey imaging data, with photometric redshifts. The analysis covers a redshift interval that goes from z=0.5 to z=0.6. We find evidence of the Baryon Acoustic Oscillations (BAO) signal at the ~ 2.3 sigma confidence level, with a value of theta_{BAO} (z=0.55) = (3.90 \pm 0.38) degrees, including systematic errors. To our understanding, this is the first direct measurement of the angular BAO scale in the galaxy distribution, and it is in agreement with previous BAO measurements. We also show how radial determinations of the BAO scale can break the degeneracy in the measurement of cosmological parameters when they are combined with BAO angular measurements. The result is also in good agreement with the WMAP7 best-fit cosmology. We obtain a value of w_0 = -1.03 \pm 0.16 for the equation of state parameter of the dark energy, Omega_M = 0.26 \pm 0.04 for the matter density, when the other parameters are fixed. We have also tested the sensitivity of current BAO measurements to a time varying dark energy equation of state, finding w_a = 0.06 \pm 0.22 if we fix all the other parameters to the WMAP7 best-fit cosmology.