HEP Theory Journal Club

Baryon acoustic oscillations from the SDSS galaxies angular correlation function

Jailson Alcaniz

Observatorio Nacional & McGill

The 2-point angular correlation function, w(θ), where θ is the angular separation between pairs of galaxies, provides the transversal Baryon Acoustic Oscillation (BAO) signal almost model-independently. In this talk I will discuss current measurements of θ_BAO(z) using a large sample of luminous red galaxies in the redshift range z = [0.4,0.7] obtained from the Sloan Digital Sky Survey. Since noise and systematics can hide the BAO signature in the w-θ plane, we also discuss some model-independent criteria to localize the acoustic bump. We identify two sources of model-dependence in the analysis, namely, the value of the acoustic scale from Cosmic Microwave Background measurements and the correction in the θ_BAO(z) position due to projection effects. We describe how θ_BAO(z) measurements can provide a CMB-independent estimate of the length of the BAO feature. Constraints on the dark energy equation-of-state parameter w(z) from the θ_BAO(z) diagram are derived. We find that the standard ΛCDM model as well as some of its extensions are in good agreement with these θ_BAO(z) measurements.