Non-linear structure formation and the acoustic scale

TL;DR

This paper measures the nonlinear effects on the acoustic scale in cosmological data, demonstrating that shifts are predictable and can be mitigated with reconstruction techniques, ensuring reliable distance measurements for cosmology.

Contribution

It provides high-precision measurements of the nonlinear shifts in the acoustic scale and shows that simple reconstruction methods effectively reduce these shifts, improving cosmological distance estimates.

Findings

Nonlinear shifts in the acoustic scale are up to 0.45% at z=0.3.

Reconstruction reduces shifts to less than 0.1%.

The inferred distance ratio remains robust despite modeling variations.

Abstract

We present high signal-to-noise measurements of the acoustic scale in the presence of nonlinear growth and redshift distortions using 320(Gpc/h)^3 of cosmological PM simulations. Using simple fitting methods, we obtain robust measurements of the acoustic scale with scatter close to that predicted by the Fisher matrix. We detect and quantify the shift in the acoustic scale by analyzing the power spectrum: we detect at greater than 5 sigma a decrease in the acoustic scale in the real-space matter power spectrum of 0.2% at z=1.5, growing to 0.45% at z=0.3. In redshift space, the shifts are about 25% larger: we detect a decrease of 0.25% of at z=1.5 and 0.54% at z=0.3. Despite the nonzero amounts, these shifts are highly predictable numerically, and hence removable within the standard ruler analysis of clustering data. Moreover, we show that a simple density-field reconstruction method substantially reduces the scatter and nonlinear shifts of the acoustic scale measurements: the shifts are reduced to less than 0.1% at z=0.3-1.5, even in the presence of non-negligible shot noise. Finally, we show that the ratio of the cosmological distance to the sound horizon that would be inferred from these fits is robust to variations in the parameterization of the fitting method and reasonable differences in the template cosmology.