Skewness as a probe of Baryon Acoustic Oscillations

TL;DR

This paper demonstrates that the skewness of the cosmic density field can serve as a clean, low-systematic probe of Baryon Acoustic Oscillations, potentially aiding dark energy studies.

Contribution

It introduces skewness as a novel, less biased statistic for detecting BAO features, with theoretical evaluation of its effectiveness across cosmological models.

Findings

Skewness contains a detectable BAO signal at smaller scales (~82 Mpc/h).

BAO wiggle amplitude in skewness is about 3%.

Skewness is less sensitive to bias and redshift distortions.

Abstract

In this study we show that the skewness S_3 of the cosmic density field contains a significant and potentially detectable and clean imprint of Baryonic Acoustic Oscillations. Although the BAO signal in the skewness has a lower amplitude than second order measures like the two-point correlation function and power spectrum, it has the advantage of a considerably lower sensitivity to systematic influences. Because it lacks a direct dependence on bias if this concerns simple linear bias, skewness will be considerably less beset by uncertainties due to galaxy bias. Also, it has a weaker sensitivity to redshift distortion effects. We use perturbation theory to evaluate the magnitude of the effect on the volume-average skewness, for various cosmological models. One important finding of our analysis is that the skewness BAO signal occurs at smaller scales than that in second order statistics. For an LCDM spectrum with WMAP7 normalization, the BAO feature has a maximum wiggle amplitude of ~3% and appears at a scale of ~82Mpc/h. We conclude that the detection of BAO wiggles in future extensive galaxy surveys via the skewness of the observed galaxy distribution may provide us with a useful, and potentially advantageous, measure of the nature of Dark Energy.