The Acoustic Peak in the Lyman Alpha Forest

TL;DR

This paper presents the first simulation of baryonic acoustic oscillations in Lyman alpha forest data with mock quasar sight-lines, demonstrating the potential for large-scale dark matter mapping and BAO detection.

Contribution

It introduces a simulation approach for BAO detection in Lyman alpha forest data using dark-matter only simulations and the fluctuating Gunn-Peterson approximation.

Findings

Lyman alpha flux traces dark matter on large scales.

Redshift space distortions are well modeled by linear theory.

Fluctuating photo-ionizing backgrounds affect large-scale power but not the BAO peak position.

Abstract

We present the first simulation of the signature of baryonic acoustic oscillations (BAO) in Lyman alpha forest data containing 180,000 mock quasar sight-lines. We use eight large dark-matter only simulations onto which we paint the Lyman alpha field using the fluctuating Gunn-Peterson approximation. We argue that this approach should be sufficient for the mean signature on the scales of interest. Our results indicate that Lyman alpha flux provides a good tracer of the underlying dark matter field on large scales and that redshift space distortions are well described by a simple linear theory prescription. We compare Fourier and configuration space approaches to describing the signal and argue that configuration space statistics provide useful data compression. We also investigate the effect of a fluctuating photo-ionizing background using a simplified model and find that such fluctuations do add smooth power on large scales. The acoustic peak position is, however, unaffected for small amplitude fluctuations (<10%). Larger amplitude fluctuations make the recovery of the BAO signal more difficult and may degrade the achievable significance of the measurement.