Particle mesh simulations of the Lyman-alpha forest and the signature of Baryon Acoustic Oscillations in the intergalactic medium

TL;DR

This paper uses large-scale particle-mesh simulations to study the imprint of baryon acoustic oscillations in the Lyman-alpha forest, providing insights into the intergalactic medium and aiding future observational efforts.

Contribution

It introduces ultra-large particle-mesh simulations that resolve the Jeans scale while capturing BAO features in the intergalactic medium for the first time.

Findings

Detection of BAO in the Lyman-alpha forest correlation function

Simulated spectra match observed flux PDFs and power spectra

Publicly available spectra for testing and planning experiments

Abstract

We present a set of ultra-large particle-mesh simulations of the LyA forest targeted at understanding the imprint of baryon acoustic oscillations (BAO) in the inter-galactic medium. We use 9 dark matter only simulations which can, for the first time, simultaneously resolve the Jeans scale of the intergalactic gas while covering the large volumes required to adequately sample the acoustic feature. Mock absorption spectra are generated using the fluctuating Gunn-Peterson approximation which have approximately correct flux probability density functions (PDFs) and small-scale power spectra. On larger scales there is clear evidence in the redshift space correlation function for an acoustic feature, which matches a linear theory template with constant bias. These spectra, which we make publicly available, can be used to test pipelines, plan future experiments and model various physical effects. As an illustration we discuss the basic properties of the acoustic signal in the forest, the scaling of errors with noise and source number density, modified statistics to treat mean flux evolution and misestimation, and non-gravitational sources such as fluctuations in the photo-ionizing background and temperature fluctuations due to HeII reionization.