Fast, large-volume, GPU-enabled simulations for the Lyα forest: power spectrum forecasts for baryon acoustic oscillation experiments

High-redshift measurements of the baryonic acoustic oscillation (BAO) scale from large Lya forest surveys represent the next frontier of dark energy studies. As part of this effort, efficient simulations of the BAO signature from the Lya forest will be required. We construct a model for producing fast, large-volume simulations of the Lya forest for this purpose. Utilizing a calibrated semi-analytic approach, we are able to run very large simulations in 1 Gpc3 volumes which fully resolve the Jeans scale in less than a day on a desktop PC using a graphics processing unit enabled version of our code. The Lya forest spectra extracted from our semi-analytical simulations are in excellent agreement with those obtained from a fully hydrodynamical reference simulation. Furthermore, we find that our simulated data are in broad agreement with observational measurements of the flux probability distribution and 1D flux power spectrum. We are able to correctly recover the input BAO scale from the 3D Lya flux power spectrum measured from our simulated data, and estimate that a Baryon Oscillation Spectroscopic Survey like 104 deg2 survey with similar to 15 background sources per square degree and a signal-to-noise ratio of similar to 5 per pixel should achieve a measurement of the BAO scale to within similar to 1.4 per cent. We also use our simulations to provide simple power-law expressions for estimating the fractional error on the BAO scale on varying the signal-to-noise ratio and the number density of background sources. The speed and flexibility of our approach is well suited for exploring parameter space and the impact of observational and astrophysical systematics on the recovery of the BAO signature from forthcoming large-scale spectroscopic surveys.