Planting a Lyman alpha forest on ABACUSSUMMIT

The full-shape correlations of the Lyman alpha (Ly a) forest contain a wealth of cosmological information through the Alcock-Paczynski effect. However, these measurements are challenging to model without robustly testing and verifying the theoretical framework used for analysing them. Here, we leverage the accuracy and volume of the N-body simulation suite AbacusSummit to generate high-resolution Ly a skewers and quasi-stellar object (QSO) catalogues. One of the main goals of our mocks is to aid in the full-shape Ly a analysis planned by the Dark Energy Spectroscopic Instrument (DESI) team. We provide optical depth skewers for six of the fiducial cosmology base-resolution simulations (L-box} = 2h(-1), N = 6912(3)) at z = 2.5. We adopt a simple recipe based on the Fluctuating Gunn-Peterson Approximation (FGPA) for constructing these skewers from the matter density in an N-body simulation and calibrate it against the 1D and 3D Ly a power spectra extracted from the hydrodynamical simulation IllustrisTNG (TNG L-box} = 205, h(-1), N = 2500(3)). As an important application, we study the non-linear broadening of the baryon acoustic oscillation (BAO) peak and show the cross-correlation between DESI-like QSOs and our Ly a forest skewers. We find differences on small scales between the Kaiser approximation prediction and our mock measurements of the Ly a x QSO cross-correlation, which would be important to account for in upcoming analyses. The AbacusSummit Ly a forest mocks open up the possibility for improved modelling of cross-correlations between Ly a and cosmic microwave background (CMB) lensing and Ly a and QSOs, and for forecasts of the 3-point Ly a correlation function. Our catalogues and skewers are publicly available on Globus via the National Energy Research Scientific Computing Center (NERSC) (full link under the section 'Data Availability').