PRIYA: a new suite of Lyman- α forest simulations for cosmology

We present the PRIYA suite of cosmological simulations, based on the code and hydrodynamic model of the ASTRID simulation, and designed for cosmological analyses of the Lyman- alpha forest. Our simulation suite spans a 9-dimensional parameter space, including 4 cosmological parameters and 5 astrophysical/thermal parameters. We have run 48 low fidelity simulations with 1536(3) particles in a 120 Mpc/h box and 3 high fidelity simulations with 3072(3) particles in a 120 Mpc/h box. All our simulations include a full physics model for galaxy formation, including supernova and AGN feedback, and thus also contain a realistic population of DLAs. We advance on earlier simulations suites by larger particle loads, by incorporating new physical models for patchy hydrogen and helium reionization, and by self-consistently incorporating a model for AGN feedback. We show that patchy helium reionization imprints an excess in the 1D flux power spectrum on large scales, which may allow future measurements of helium reionization bubble sizes. Simulation parameters are chosen based on a Latin hypercube design and a Gaussian process is used to interpolate to arbitrary parameter combinations. We build a multi-fidelity emulator for the 1D flux power spectrum and the mean IGM temperature. We show that our final interpolation error is < 1% and that our simulations produce a flux power spectrum converged at the percent level for z = 5.4-2.2. Our simulation suite will be used to interpret Lyman- a forest 1D flux power spectra from SDSS and future DESI data releases.