Forecasts for the WFIRST High Latitude Survey using the BlueTides simulation

The authors use the BlueTides simulation to predict the properties of the high-z galaxy and active galactic nucleus (AGN) populations for the planned 2200 deg2Wide-Field Infrared Survey Telescope's (WFIRST) High Latitude Survey (HLS). BlueTides is a cosmological hydrodynamic simulation, which incorporates a variety of baryon physics in a (400 h−1 Mpc)3 volume evolved to z = 8 with 0.7 trillion particles. The galaxy luminosity functions in the simulation show good agreement with all the current observational constraints (up to z = 11) and predict an enhanced number of UV bright galaxies. At the proposed depth of the HLS (mUV < 26.75), BlueTides predicts 106 galaxies at z = 8 with a few up to z ∼ 15 due to the enhanced bright end of the galaxy luminosity function. At z = 8, galaxies in the mock HLS have specific star formation rates of ∼10 Gyr−1 and ages of ∼80 Myr (both evolving linearly with redshift) and a non-evolving mass–metallicity relation. BlueTides also predicts ∼104 AGN in WFIRST HLS from z = 8 out to z ∼ 14. These AGN host black holes of M ∼ 106–108 M⊙ accreting close to their Eddington luminosity. Galaxies and AGN have host halo masses of Mhalo ∼ 1011–12 M⊙ and a linear bias b ≈ 13–20. Given the expected galaxy space densities, their high bias and large volume probed, the authors speculate that it may be feasible for WFIRST HLS to detect the baryon acoustic oscillation peak in the galaxy power spectrum out to z = 8–9.