Forecasts for the WFIRST High Latitude Survey using the BlueTides Simulation

TL;DR

This paper uses the BlueTides simulation to forecast galaxy and AGN populations for the WFIRST High Latitude Survey, predicting millions of high-redshift galaxies and thousands of AGN, and exploring their properties and cosmological implications.

Contribution

It provides the first detailed predictions of high-redshift galaxy and AGN populations for WFIRST HLS using a large hydrodynamic simulation, including luminosity functions and clustering properties.

Findings

Predicts 1 million galaxies at z=8 for WFIRST HLS.

Forecasts around 10,000 AGN from z=8 to z=14.

Suggests potential detection of the BAO peak at z=8-9.

Abstract

We use the BlueTides simulation to predict the properties of the high-$z$ galaxy and active galactic nuclei (AGN) populations for the planned 2200deg$^2$ Wide-Field Infrared Survey Telescope's (WFIRST)-AFTA High Latitude Survey (HLS). BlueTides is a cosmological hydrodynamic simulation, which incorporates a variety of baryon physics in a $(400h^{-1} \mathrm{Mpc})^3$ 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 predicts an enhanced number of UV bright galaxies. At the proposed depth of the HLS ($m < 26.75$), BlueTides predicts $10^6$ galaxies at $z=8$ with a few up to $z\sim 15$ 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 $\sim 10 {\rm Gyr}^{-1}$ and ages of $\sim 80 {\rm Myr}$ (both evolving linearly with redshift) and a non-evolving mass-metallicity relation. BlueTides also predicts $\sim 10^4$ AGN in WFIRST HLS from $z=8$ out to $z\sim 14$. These AGN host black holes of $M\sim 10^6-10^8 M_\odot$ accreting close to their Eddington luminosity. Galaxies and AGN have host halo masses of $M_{halo}\sim 10^{11-12} M_\odot$ and a linear bias $b\approx 13-20$. Given the expected galaxy space densities, their high bias and large volume probed we speculate that it may be feasible for WFIRST HLS detect the Baryon Acoustic Oscillation peak in the galaxy power spectrum out to $z=8-9$.