SCORCH. I. THE GALAXY-HALO CONNECTION IN THE FIRST BILLION YEARS

SCORCH (Simulations and Constructions of the Reionization of Cosmic Hydrogen) is a new project to study the Epoch of Reionization (EoR). In this first paper, we probe the connection between observed high-redshift galaxies and simulated dark matter halos to better understand the primary source of ionizing radiation. High-resolution N-body simulations are run to quantify the abundance of dark matter halos as a function of mass M, accretion rate M., and redshift z. A new fit for the halo mass function dn/dM is approximate to 20% more accurate at the high-mass end. A novel approach is used to fit the halo accretion rate function dn/d(M) over dot in terms of the halo mass function. Abundance matching against the observed galaxy luminosity function is used to estimate the luminosity-mass relation and the luminosity-accretion-rate relation. The inferred star formation efficiency is not monotonic with M nor (M) over dot, but reaches a maximum value at a characteristic mass similar to 2 x 10(11) M-circle dot and a characteristic accretion rate similar to 6 x 10(2) M-circle dot yr(-1) at z approximate to 6. We find a universal EoR luminosity-accretion-rate relation and construct a fiducial model for the galaxy luminosity function. The Schechter parameters evolve such that phi(star) decreases, M-star is fainter, and alpha is steeper at higher redshifts. We forecast for the upcoming James Webb Space Telescope and show that with apparent magnitude limit m(AB) approximate to 31 (32), it can observe greater than or similar to 11 (24) unlensed galaxies per square degree per unit redshift at least down to M-star at z less than or similar to 13 (14).