21cmFAST: A Fast, Semi-Numerical Simulation of the High-Redshift 21-cm
  Signal
  We introduce a powerful semi-numeric modeling tool, 21cmFAST, designed to
efficiently simulate the cosmological 21-cm signal. Our code generates 3D
realizations of evolved density, ionization, peculiar velocity, and spin
temperature fields, which it then combines to compute the 21-cm brightness
temperature. Although the physical processes are treated with approximate
methods, we compare our results to a state-of-the-art large-scale hydrodynamic
simulation, and find good agreement on scales pertinent to the upcoming
observations (>~ 1 Mpc). The power spectra from 21cmFAST agree with those
generated from the numerical simulation to within 10s of percent, down to the
Nyquist frequency. We show results from a 1 Gpc simulation which tracks the
cosmic 21-cm signal down from z=250, highlighting the various interesting
epochs. Depending on the desired resolution, 21cmFAST can compute a redshift
realization on a single processor in just a few minutes. Our code is fast,
efficient, customizable and publicly available, making it a useful tool for
21-cm parameter studies.
