Abstract
We present LIMFAST, a semi-numerical code for computing the progress of
reionization and line intensity mapping signals self-consistently, over large
cosmological volumes and in short computational times. LIMFAST builds upon and
extends the 21cmFAST code by implementing modern galaxy formation and evolution
models. Furthermore, LIMFAST makes use of precomputed stellar population
synthesis and photoionization results to obtain ensemble ionizing and line
emission fields on large scales that vary with redshift, following the
evolution of galaxy properties. We show LIMFAST calculations for the redshift
evolution of the cosmic star formation rate, hydrogen neutral fraction, and
metallicity in galaxies during reionization, which agree with current
observational constraints. We also display the average signal with redshift, as
well as the auto-power spectra at various redshifts, for the 21 cm line, the
Ly$\alpha$ intergalactic and background emission, and the Ly$\alpha$,
H$\alpha$, H$\beta$, OII $3727$A, and OIII $5007$A line emission
from star formation. Overall, the LIMFAST results agree with calculations from
other intensity mapping models, especially with those that account for the
contribution of small halos during reionization. We further discuss the impact
of considering redshift-space distortions, the use of local luminosity and star
formation relations, and the dependence of line emission on the ionization
parameter value. LIMFAST aims at being a resourceful tool for a broad range of
intensity mapping studies, enabling the exploration of a variety of galaxy
evolution and reionization scenarios and frequencies over large volumes in a
short time scale.
Description
LIMFAST. I. A Semi-Numerical Tool for Line Intensity Mapping
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