21CMMC: an MCMC analysis tool enabling astrophysical parameter studies
  of the cosmic 21 cm signal
  We introduce 21CMMC: a parallelized, Monte Carlo Markov Chain analysis tool,
incorporating the epoch of reionization (EoR) seminumerical simulation
21CMFAST. 21CMMC estimates astrophysical parameter constraints from 21 cm EoR
experiments, accommodating a variety of EoR models, as well as priors on model
parameters and the reionization history. To illustrate its utility, we consider
two different EoR scenarios, one with a single population of galaxies (with a
mass-independent ionizing efficiency) and a second, more general model with two
different, feedback-regulated populations (each with mass-dependent ionizing
efficiencies). As an example, combining three observations (z=8, 9 and 10) of
the 21 cm power spectrum with a conservative noise estimate and uniform model
priors, we find that interferometers with specifications like the Low Frequency
Array/Hydrogen Epoch of Reionization Array (HERA)/Square Kilometre Array 1
(SKA1) can constrain common reionization parameters: the ionizing efficiency
(or similarly the escape fraction), the mean free path of ionizing photons and
the log of the minimum virial temperature of star-forming haloes to within
45.3/22.0/16.7, 33.5/18.4/17.8 and 6.3/3.3/2.4 per cent, ~$1\sigma$ fractional
uncertainty, respectively. Instead, if we optimistically assume that we can
perfectly characterize the EoR modelling uncertainties, we can improve on these
constraints by up to a factor of ~few. Similarly, the fractional uncertainty on
the average neutral fraction can be constrained to within $\lesssim10$ per cent
for HERA and SKA1. By studying the resulting impact on astrophysical
constraints, 21CMMC can be used to optimize (i) interferometer designs; (ii)
foreground cleaning algorithms; (iii) observing strategies; (iv) alternative
statistics characterizing the 21 cm signal; and (v) synergies with other
observational programs.
