21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal

• Published in: Monthly notices of the Royal Astronomical Society Vol. 449; no. 4; p. 4246
• Main Authors: Greig, Bradley, Mesinger, Andrei
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01.06.2015
• Subjects: Algorithms; Arrays; Astronomical models; Astronomy; Astrophysics; Computer simulation; Estimates; Interferometers; Markov analysis; Mathematical models; Monte Carlo simulation; Noise; Uncertainty
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv571

We introduce 21 CMMC: a parallelized, Monte Carlo Markov Chain analysis tool, incorporating the epoch of reionization (EoR) seminumerical simulation 21 CMFAST. 21 CMMC 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, similar to 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 similar to few. Similarly, the fractional uncertainty on the average neutral fraction can be constrained to within less than or equal to 10 per cent for HERA and SKA1. By studying the resulting impact on astrophysical constraints, 21 CMMC 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.