Parametrizations of the 21-cm global signal and parameter estimation from single-dipole experiments
File(s)
Accepted version
Author(s)
Harker, GJA
Mirocha, J
Burns, JO
Pritchard, JR
Type
Journal Article
Abstract
One approach to extracting the global 21-cm signal from total-power measurements at low radio frequencies is to parametrize the different contributions to the data and then fit for these parameters. We examine parametrizations of the 21-cm signal itself, and propose one based on modelling the Ly α background, intergalactic medium temperature and hydrogen ionized fraction using tanh functions. This captures the shape of the signal from a physical modelling code better than an earlier parametrization based on interpolating between maxima and minima of the signal, and imposes a greater level of physical plausibility. This allows less biased constraints on the turning points of the signal, even though these are not explicitly fit for. Biases can also be alleviated by discarding information which is less robustly described by the parametrization, for example by ignoring detailed shape information coming from the covariances between turning points or from the high-frequency parts of the signal, or by marginalizing over the high-frequency parts of the signal by fitting a more complex foreground model. The fits are sufficiently accurate to be usable for experiments gathering 1000 h of data, though in this case it may be important to choose observing windows which do not include the brightest areas of the foregrounds. Our assumption of pointed, single-antenna observations and very broad-band fitting makes these results particularly applicable to experiments such as the Dark Ages Radio Explorer, which would study the global 21-cm signal from the clean environment of a low lunar orbit, taking data from the far side.
Date Issued
2015-12-01
Date Acceptance
2015-11-05
Citation
Monthly Notices of the Royal Astronomical Society, 2015, 455 (4), pp.3829-3840
ISSN
0035-8711
Publisher
Oxford University Press (OUP)
Start Page
3829
End Page
3840
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
455
Issue
4
Copyright Statement
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Sponsor
Imperial College Trust
Science and Technology Facilities Council (STFC)
Commission of the European Communities
Science and Technology Facilities Council [2006-2012]
Grant Number
N/A
ST/K001051/1
638743
ST/K001051/1
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
methods: statistical
cosmology: theory
dark ages, reionization, first stars
diffuse radiation
radio lines: general
COSMIC DAWN
DARK-AGES
COSMOLOGY
MODELS
Publication Status
Published