A Space-based Observational Strategy for Characterizing the First Stars and Galaxies Using the Redshifted 21cm Global Spectrum
File(s)
Published version
OA Location
Author(s)
Type
Journal Article
Abstract
The redshifted 21 cm monopole is expected to be a powerful probe of the epoch of the first stars and galaxies ($10\lt z\lt 35$). The global 21 cm signal is sensitive to the thermal and ionization state of hydrogen gas and thus provides a tracer of sources of energetic photons—primarily hot stars and accreting black holes—which ionize and heat the high redshift intergalactic medium (IGM). This paper presents a strategy for observations of the global spectrum with a realizable instrument placed in a low-altitude lunar orbit, performing night-time 40–120 MHz spectral observations, while on the farside to avoid terrestrial radio frequency interference, ionospheric corruption, and solar radio emissions. The frequency structure, uniformity over large scales, and unpolarized state of the redshifted 21 cm spectrum are distinct from the spectrally featureless, spatially varying, and polarized emission from the bright foregrounds. This allows a clean separation between the primordial signal and foregrounds. For signal extraction, we model the foreground, instrument, and 21 cm spectrum with eigenmodes calculated via Singular Value Decomposition analyses. Using a Markov Chain Monte Carlo algorithm to explore the parameter space defined by the coefficients associated with these modes, we illustrate how the spectrum can be measured and how astrophysical parameters (e.g., IGM properties, first star characteristics) can be constrained in the presence of foregrounds using the Dark Ages Radio Explorer (DARE).
Date Issued
2017-07-19
Date Acceptance
2017-06-05
Citation
ASTROPHYSICAL JOURNAL, 2017, 844 (1)
ISSN
0004-637X
Publisher
IOP PUBLISHING LTD
Journal / Book Title
ASTROPHYSICAL JOURNAL
Volume
844
Issue
1
Copyright Statement
© 2017 The American Astronomical Society. All rights reserved.
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000405906300009&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
cosmology: observations
dark ages, reionization, first stars
X-RAY-EMISSION
LOW-FREQUENCY OBSERVATIONS
RADIO RECOMBINATION LINES
GROUND-BASED DETECTION
SIMILAR-TO 20
21-CM SIGNAL
COSMIC DAWN
INTERSTELLAR-MEDIUM
DARK-AGES
DECAMETER WAVELENGTHS
0201 Astronomical And Space Sciences
0305 Organic Chemistry
0306 Physical Chemistry (Incl. Structural)
Publication Status
Published
Article Number
ARTN 33