TY - JOUR
T1 - Results from EDGES High-band. I. Constraints on Phenomenological Models for the Global 21 cm Signal
AU - Monsalve, Raul A.
AU - Rogers, Alan E.E.
AU - Bowman, Judd
AU - Mozdzen, Thomas J.
N1 - Funding Information:
We are grateful to the reviewer for useful suggestions that improved this paper. We also thank Jordan Mirocha for producing the cold IGM reionization models and for valuable feedback. We finally thank Rennan Barkana, Jack Burns, Steve Furlanetto, Adrian Liu, David Rapetti, Peter Sims, and Keith Tauscher for insightful discussions. This work was supported by the NSF through research awards for the Experiment to Detect the Global EoR Signature (AST-0905990, AST-1207761, and AST-1609450). R.M. acknowledges support from the NASA Ames Research Center (NNX16AF59G). EDGES is located at the Murchison Radio-astronomy Observatory. We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. We thank CSIRO for providing site infrastructure and support.
PY - 2017/9/20
Y1 - 2017/9/20
N2 - We report constraints on the global 21 cm signal due to neutral hydrogen at redshifts 14.8 ≥ z ≥ 6.5. We derive our constraints from low-foreground observations of the average sky brightness spectrum conducted with the EDGES High-band instrument between 2015 September 7 and October 26. Observations were calibrated by accounting for the effects of antenna beam chromaticity, antenna and ground losses, signal reflections, and receiver parameters. We evaluate the consistency between the spectrum and phenomenological models for the global 21 cm signal. For tanh-based representations of the ionization history during the epoch of reionization, we rule out, at ≥2s significance, models with duration of up to Δz = 1 at z ≈ 8.5 and higher than Δz = 0.4 across most of the observed redshift range under the usual assumption that the 21 cm spin temperature is much larger than the temperature of the cosmic microwave background during reionization. We also investigate a cold intergalactic medium (IGM) scenario that assumes perfect Lyα coupling of the 21 cm spin temperature to the temperature of the IGM, but that the latter is not heated by early stars or stellar remants. Under this assumption, we reject tanh-based reionization models of duration Δz ≲ 2 over most of the observed redshift range. Finally, we explore and reject a broad range of Gaussian models for the 21 cm absorption feature expected in the First Light era. As an example, we reject 100 mK Gaussians with duration (full width at half maximum) Δz ≤ 4 over the range 14.2 ≥ z ≥ 6.5 at ≥2s significance.
AB - We report constraints on the global 21 cm signal due to neutral hydrogen at redshifts 14.8 ≥ z ≥ 6.5. We derive our constraints from low-foreground observations of the average sky brightness spectrum conducted with the EDGES High-band instrument between 2015 September 7 and October 26. Observations were calibrated by accounting for the effects of antenna beam chromaticity, antenna and ground losses, signal reflections, and receiver parameters. We evaluate the consistency between the spectrum and phenomenological models for the global 21 cm signal. For tanh-based representations of the ionization history during the epoch of reionization, we rule out, at ≥2s significance, models with duration of up to Δz = 1 at z ≈ 8.5 and higher than Δz = 0.4 across most of the observed redshift range under the usual assumption that the 21 cm spin temperature is much larger than the temperature of the cosmic microwave background during reionization. We also investigate a cold intergalactic medium (IGM) scenario that assumes perfect Lyα coupling of the 21 cm spin temperature to the temperature of the IGM, but that the latter is not heated by early stars or stellar remants. Under this assumption, we reject tanh-based reionization models of duration Δz ≲ 2 over most of the observed redshift range. Finally, we explore and reject a broad range of Gaussian models for the 21 cm absorption feature expected in the First Light era. As an example, we reject 100 mK Gaussians with duration (full width at half maximum) Δz ≤ 4 over the range 14.2 ≥ z ≥ 6.5 at ≥2s significance.
KW - cosmology: observations
KW - early universe
KW - methods: data analysis
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U2 - 10.3847/1538-4357/aa88d1
DO - 10.3847/1538-4357/aa88d1
M3 - Article
AN - SCOPUS:85030152981
SN - 0004-637X
VL - 847
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 64
ER -