The Redshifted 21 cm Signal in the EDGES Low-band Spectrum
TLDR
In this paper, a joint fit to the spectrum using such a function together with a flattened absorption profile yields a best-fit absorption amplitude of 921 ± 35 mK, which is consistent with standard cosmology and astrophysics, without invoking excess radio backgrounds or baryon-dark matter interactions.Abstract:
The EDGES collaboration reported an unexpectedly deep absorption in the radio background at 78 MHz and interpreted the dip as the first detection of a redshifted 21 cm signal from cosmic dawn (CD). We attempt an alternate analysis by adopting a maximally smooth function approach to model the foreground. A joint fit to the spectrum using such a function together with a flattened absorption profile yields a best-fit absorption amplitude of 921 ± 35 mK. The depth of the 21 cm absorption inferred by the EDGES analysis required invoking nonstandard cosmology, or new physics, or new sources at CD, and this tension with accepted models is compounded by our analysis that suggests absorption of greater depth. Alternatively, the measured spectrum may be equally well fit assuming there exists a residual unmodeled systematic sinusoidal feature, and we explore this possibility further by examining for additional 21 cm signal. The data then favor an absorption with Gaussian model parameters of amplitude 133 ± 60 mK, best width at half-power 9 ± 3 MHz, and center frequency 72.5 ± 0.8 MHz. We also examine the consistency of the measured spectrum with plausible redshifted 21 cm models: a set of 3 of the 265 profiles in the global 21 cm atlas of Cohen et al. are favored by the spectrum. We conclude that the EDGES data may be consistent with standard cosmology and astrophysics, without invoking excess radio backgrounds or baryon–dark matter interactions.read more
Citations
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Testing for calibration systematics in the EDGES low-band data using Bayesian model selection
Peter Sims,Jonathan C. Pober +1 more
TL;DR: In this paper, a Bayesian evidence-based comparison of models of the EDGES low-band data set is performed, and the subset of the best fitting models that include a global signal favour an amplitude consistent with standard cosmological assumptions (A < 209 mK).
Journal ArticleDOI
Constraining the intergalactic medium at z ≍ 9.1 using LOFAR Epoch of Reionization observations
Raghunath Ghara,Raghunath Ghara,Raghunath Ghara,Sambit K. Giri,Sambit K. Giri,Garrelt Mellema,B. Ciardi,Saleem Zaroubi,Saleem Zaroubi,I. T. Iliev,Léon V. E. Koopmans,Emma Chapman,Simon Gazagnes,B. K. Gehlot,B. K. Gehlot,Abhik Ghosh,Abhik Ghosh,Vibor Jelić,Florent Mertens,Florent Mertens,Rajesh Mondal,Joop Schaye,M. B. Silva,K. M. B. Asad,R. Kooistra,Maaijke Mevius,A. R. Offringa,V. N. Pandey,Sarod Yatawatta +28 more
TL;DR: In this paper, the authors derived constraints on the thermal and ionization states of the intergalactic medium at redshift ≈ 9.1 using new upper limits on the 21-cm power spectrum measured by the LOFAR radio telescope and a prior on the ionized fraction at that redshift estimated from recent cosmic microwave background (CMB) observations.
Journal ArticleDOI
On the detection of a cosmic dawn signal in the radio background
TL;DR: In this article , a radiometer measurement of the spectrum of the radio sky in the 55-85 MHz band, which shows that the profile found by Bowman et al. in data taken with the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) low-band instrument is not of astrophysical origin; their best-fitting profile is rejected with 95.3% confidence.
Journal ArticleDOI
Tight constraints on the excess radio background at z = 9.1 from LOFAR
Rajesh Mondal,Rajesh Mondal,Anastasia Fialkov,C. Fling,Ilian T. Iliev,Rennan Barkana,B. Ciardi,Garrelt Mellema,Saleem Zaroubi,Saleem Zaroubi,Saleem Zaroubi,Luitje Koopmans,Florent Mertens,B. K. Gehlot,Raghunath Ghara,Raghunath Ghara,Raghunath Ghara,Abhik Ghosh,Sambit K. Giri,Sambit K. Giri,A. R. Offringa,Vishambhar Pandey,Vishambhar Pandey +22 more
TL;DR: In this paper, the authors used the upper limit on the 21-cm signal from the Epoch of Reionization (z = 9.1) based on 141 h of observations with LOFAR to evaluate the contribution of the high-redshift Universe to the detected radio background.
Journal ArticleDOI
The Radio Scream from black holes at Cosmic Dawn: a semi-analytic model for the impact of radio-loud black holes on the 21 cm global signal
TL;DR: In this paper, a semi-analytic model was used to explore the potential impact of a brief and violent period of radio-loud accretion onto black-holes (The Radio Scream) during the Cosmic Dawn on the HI hyperfine 21 cm signal.
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