The redshifted 21-cm signal in the EDGES low-band spectrum
  The EDGES collaboration reported the finding of an unexpectedly deep
absorption in the radio background at 78 MHz and interpreted the dip as a first
detection of redshifted 21-cm from Cosmic Dawn. We have attempted an alternate
analysis, 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 $921 \pm
35$ mK. The depth of the 21-cm absorption inferred by the EDGES analysis
required invoking non-standard cosmology or new physics or new sources at
Cosmic Dawn 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 that there exists a residual unmodeled
systematic sinusoidal feature and we explore this possibility further by
examining for any additional 21-cm signal. The data then favors an absorption
with Gaussian model parameters of amplitude $133 \pm 60$ mK, best width at
half-power $9 \pm 3$ MHz and center frequency $72.5 \pm 0.8$ 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. 2017 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.
