Formulating and Critically Examining the Assumptions of Global 21 cm Signal Analyses: How to Avoid the False Troughs That Can Appear in Single-spectrum Fits

@article{Tauscher2020FormulatingAC,
  title={Formulating and Critically Examining the Assumptions of Global 21 cm Signal Analyses: How to Avoid the False Troughs That Can Appear in Single-spectrum Fits},
  author={Keith Tauscher and David Rapetti and Jack O. Burns},
  journal={arXiv: Cosmology and Nongalactic Astrophysics},
  year={2020}
}
The assumptions inherent to global 21-cm signal analyses are rarely delineated. In this paper, we formulate a general list of suppositions underlying a given claimed detection of the global 21-cm signal. Then, we specify the form of these assumptions for two different analyses: 1) the one performed by the EDGES team showing an absorption trough in brightness temperature that they modeled separately from the sky foreground and 2) a new, so-called Minimum Assumption Analysis (MAA), that makes the… 

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References

SHOWING 1-10 OF 41 REFERENCES
An absorption profile centred at 78 megahertz in the sky-averaged spectrum
TLDR
The detection of a flattened absorption profile in the sky-averaged radio spectrum that is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions.
REACH: Radio Experiment for the Analysis of Cosmic Hydrogen
The Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) is a new instrument dedicated to the detection of the red-shifted radio signature signal from Hydrogen from the times when the
Global 21 cm Signal Extraction from Foreground and Instrumental Effects. III. Utilizing Drift-scan Time Dependence and Full Stokes Measurements
When using valid foreground and signal models, the uncertainties on extracted signals in global 21-cm signal experiments depend principally on the overlap between signal and foreground models. In
Global 21 cm Signal Extraction from Foreground and Instrumental Effects. II. Efficient and Self-consistent Technique for Constraining Nonlinear Signal Models
TLDR
The spectral constraints derived in the first paper are utilized to calculate the full posterior probability distribution of any signal parameter space of choice and provide the starting point for a Markov Chain Monte Carlo (MCMC) engine that samples the signal without traversing the foreground parameter space.
Transformative science from the lunar farside: observations of the dark ages and exoplanetary systems at low radio frequencies
  • J. Burns
  • Physics, Geology
    Philosophical Transactions of the Royal Society A
  • 2020
TLDR
The astrophysics associated with NASA-funded concept studies will be described including a lunar-orbiting spacecraft, DAPPER, that will measure the 21 cm global spectrum at redshifts ≈40–80, and an array of low frequency dipoles on the lunar farside surface, FARSIDE, that would detect exoplanet magnetic fields.
A Ground Plane Artifact that Induces an Absorption Profile in Averaged Spectra from Global 21 cm Measurements, with Possible Application to EDGES
Most of the current Global 21-cm experiments include ground screens that help moderate effects from the Earth. In this paper, we report on a possible systematic artifact within the ground plane that
Assessment of the Projection-induced Polarimetry Technique for Constraining the Foreground Spectrum in Global 21 cm Cosmology
Detecting the cosmological sky-averaged (global) 21 cm signal as a function of observed frequency will provide a powerful tool to study the ionization and thermal history of the intergalactic medium
Dark Cosmology: Investigating Dark Matter & Exotic Physics in the Dark Ages using the Redshifted 21-cm Global Spectrum
The Dark Ages, probed by the redshifted 21-cm signal, is the ideal epoch for a new rigorous test of the standard LCDM cosmological model. Divergences from that model would indicate new physics, such
Direct millicharged dark matter cannot explain the EDGES signal
Heat transfer between baryons and millicharged dark matter has been invoked as a possible explanation for the anomalous 21-cm absorption signal seen by EDGES. Prior work has shown that the solution
On the contamination of the global 21 cm signal from polarized foregrounds
Global (i.e. sky-averaged) 21 cm signal experiments can measure the evolution of the universe from the Cosmic Dawn to the Epoch of Reionization. These measurements are challenged by the presence of
...
1
2
3
4
5
...