Results from EDGES High-Band: III. New Constraints on Parameters of the Early Universe. (arXiv:1901.10943v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Monsalve_R/0/1/0/all/0/1">Raul A. Monsalve</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fialkov_A/0/1/0/all/0/1">Anastasia Fialkov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bowman_J/0/1/0/all/0/1">Judd D. Bowman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rogers_A/0/1/0/all/0/1">Alan E. E. Rogers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mozdzen_T/0/1/0/all/0/1">Thomas J. Mozdzen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cohen_A/0/1/0/all/0/1">Aviad Cohen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barkana_R/0/1/0/all/0/1">Rennan Barkana</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mahesh_N/0/1/0/all/0/1">Nivedita Mahesh</a>
We present new constraints on parameters of cosmic dawn and the epoch of
reionization derived from the EDGES High-Band spectrum ($90-190$ MHz). The
parameters are probed by evaluating global $21$ cm signals generated with the
recently developed Global21cm tool. This tool uses neural networks trained and
tested on $sim 30,000$ spectra produced with semi-numerical simulations that
assume the standard thermal evolution of the cosmic microwave background and
the intergalactic medium. From our analysis, we constrain at $68%$ (1) the
minimum virial circular velocity of star-forming halos to $V_{rm c}<19.3$ km
s$^{-1}$, (2) the X-ray heating efficiency of early sources to $f_{rm
X}>0.0042$, and (3) the low-energy cutoff of the X-ray spectral energy
distribution to $nu_{rm min}<2.3$ keV. We also constrain the star-formation
efficiency ($f_*$), the electron scattering optical depth ($tau_{rm e}$), and
the mean-free path of ionizing photons ($R_{rm mfp}$). We re-compute the
constraints after incorporating into the analysis four estimates for the
neutral hydrogen fraction from high-$z$ quasars and galaxies, and a prior on
$tau_{rm e}$ from Planck $2018$. The largest impact of the external
observations is on the parameters that most directly characterize reionization.
Specifically, we derive the combined $68%$ constraints $tau_{rm e}<0.063$
and $R_{rm mfp}>27.5$ Mpc. The external observations also have a significant
effect on $V_{rm c}$ due to its degeneracy with $tau_{rm e}$, while the
constraints on $f_*$, $f_{rm X}$, and $nu_{rm min}$, remain primarily
determined by EDGES.
We present new constraints on parameters of cosmic dawn and the epoch of
reionization derived from the EDGES High-Band spectrum ($90-190$ MHz). The
parameters are probed by evaluating global $21$ cm signals generated with the
recently developed Global21cm tool. This tool uses neural networks trained and
tested on $sim 30,000$ spectra produced with semi-numerical simulations that
assume the standard thermal evolution of the cosmic microwave background and
the intergalactic medium. From our analysis, we constrain at $68%$ (1) the
minimum virial circular velocity of star-forming halos to $V_{rm c}<19.3$ km
s$^{-1}$, (2) the X-ray heating efficiency of early sources to $f_{rm
X}>0.0042$, and (3) the low-energy cutoff of the X-ray spectral energy
distribution to $nu_{rm min}<2.3$ keV. We also constrain the star-formation
efficiency ($f_*$), the electron scattering optical depth ($tau_{rm e}$), and
the mean-free path of ionizing photons ($R_{rm mfp}$). We re-compute the
constraints after incorporating into the analysis four estimates for the
neutral hydrogen fraction from high-$z$ quasars and galaxies, and a prior on
$tau_{rm e}$ from Planck $2018$. The largest impact of the external
observations is on the parameters that most directly characterize reionization.
Specifically, we derive the combined $68%$ constraints $tau_{rm e}<0.063$
and $R_{rm mfp}>27.5$ Mpc. The external observations also have a significant
effect on $V_{rm c}$ due to its degeneracy with $tau_{rm e}$, while the
constraints on $f_*$, $f_{rm X}$, and $nu_{rm min}$, remain primarily
determined by EDGES.
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