Zusammenfassung
Current standard astrophysical models struggle to explain the tentative
detection of the 21 cm absorption trough centered at $z\sim17$ measured by the
EDGES low-band antenna. However, it has been shown that the EDGES results are
consistent with an extrapolation of a declining UV luminosity density,
following a simple power-law of deep Hubble Space Telescope observations of $4
< z < 9$ galaxies. We here explore the conditions by which the EDGES detection
is consistent with current reionization and post-reionization observations,
including the volume-averaged neutral hydrogen fraction of the intergalactic
medium at $z\sim6-8$, the optical depth to the cosmic microwave background, and
the integrated ionizing emissivity at $z\sim5$. By coupling a physically
motivated source model derived from radiative transfer hydrodynamic simulations
of reionization to a Markov Chain Monte Carlo sampler, we find that high
contribution from low-mass halos along with high photon escape fractions are
required to simultaneously reproduce the high-redshift (cosmic dawn) and
low-redshift (reionization) existing constraints. Low-mass faint-galaxies
dominated models produce a flatter emissivity evolution that results in an
earlier onset of reionization with gradual and longer duration, and higher
optical depth. Our results provide insights on the role of faint and bright
galaxies during cosmic reionization, which can be tested by upcoming surveys
with the James Webb Space Telescope.
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