Abstract
The recent low value of Planck Collaboration XLVII integrated optical
depth to Thomson scattering suggests that the reionization occurred
fairly suddenly, disfavouring extended reionization scenarios. This will
have a significant impact on the 21 cm power spectrum. Using a
semi-numerical framework, we improve our model from instantaneous to
include time-integrated ionization and recombination effects, and find
that this leads to more sudden reionization. It also yields larger H II
bubbles that lead to an order of magnitude more 21 cm power on large
scales, while suppressing the small-scale ionization power. Local
fluctuations in the neutral hydrogen density play the dominant role in
boosting the 21 cm power spectrum on large scales, while recombinations
are subdominant. We use a Monte Carlo Markov chain approach to constrain
our model to observations of the star formation rate functions at z = 6,
7, 8 from Bouwens et al., the Planck Collaboration XLVII optical depth
measurements and the Becker & Bolton ionizing emissivity data at z
˜ 5. We then use this constrained model to perform 21 cm
forecasting for Low Frequency Array, Hydrogen Epoch of Reionization
Array and Square Kilometre Array in order to determine how well such
data can characterize the sources driving reionization. We find that the
Mock 21 cm power spectrum alone can somewhat constrain the halo mass
dependence of ionizing sources, the photon escape fraction and ionizing
amplitude, but combining the Mock 21 cm data with other current
observations enables us to separately constrain all these parameters.
Our framework illustrates how the future 21 cm data can play a key role
in understanding the sources and topology of reionization as
observations improve.
Original language | English |
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Pages (from-to) | 122-139 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 468 |
Issue number | 1 |
DOIs | |
Publication status | Published - 17 Feb 2017 |
Keywords / Materials (for Non-textual outputs)
- cosmology: theory
- dark ages
- reionization
- first stars
- early Universe
- galaxies: formation
- galaxies:evolution
- galaxies: high redshift