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Beyond Optical Depth: Future Determination of Ionization History from the Cosmic Microwave Background
D J Watts1, G E Addison1, C L Bennett1
1JHU Department of Physics and Astronomy, 3701 San Martin Drive, Baltimore MD, 21218, USA.
The Astrophysical Journal
|April 8, 2020
Summary
Constraining cosmic reionization history using cosmic microwave background (CMB) polarization is explored. E-mode measurements offer superior constraints on optical depth (τ) compared to TE mode, with future high signal-to-noise data crucial for precision.
Area of Science:
- Cosmology
- Astrophysics
- Cosmic Microwave Background
Background:
- Reionization history impacts the cosmic microwave background (CMB) polarization.
- Understanding reionization is key to comprehending the early universe.
Purpose of the Study:
- To determine the fundamental limits of constraining reionization histories using CMB anisotropy measurements.
- To assess the impact of different CMB polarization modes (TE and EE) on reionization parameter precision.
Main Methods:
- Utilizing low-noise, full-sky CMB temperature and E-mode polarization data.
- Employing a two-step reionization model with parameters for early and late ionization.
- Projecting constraints on reionization history from CMB angular power spectra.
Main Results:
- CMB E-mode power spectra (CℓEE) provide four times the constraining power on optical depth (τ) compared to TE power spectra (CℓTE).
- Including TE data improves τ precision by 20% over using EE data alone.
- High signal-to-noise measurements at multipoles 10 ⩽ ℓ < 20 are vital for resolving degeneracies in reionization models.
Conclusions:
- Future CMB experiments with sensitivities around 10 µK-arcmin are well-suited for precise reionization studies.
- Accurate constraints on reionization history are achievable with current and near-future CMB observational capabilities.
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