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Inhomogeneous Reionization and the Polarization of the Cosmic Microwave Background
The Astrophysical Journal
|November 24, 1999
Summary
Inhomogeneous reionization creates a subtle cosmic microwave background polarization signal. While undetectable by Planck, future high-accuracy experiments may detect this signature of early universe ionization.
Area of Science:
- Cosmology
- Astrophysics
- Early Universe Physics
Background:
- The early universe underwent a phase transition called reionization, where neutral hydrogen became ionized.
- The cosmic microwave background (CMB) polarization anisotropy contains information about this epoch.
- Inhomogeneous reionization, with its patchy structure, is predicted to leave a secondary signal in the CMB.
Purpose of the Study:
- To investigate the secondary polarization anisotropy signal generated by inhomogeneous reionization.
- To assess the detectability of this signal with current and future experiments.
Main Methods:
- Utilized a simple model of inhomogeneous reionization.
- Calculated the resulting second-order signal in CMB polarization anisotropy.
- Compared the predicted signal strength to the sensitivity limits of the Planck Surveyor mission and cosmic variance.
Main Results:
- The predicted secondary signal from inhomogeneous reionization is below Planck's detection limits.
- However, the signal strength exceeds the fundamental cosmic variance limit.
- This indicates the signal is theoretically present but requires enhanced sensitivity for observation.
Conclusions:
- A simple inhomogeneous reionization model produces a secondary CMB polarization signal.
- Current missions like Planck are insufficient for detection.
- Future high-accuracy experiments focusing on subarcminute scales could potentially detect this signal, providing insights into reionization physics.