The Maximum B-mode Polarization of the Cosmic Microwave Background from Inhomogeneous Reionization

Abstract

We compute the B-mode polarization power spectrum of the CMB from an epoch of inhomogeneous reionization, using a simple model in which HII regions are represented by ionized spherical bubbles with a log normal distribution of sizes whose clustering properties are determined by large-scale structure. Both the global ionization fraction and the characteristic radius of HII regions are allowed to be free functions of redshift. Models that would produce substantial contamination to degree scale gravitational wave B-mode measurements have power that is dominated by the shot noise of the bubbles. Rare bubbles of >100 Mpc at z>20 can produce signals that in fact exceed the B-modes from gravitational lensing and are comparable to the maximal allowed signal of gravitational waves (~0.1uK) while still being consistent with global constraints on the total optical depth. Even bubbles down to 20 Mpc at z~15, or 40 Mpc at z~10 can be relevant (0.01uK) once the lensing signal is removed either statistically or directly. However, currently favored theoretical models that have ionization bubbles that only grow to such sizes at the very end of a fairly prompt and late reionization produce signals which are at most at these levels.

14 pages, 11 figures; published in ApJ; corrected Fig. 4 and updated references

References in corpus (3)

• Observational constraints on Cosmic Reionization
• Implications of WMAP 3 Year Data for the Sources of Reionization
• Lyman Limit Systems in Cosmological Simulations

Cited by in corpus (13)

• Reconstructing Patchy Reionization from the Cosmic Microwave Background
• Secondary anisotropies of the CMB
• Effect of the intergalactic environment on the observability of Ly-alpha emitters during reionization
• B-mode CMB Polarization from Patchy Screening during Reionization
• The Signature of Patchy Reionization in the Polarization Anisotropy of the CMB
• Approximate Analytic Spectra of Reionized CMB Anisotropies and Polarization generated by Relic Gravitational Waves
• Reconstructing the Thomson Optical Depth due to Patchy Reionization with 21-cm Fluctuation Maps
• Is patchy reionization an obstacle in detecting the primordial gravitational wave signal?
• Inference of gravitational lensing and patchy reionization with future CMB data
• Observational Limits on Patchy Reionization: Implications for B-modes
• A framework to mitigate patchy reionization contamination on the primordial gravitational wave signal
• Secondary B-mode polarization from Faraday rotation in clusters and galaxies
• Reconstructing patchy helium reionization using the cosmic microwave background and large-scale structure