Reionization process dependence of the ratio of CMB polarization power spectra at low-$\ell$

Abstract

We investigate how much the ratio of cosmic microwave background (CMB) polarization power spectra $C_{\ell }^{BB}/C_{\ell }^{EE}$ at low-$\ell$ ($\ell \lesssim 10$) depends on the process of reionization. Both such low-$\ell$ B-mode and E-mode polarization powers are dominantly produced by Thomson scattering of CMB photons off the free electrons which are produced in the process of reionization. Since the reionization should be finished until at least the redshift $z\simeq 6$ and the low-$\ell$ polarization powers are produced at late time, the ratio is rather insensitive by the ionization process at higher redshifts, but it is sensitive to the value of optical depth.The value of the ratio at $\ell =2$, however, is almost insensitive to the reionization process including the value of optical depth, and the value is approximately half of the value of tensor-to-scalar ratio. This fact can be utilized for future determination of tensor-to-scalar ratio in spite of the ambiguity due to cosmic variance.

arXiv comment19 pages, 9 figures

References in corpus (24)

• Efficient Computation of CMB anisotropies in closed FRW models
• Statistics of Cosmic Microwave Background Polarization
• Planck intermediate results. XLVII. Planck constraints on reionization history
• Cosmic Microwave Background Fluctuations from Gravitational Waves: An Analytic Approach
• Analytic approach to the polarization of the cosmic microwave background in flat and open universes
• LiteBIRD: JAXA's new strategic L-class mission for all-sky surveys of cosmic microwave background polarization
• Reionization and galaxy inference from the high-redshift Lyα forest
• Large Angular Scale Polarization of the Cosmic Microwave Background and the Feasibility of its Detection
• Analytic approach to the CMB polarizations generated by relic gravitational waves
• Studying the Lyman-$\alpha$ optical depth fluctuations at $z\sim 5.5$ using fast semi-numerical methods
• Complete Reionization Constraints from Planck 2015 Polarization
• Polarization of the Microwave Background in Inflationary Cosmology
• Reionization inference from the CMB optical depth and E-mode polarization power spectra
• Signatures of metal-free star formation in Planck 2015 Polarization Data
• Large-angle Polarization of the Cosmic Microwave Background Radiation and Reionization
• Cosmic Reionization May Still Have Started Early and Ended Late: Confronting Early Onset with CMB Anisotropy and 21 cm Global Signals
• RELIKE: Reionization Effective Likelihood from Planck 2018 Data
• Joining bits and pieces of reionization history
• Large-scale Polarization of the Cosmic Microwave Background Radiation
• The high-redshift tail of stellar reionization in LCDM is beyond the reach of the low-$\ell$ CMB
• Dark Twilight Joined with the Light of Dawn to Unveil the Reionization History
• Extended reionization in models beyond $\Lambda$CDM with Planck 2018 data
• On CMB B-modes and the Onset of Inflation
• Polarizations of CMB and the Hubble tension