RELIKE: Reionization Effective Likelihood from Planck 2018 Data

Abstract

We release RELIKE (Reionization Effective Likelihood), a fast and accurate effective likelihood code based on the latest Planck 2018 data that allows one constrain any model for reionization between $6<z<30$ using five constraints from the CMB reionization principal components (PC). We tested the code on two example models which showed excellent agreement with sampling the exact Planck likelihoods using either a simple Gaussian PC likelihood or its full kernel density estimate. This code enables a fast and consistent means for combining Planck constraints with other reionization data sets, such as kinetic Sunyaev-Zeldovich effects, line-intensity mapping, luminosity function, star formation history, quasar spectra, etc, where the redshift dependence of the ionization history is important. Since the PC technique tests any reionization history in the given range, we also derive model-independent constraints for the total Thomson optical depth ${\tau }_{\mathrm{PC}}=0.0619_{-0.0068}^{+0.0056}$ and its $15\le z\le 30$ high redshift component ${\tau }_{\mathrm{PC}}(15,30)<0.020$ (95\% C.L.). The upper limits on the high-redshift optical depth is a factor of $\sim 3$ larger than those reported in the Planck 2018 cosmological parameter paper using the FlexKnot method and we validate our results with a direct analysis of a two-step model which permits this small high-$z$ component.

15 pages, 14 figures

References in corpus (5)

• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal
• LiteBIRD: JAXA's new strategic L-class mission for all-sky surveys of cosmic microwave background polarization
• Cosmological Information from Lensed CMB Power Spectra
• Reionization inference from the CMB optical depth and E-mode polarization power spectra
• Reionization constraints from five-year WMAP data

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• Crucial Factors for Lyα Transmission in the Reionizing Intergalactic Medium: Infall Motion, HII Bubble Size, and Self-shielded Systems
• 21cmEMU: an emulator of 21cmFAST summary observables
• What it Takes to Measure Reionization with Fast Radio Bursts
• Dispu$\tau$able: the high cost of a low optical depth
• Statistical analysis of the causes of excess variance in the 21 cm signal power spectra obtained with the Low-Frequency Array
• Probing the Early History of Cosmic Reionization by Future Cosmic Microwave Background Experiments
• Reconstructing the epoch of reionisation with Planck PR4
• Simulation based inference of the ionization history from the 2D 21 cm power spectrum
• A New Boundary Condition on Reionization
• Reionization process dependence of the ratio of CMB polarization power spectra at low-$\ell$